![8 MERCURY CYCLING IN THE ENVIRONMENT
fish, which were a staple of the local diet. In the following
years, more than 100 people died and more than 1000 were
permanently disabled from the resulting methylmercury
poisoning, which consequently bears the name, Minimata
Disease (Clarkson, 1997).
It is also important to note that, by definition, the
increased deposition (of RGM and particulate-bound Hg)
to oceans and lakes throughout the globe as compared with
preindustrial times is ultimately attributable to anthropo-
genic activities. Though the input occurs after transport
through the atmosphere, it is nonetheless of anthropogenic
origin.
Mining Runoff
An additional important source of mercury to aquatic
systems is runoff or leaching resulting from mining
activities. Large-scale mercury mines often produce large
quantities of tailings or leave mining passages open
after operations cease (e.g., Sulfur Bank Mercury Mine,
California [Engle et al., 2007]; Almadén, Spain [Gray et al.,
2004]; Idrija, Slovenia [Hines et al., 2006]). Early gold and
silver mining also produced large quantities of Hg-enriched
tailings because Hg was added to crushed ore in order to
amalgamate and extract the gold and silver (e.g., Bonzongo
et al., 1996). The wastes, along with the open mine passages,
allow rain and groundwater to leach and mobilize mercury.
Even smaller-scale mining activities, in particular artisanal
mining practiced in China, Indonesia, South America, and
Africa (reviewed by Veiga et al., 2006) produce significant
amounts of waste matter that is enriched in mercury. This
is often dumped into streams or lakes, or otherwise allowed
to leach in an uncontrolled manner.
Methylated Species
Perhaps the most crucial process in the global cycling of
mercury, at least from the standpoint of toxicity, is the con-
centration and accumulation of MMHg or DMHg up the
food chain (called “bio-accumulation”). Most of the DMHg
and MMHg that is bio-accumulated is produced in situ in
natural waters or near the sediment–water interface. The
production of MMHg and DMHg from dissolved Hg(II)
(methylation) occurs primarily in sulfate-reducing bacteria
in anoxic environments and has been hypothesized to be
a cellular detoxification mechanism. A limited number of
other methylation mechanisms have been proposed, but
bacteria appear to be the largest producers in lakes and
wetlands (Rudd, 1995; Fitzgerald et al., 2007).
Little DMHg and MMHg is found in the surface waters
of the open ocean. Higher concentrations of DMHg can be
found below the mixed layer of the open ocean and periph-
eral seas, while MMHg has been unambiguously detected
only in coastal zones, peripheral seas, and the Equatorial
Pacific Ocean (Fitzgerald et al., 2007).
Sources of Mercury in Water
Atmospheric Wet and Dry Deposition
The largest and most important source of mercury in water is
wet and dry deposition from the atmosphere. This includes
both a natural and anthropogenic component. Globally,
about 1% of the total oceanic burden is deposited and emit-
ted each year (Mason and Sheu, 2002; Sunderland and
Mason, 2007). Most of the mercury deposited to oceans in
precipitation is either bound to particles or is dissolved in an
ionic state, Hg(II). Over the oceans, the overwhelming por-
tion that is dry deposited is RGM, which has been produced
near the water surface from photochemically driven oxida-
tion by halogens (Laurier et al., 2003; Sprovieri et al., 2003;
Laurier and Mason, 2007; Holmes et al., 2009). A portion
(~10%) of the RGM that is deposited to the ocean is reduced
to elemental mercury in the surface waters, either directly by
sunlight, or through biologic activity (Fitzgerald et al., 2007;
Strode et al., 2007). This tends to make the surface waters
supersaturated with respect to dissolved elemental mercury
(Schroeder and Munthe, 1998). Therefore, (gaseous) elemen-
tal mercury is generally evading from the ocean surface.
Lakes and wetlands are more variable in their interaction
with GEM. Some studies have reported supersaturations in
surface waters with net evasion (Poissant et al., 2000, 2004),
and others have observed slow net deposition or near equi-
librium with the air (Zhang and Lindberg, 2000) or diurnal
cycles (Marsik et al., 2005).
Mercury that is bound to particles and bound to soluble
organic complexes can also be incorporated into the hydro-
logic cycle as a part of runoff after rain or flooding events
and through the movement of subsurface pore water.
Subsurface geothermal and hydrothermal vents are also
sources of mercury in the ocean, although the magnitude
of these inputs is believed to be negligible as compared
with the total oceanic burden. Subsurface vents may, none-
theless, be important in enhancing the concentrations in
ambient waters and sediments near the vent site (Stoffers
et al., 1999; King et al., 2006; Lamborg et al., 2006). Some
mercury is also thought to enter (or perhaps reenter) the
hydrologic cycle from diagenetic reactions, which are phys-
ical, chemical, or biologic changes that occur as sediment
(settled particulate matter that contains mercury) is depos-
ited, compressed, and transformed to rock.
Industrial Point Sources
Industrial waste is an important source of Hg to some
watersheds. The most prominent example of anthropo-
genic input of mercury to aquatic system occurred in Mini-
mata, Japan, in the early 1950s. Throughout this period, the
Chisso Corporation dumped more than 20 tons of mercury
that had been used as a catalyst in the production of acet-
aldehyde, into Minamata Bay. The mercury contaminated
the sediments, water, and ecosystem and ultimately the](https://image.slidesharecdn.com/2489511-250625053945-6e71613f/85/Mercury-In-The-Environment-Pattern-And-Process-1st-Edition-Michl-S-Bank-30-320.jpg)
![SOURCES AND TRANSPORT: A GLOBAL ISSUE 13
estimate that coastal benthic MMHg production rates and
diffusional efflux are sufficient that they are likely a major
source to nearby ecosystems and potentially the open ocean.
Atmospheric Transport
DISPERSION OF POINT AND AREA SOURCE PLUMES
The majority of direct anthropogenic mercury emissions
are from point sources such as coal-fired power plants,
municipal waste incinerators, metal refineries, and chlor-
alkali plants. The dispersion of these types of plumes has
been widely studied, and a range of tools exist to describe
the fate of chemicals in those plumes (e.g., Mossio et al.,
2001). GEM emitted from these sources is largely unreac-
tive and has been suggested to be useful tracer of sources
(Friedli et al., 2004; Jaffe et al., 2005). RGM and PHg have
much different fates. RGM is rapidly deposited to particles
and surfaces, and can be sequestered by cloud and rain
drops (Schroeder and Munthe, 1998). Particulate mercury
can also settle out of the atmosphere or become incorpo-
rated into rain and cloud drops. Depending on the ambient
conditions and the chemistry of the emitted plume, some
of the RGM may be reduced to GEM (Lohman et al., 2006).
Thus, if an airmass remains in contact with the surface,
a large fraction of the RGM and PHg will be lost to the
surface within hours to days of emission.
Continental Export and Long-Range Transport
Large, polluted airmasses can be exported from their source
region, and then transported and dispersed over thousands
of kilometers in the jet stream through their interaction
with a midlatitude cyclone. Because the lifetime of GEM in
the atmosphere is about 1 year (Selin et al., 2007), in some
cases plumes have been observed for 7–10 days or more after
emission (Jaffe et al., 2005; Slemr et al., 2006; Ebinghaus
et al., 2007; Weiss-Penzias et al., 2007; Swartzendruber
et al., 2008). In these studies, the mercury source region was
identified through a combination of trajectory and synop-
tic analysis, and the calculation of enhancement ratios of
copollutants. The enhancement ratios reflect the emission
ratio (under certain assumptions) and, because of a signifi-
cant difference in emission ratios between the major emit-
ters (Jaffe et al., 2005; Weiss-Penzias et al., 2007), can sug-
gest a source type. The suggested source type and backward
air-parcel trajectories can then be compared with emissions
maps. This approach has been successful in identifying
intercontinental transport of Hg from sources in East Asia,
Europe, and Africa. Modeling studies have confirmed the
long-range transport of Hg seen in observations (e.g., Selin
et al., 2007; Jaffe and Strode, 2008; Strode et al., 2008).
Global Transport
Once polluted airmasses are lofted into the jet stream, they can
circle the northern hemisphere in as little as 7–10 days and will
is deposited in estuarine regions and oceanic shelves and
does not reach the open ocean. Also, because wetlands can
be strong producers of MMHg, the outflow from wetlands
can be significant sources to downstream water bodies
(St. Louis et al., 1996). One study of fate and transport
in a boreal wetland found that over the course of several
months, significant fractions of a newly deposited isotope
(202Hg) were converted to MMHg and were transported
below the water table and toward a neighboring lake via
groundwater (Branfireun et al., 2005).
Ocean Settling and Transport
The world’s oceans play an important role in transporting
and redistributing heat throughout the globe, but they do
not play as prominent a role for mercury. This is primarily
due to the much shorter intrahemispheric mixing time of
the atmosphere (~10–20 days [Jacob, 1999]) as compared to
the oceans (10s to 1000s of years [Sunderland and Mason,
2007]). Also, the short lifetime of Hg in the surface oceans
against reemission (~0.6 year [Selin et al., 2008]) means
that the surface ocean and atmosphere are in steady
state on an annual time scale. Thus, the atmosphere will
act to damp local perturbations from the surface ocean.
Noteworthy oceanic transport processes include up/down-
welling, interhemispheric transport, particle settling, and
transport of MMHg from coastal sediments.
Mason et al. (1994) estimated that upwelling of thermo-
cline waters in the equatorial Pacific is similar to the net
atmospheric input to the surface, and in some places it may
be greater. This, along with observations of elevated mercury
in subsurface waters (Mason and Fitzgerald, 1993; Mason and
Sullivan, 1999; Horvat et al., 2003) suggests that mercury-
enriched water masses may sink from the surface and be
transported as a record of historical deposition. Nonetheless,
because of the relatively slow exchange rate of the world’s
oceans, the fluxes in and out of intermediate and deep reser-
voirs are a very small fraction of their overall burden.
Oceanic transport also likely contributes to interhemi-
spheric transport. The lifetime of mercury in deep ocean
compartments is much longer, 10s to 1000s of years
(Sunderland and Mason, 2007) than surface reservoirs and
would allow for interhemispheric transport. The impact of
this mercury on atmospheric concentrations and deposi-
tion to land, however, would depend on the deep waters
reaching the surface. The settling of particulate mercury,
from the surface to deep waters and the ocean floor, is an
important component in the oceanic cycle, particularly
in the North Atlantic. In the surface waters, carbon-rich
biomass or waste matter produced by phytoplankton or
zooplankton sequesters mercury and falls to the interme-
diate and deep ocean. It is believed that about 50% of the
sinking mercury is buried on the ocean floor and is lost to
deep reservoirs (Sunderland and Mason, 2007).
The transport of MMHg from coastal sediments is also an
important form of oceanic transport. Fitzgerald et al. (2007)](https://image.slidesharecdn.com/2489511-250625053945-6e71613f/85/Mercury-In-The-Environment-Pattern-And-Process-1st-Edition-Michl-S-Bank-35-320.jpg)
![19
CHAPTER 2
Industrial Use of Mercury in the Ancient World
WILLIAM E. BROOKS
soon replaced mercury brought across the Atlantic from
the centuries-old Almaden Mine in Spain (Putman, 1972).
The slaves and indigenous workers at Huancavelica were
exposed to cinnabar powder from mining, mercury fumes
from mining and retorting, dust that contained silica and
arsenic compounds, cold, high altitude, carbon monoxide,
cave-ins, and poor ventilation; therefore, Huancavelica
came to be known as the “mina de la muerte” [mine of
death] (Brown, 2001).
In Europe in the 1800s, mercury was widely used
for gilding domes and interiors of cathedrals, domes of
government buildings, and religious figures and also for
mirror backing. Mercuric nitrate was widely used for mak-
ing hats, and the term “mad hatter” was associated with
those who were affected by the fumes released during the
process. The term “vermeil” was also used in the 19th cen-
tury; it referred to a sterling silver product, for example, a
wine cooler, with all surfaces coated with a minimum of
10 karat gold that was of a minimum thickness of 2.5 µm;
however, this process was banned because the artisans
became blind as a result of exposure to mercury. Tableware
made by this metallurgical process is kept on display in the
Vermeil Room in the White House, Washington, DC. Along
with polished copper, brass, silver, and obsidian, the reflec-
tive qualities and movement of native mercury made it
intriguing as a scrying, or fortune-telling, mirror. Mercury
has also been used as a mirror to reflect light for transmit-
ted light microscopes.
Powdered cinnabar, or vermillion, was widely used as
an artist’s pigment in Europe from the 1300s until the
1900s (Windhaven Guild, 2004) and is still available from
art suppliers (Iconofile, 2010). Mercury compounds were
used to inhibit mold in some household paints; however,
because of its toxicity, mercury is no longer used for this
application.
THE OLD WORLD AND ASIA
THE NEW WORLD
CONCLUSION
Mercury and cinnabar, the common ore of mercury, were
known and used by ancient people in Africa, Asia, Central
America, Europe, Mexico, and South America. Archaeolo-
gists have shown that cinnabar was mined and mercury was
produced more than 8000 years ago in Turkey. Cinnabar
was a multiuse pigment in many parts of the ancient world,
and mercury was used for gilding or placer gold amalgama-
tion. Mercury was the earliest known treatment for syphilis,
and its use is described in the Canon of Medicine by the
Persian physician Ibn Sina (Avicenna) in 1025 CE.
Even though cinnabar and mercury are found world-
wide, the most well-known occurrences include those in
Almaden, Spain; California; Huancavelica, Peru; Idrija,
Slovenia; the Sizma district, Turkey; and the Yangtze region,
China. The mineral name “cinnabar” may have been
derived from Sinop, also called Cinab, a Black Sea port that
was an export center for cinnabar and mercury (also called
“ruddle”) produced in ancient Turkey (Barnes and Bailey,
1972). An undated Chinese saying “where there is cinnabar
above, yellow gold will be found below” (Herz and Garrison,
1998) suggests that the Chinese understood the geometry
of mineral deposits and that the presence of cinnabar might
be used to locate some types of gold occurrences.
Far more is known about mercury in the 1500s and
later. For example, Agricola (1556) details mercury use
and retorting techniques and discusses the health effects
of breathing the fumes released during mercury retorting
in Europe in the 1500s. In the 1600s, mercury from the
Santa Barbara Mine, Huancavelica, Peru was essential to
Spanish Colonial silver processing at Potosí, Bolivia, and](https://image.slidesharecdn.com/2489511-250625053945-6e71613f/85/Mercury-In-The-Environment-Pattern-And-Process-1st-Edition-Michl-S-Bank-41-320.jpg)
![20 MERCURY CYCLING IN THE ENVIRONMENT
as a preservative to keep fine silks intact (Srinivasan and
Ranganathan, 2004).
Mercury was found in a ceremonial cup in an Egyptian
tomb that dates to 1600–1500 BCE (D’Itri and D’Itri, 1977).
Was the mercury placed in the tomb because it was silvery,
liquid, reflective, and needed in the afterlife? Or was mer-
cury intentionally used because its fumes, which volatize at
ambient temperatures, were known to be toxic and there-
fore, inhibited biologic activity and decay?
A kilogram of mercury, which may have been used for
amalgamation or gilding, was found near the Greek trading
site of al Mina, on the Syrian coast, which dates to 500 BCE
(Ramage and Craddock, 2000). Theophrastus (372–287 BCE)
was the first to describe refining and condensation of mer-
cury from cinnabar (Healy, 1978). He wrote the earliest work
on minerals and mining, “Peri Lithon” [On Stones], and
described the mining and processing of cinnabar in Iberia
and Colchis. However, the “Iberia” of Theophrastus’ time
was north of Turkey, the current republic of Georgia, and not
Spain. Colchis was to the south. Later, the cinnabar work-
shops were transferred to Rome because cinnabar had been
discovered in Spain (Caley and Richards, 1956).
Native mercury was associated with cinnabar occurrences
in Asia Minor at Ephesus, Turkey, and in Europe at Almaden,
Spain. Pliny the Elder (23–79 CE) described native mercury
droplets associated with silver and lead mines in Greece
(Healy, 1978). Pliny the Younger (61–113 CE) described a
method of recycling and purifying used mercury by squeez-
ing it through leather (D’Itri and D’Itri, 1977). At about the
same time, mercury was used to recycle gold from worn-out
golden embroideries by first ashing the material and then
treating the dampened ashes with mercury (Ramage and
Craddock, 2000).
In ancient China, cinnabar was also used for pigments
and the tomb of Emperor Ch’i-Huang-Ti, who died in
210 BCE, contained a large relief map of China in which the
oceans and rivers were represented by mercury (Schuette,
1931). The Chinese also believed that mercury or cinnabar
medications could prolong life, perhaps because of their
preservative qualities; however, several emperors died from
mercury poisoning in their attempts to attain immortality
(Leicester, 1961). Over 4000 years ago women in China drank
mercury as a contraceptive (Simon, 2004).
Mercury and gold were used as a part of the finishing
process on ceremonial swords in 12th century Japan. A
paste of mercury and gold was applied to decorate the pro-
tective collar (habaki) between the blade of the sword and
the user’s hand. The amalgam paste was then heated to
drive off the mercury. This process gilded the habaki with a
decorative gold accent (Kapp et al., 1987).
Whether or not mercury was used for amalgamation and
recovery of alluvial gold in the ancient world is controver-
sial. For example, Davies (1935), considered it unlikely that
mercury was used to recover gold, and scanning electron
microscope analyses of gold artifacts from Sardis did not
detect mercury (Ramage and Craddock, 2000). However, by
Worldwide, artisanal gold mining is the leading indus-
trial use of mercury, for example, in Colombia (Delgado,
2010), Brazil (Fialka, 2006), and Peru (Brooks et al., 2007).
Mercury is also widely used as an electrolyte to produce
chlorine and caustic soda from brine and is also used for
some batteries, children’s light-up toys and shoes, com-
pact and traditional fluorescent lamps, dental amalgam,
switches, and thermostats. Fever thermometers and some
medical measuring devices still use mercury; however, the
use of digital substitutes is increasing. The mercury used
in these products can be recycled, thereby, eliminating
releases that may potentially affect human health (Brooks
and Matos, 2005). Some skin-lightening creams and beauty
soaps may also contain mercury (al-Saleh and al-Doush,
1997). Information on global mercury production, use, and
releases since 1500 CE is provided by Hylander and Meili
(2003, 2005). Statistics on annual world mercury produc-
tion, domestic import sources and export destinations, and
prices are compiled in Brooks (2007).
Since 1927, mercury has been measured and priced by
the flask, a unique commercial unit that was introduced
at Almaden, Spain (Meyers, 1951). The flask itself is made
of welded steel, has a screw cap, and is about the size of a
2-L container. When filled, the flask weighs 34.5 kg, and
29 flasks of mercury are contained in a metric ton.
The Old World and Asia
Archaeological evidence indicates that mercury and cinna-
bar were known and widely used for industrial applications
before 1500 CE. In southwestern Turkey, in the Sizma dis-
trict, cinnabar was mined as early as 6300 BCE from what
may be the oldest known underground mine, a mercury
mine. A 14C date of 6280 BCE on cinnabar-painted skulls that
were excavated in the area suggests that the cinnabar may
have been sourced from occurrences in the Sizma district.
Near Ladik, also in the Sizma district, the 3 m2 hearth of a
mercury retort, carved into marble, was found. Cinnabar
would have been used for pigments or cosmetics and the
mercury would have been used for gilding or amalgama-
tion with alluvial gold found in the streams in the region.
Thus, it is very likely that cinnabar mining and mercury
production first originated in Turkey more than 8000 years
ago (Barnes and Bailey, 1972; Yildiz and Bailey, 1978).
Mercury was known in Spain before the Christian
Era, and the Moorish name of the mine “Almaden” and
the metal “azogue” (mainly in Latin America) are still in
use today. Near Valencia, Spain, well-preserved human
bones covered with powdered cinnabar were found in a
tomb that dates to 5000 BCE (Maravelaki-Kalaitzaki and
Kallithrakas-Kontos, 2003). Was the powdered cinnabar
used because of the life symbolism suggested by its blood-
red color? Or, perhaps, powdered cinnabar, now known to
be toxic (Sax, 1984), was selectively used because of its
toxicity and preservative qualities. These properties were
also understood in ancient India, where cinnabar was used](https://image.slidesharecdn.com/2489511-250625053945-6e71613f/85/Mercury-In-The-Environment-Pattern-And-Process-1st-Edition-Michl-S-Bank-42-320.jpg)
![INDUSTRIAL USE OF MERCURY IN THE ANCIENT WORLD 23
toxicity of mercury fumes and cinnabar powder by the
Romans, the Maya, and the Inca has largely been overrid-
den by mercury’s widespread usefulness in modern indus-
trial applications.
world. The selective use of powdered cinnabar as a preser-
vative in ancient funeral rituals to stop biologic decom-
position can only be inferred; however, now, the toxicity
of cinnabar is well established. Age-old awareness of the
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![24 MERCURY CYCLING IN THE ENVIRONMENT
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pp. 4, 29, 45, 55; Fig. 7.](https://image.slidesharecdn.com/2489511-250625053945-6e71613f/85/Mercury-In-The-Environment-Pattern-And-Process-1st-Edition-Michl-S-Bank-46-320.jpg)
![30 RESEARCH, MONITORING, AND ANALYSIS
particulate-bound Hg forms. Mercury also forms numer-
ous stable complexes with well-defined organic ligands
(e.g., ethylenediaminetetraacetic acid [EDTA]) and with
dissolved organic matter (DOM) to form organic mercury
compounds. Biologic transformations can convert Hg(II)
to gaseous elemental Hg and methylated Hg forms (see
Figure 3.1). In tissues, mercury can be present in both
inorganic and organo-Hg forms, with higher trophic level
species usually containing predominantly MMHg. In sed-
iments, mercury tends to adsorb preferentially to carbon-
based particles.
To perform a meaningful total Hg analysis, it is essen-
tial to perform a suitable preparation step to release the Hg
from whatever matrix or complexes in which it may reside.
Another factor that must be weighted in choosing a
suitable analytical method is the recognition that mer-
cury can exist in a wide variety of chemical forms that
may or may not be liberated for analysis by the procedures
adopted. Illustrated in Figure 3.2 are the various fractions
or pools of inorganic Hg(II) that can exist in natural water
systems. The common aqueous species of inorganic Hg(II)
in oxygenated freshwater are Hg(OH)2
0, and HgCl2
0. In
seawater, the dominant inorganic forms are the chlo-
ride species (HgCl4
2, HgCl3
1, etc). In suboxic to anoxic
waters, polysulfide species can dominant (e.g., HgS0) if
sulfide concentration levels exceed Hg concentration lev-
els. Hg(II) also strongly interacts with colloids and sus-
pended particles in aqueous systems to form colloidal or
table 3.2
Selected Methods for the Analysis of Mercury
Analyte Matrix Detector Reference or EPA method Typical MDL
Total Hg Water CVAAS EPA Method 245.1 5–10 ng/L
Total Hg Water CVAFS EPA Method 245.7 0.5–5 ng/L
Total Hg Water CVAFS EPA Method 1631 0.1–0.3 ng/L
Total Hg Water ICP-MS EPA Method 200.8 10 ng/L
Total Hg Water ICP-AES EPA Method 200.7 200 ng/L
Elemental Hg Water CVAFS EPA Method 1631 moda 0.1–0.3 ng/L
Reactive Hg Water CVAFS EPA Method 1631 modb 0.1–0.3 ng/L
MMHg Water CVAFS EPA Method 1630 (draft) 0.01–0.05 ng/L
Total Hg Sediment CVAAS EPA Method 245.5 5–10 ng/g
Total Hg Sediment CVAAS EPA Method 7471 10–50 ng/g
Total Hg Sediment DTDAAS EPA Method 7473 5–10 ng/g
Total Hg Sediment CVAFS EPA Method 1631 appendix 0.5–1 ng/g
MMHg Sediment CVAFS EPA Method 1630 modc 0.01–0.05 ng/g
MMHg Sediment GC-ICP-MS Bjorn et al. (2007)c 0.01–0.05 ng/g
Total Hg Tissue CV AAS EPA Method 245.6 5–10 ng/g
Total Hg Tissue DTDAAS EPA Method 7473 5–10 ng/g
Total Hg Tissue CVAFS EPA Method 1631 appendix 0.5–1 ng/g
Total Hg Blood ICP-MS Palmer et al. (2006) 0.17 g/L
Total Hg Blood FI-AAS Palmer et al. (2006) 0.6 g/L
MMHg Tissue CVAFS EPA Method 1630 modd 0.5–2 ng/g
AAS atomic absorption spectrometry; CVAAS cold-vapor atomic absorption spectrometry;
CVAFS cold-vapor atomic fluorescence spectrometry; FI Flow Injection; GC gas chromatography;
ICP-AES inductively coupled plasma atomic emission spectrometry; ICP-MS inductively coupled
plasma mass spectrometry; MDL Method Detection Limit; DTD Direct Thermal Decomposition.
a. Without oxidation or reduction.
b. Without oxidation.
c. Using extraction or distillation to isolate MMHg.
d. Using KOH/methanol digestion to release MMHg (Bloom 1989)](https://image.slidesharecdn.com/2489511-250625053945-6e71613f/85/Mercury-In-The-Environment-Pattern-And-Process-1st-Edition-Michl-S-Bank-52-320.jpg)
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- 6. Mercury in the Environment PATTERN AND PROCESS Edited by MICHAEL S. BANK UNIVERSITY OF CALIFORNIA PRESS Berkeley Los Angeles London
- 7. THE STEPHEN BECHTEL FUND IMPRINT IN ECOLOGY AND THE ENVIRONMENT The Stephen Bechtel Fund has established this imprint to promote understanding and conservation of our natural environment.
- 8. The publisher gratefully acknowledges the generous contribution to this book provided by the Stephen Bechtel Fund.
- 9. MERCURY IN THE ENVIRONMENT
- 11. Mercury in the Environment PATTERN AND PROCESS Edited by MICHAEL S. BANK UNIVERSITY OF CALIFORNIA PRESS Berkeley Los Angeles London
- 12. Library of Congress Cataloging-in-Publication Data Mercury in the environment : pattern and process / edited by Michael S. Bank. — 1st ed. p. cm. Includes bibliographical references and index. ISBN 978-0-520-27163-0 (hardback) 1. Mercury—Environmental aspects. 2. Mercury— Bioaccumulation. 3. Mercury—Toxicology. 4. Mercury— Health aspects. I. Bank, Michael S. TD196.M38M466 2012 363.738’4—dc23 2011052057 19 18 17 16 15 14 13 12 10 9 8 7 6 5 4 3 2 1 The paper used in this publication meets the minimum requirements of ANSI/NISO Z39.48-1992 (R 1997) (Permanence of Paper). Cover image: Miao settlements near Tianhe Pool Scenic Area, Guizhou Province, China, June 2009. Photo by Michael S. Bank. University of California Press, one of the most distinguished university presses in the United States, enriches lives around the world by advancing scholarship in the humanities, social sciences, and natural sciences. Its activities are supported by the UC Press Foundation and by philanthropic contributions from individuals and institutions. For more information, visit www.ucpress.edu. University of California Press Berkeley and Los Angeles, California University of California Press, Ltd. London, England © 2012 by The Regents of the University of California
- 13. C O N T E N T S CONTRIBUTORS vii FOREWORD ix INTRODUCTION xi ACKNOWLEDGMENTS xiii PART ONE Mercury Cycling in the Environment 1 Sources and Transport: A Global Issue / 3 PHIL SWARTZENDRUBER and DANIEL JAFFE 2 Industrial Use of Mercury in the Ancient World / 19 WILLIAM E. BROOKS PART TWO Methods for Research, Monitoring, and Analysis 3 Analytical Methods for Measuring Mercury in Water, Sediment, and Biota / 27 BRENDA K. LASORSA, GARY A. GILL, and MILENA HORVAT 4 Use of Stable Isotopes in Mercury Research / 55 HOLGER HINTELMANN 5 Atmospheric Chemistry, Modeling, and Biogeochemistry of Mercury / 73 NOELLE ECKLEY SELIN 6 A Framework for a Mercury Monitoring and Assessment Program: Synthesis and Future Research / 81 ROBERT P. MASON PART THREE Mercury in Terrestrial and Aquatic Environments 7 The Role of Soils in Storage and Cycling of Mercury / 99 ARIA AMIRBAHMAN and IVAN J. FERNANDEZ 8 Mercury Cycling in Terrestrial Watersheds / 119 JAMES B. SHANLEY and KEVIN BISHOP 9 Mercury Hotspots in Freshwater Ecosystems: Drivers, Processes, and Patterns / 143 CELIA Y. CHEN, CHARLES T. DRISCOLL, and NEIL C. KAMMAN 10 Mercury in the Marine Environment / 167 FRANK J. BLACK, CHRISTOPHER H. CONAWAY, and A. RUSSELL FLEGAL PART FOUR Toxicology, Risk Analysis, Humans, and Policy 11 Ecotoxicology of Mercury in Fish and Wildlife: Recent Advances / 223 ANTON M. SCHEUHAMMER, NILADRI BASU, DAVID C. EVERS, GARY H. HEINZ, MARK B. SANDHEINRICH, and MICHAEL S. BANK 12 Risk Evaluation of Mercury Pollution / 239 JOANNA BURGER and MICHAEL GOCHFELD 13 Mercury and Public Health: An Assessment of Human Exposure / 267 WENDY McKELVEY and EMILY OKEN 14 Mercury Exposure in Vulnerable Populations: Guidelines for Fish Consumption / 289 JOHN DELLINGER, MATTHEW DELLINGER, and JENNIFER S. YAUCK 15 Environmental Justice: The Mercury Connection / 301 JEROME NRIAGU, NILADRI BASU, and SIMONE CHARLES 16 Integrating Mercury Science and Environmental Policy: A State Perspective / 317 C. MARK SMITH INDEX 333
- 15. C O N T R I B U T O R S ARIA AMIRBAHMAN, University of Maine, Orono aria@umit.maine.edu MICHAEL S. BANK, Harvard Medical School, Boston, Massachusetts michael_bank@hms.harvard.edu NILADRI BASU, University of Michigan, Ann Arbor niladri@umich.edu FRANK J. BLACK, University of California, Santa Cruz fblack@westminstercollege.edu KEVIN BISHOP, Swedish University of Agricultural Science, Uppsala, Sweden kevin.bishop@slu.se WILLIAM E. BROOKS, United States Geological Survey, Reston, Virginia wbrooks@usgs.gov JOANNA BURGER, Rutgers University, Piscataway, New Jersey burger@biology.rutgers.edu CELIA Y. CHEN, Dartmouth College, Hanover, New Hampshire celia.y.chen@dartmouth.edu CHRISTOPHER H. CONAWAY, University of California, Santa Cruz kitconaway@hotmail.com JOHN DELLINGER, Concordia University, Mequon, Wisconsin john.dellinger@cuw.edu MATTHEW DELLINGER, University of Wisconsin, Milwaukee delling2@uwm.edu CHARLES T. DRISCOLL, Syracuse University, New York ctdrisco@syr.edu DAVID C. EVERS, Biodiversity Research Institute, Gorham, Maine david.evers@briloon.org A. RUSSELL FLEGAL, University of California, Santa Cruz flegal@ucsc.edu IVAN J. FERNANDEZ, University of Maine, Orono ivanjf@maine.edu SARAH GEROULD, United States Geological Survey, Reston, Virginia sgerould@usgs.gov GARY A. GILL, Pacific Northwest National Laboratory, Sequim, Washington gary.gill@pnl.gov SIMONE CHARLES, Georgia Southern University, Statesboro scharles@georgiasouthern.edu MICHAEL GOCHFELD, Robert Wood Johnson Medical School, Piscataway, New Jersey gochfeld@eohsi.rutgers.edu GARY H. HEINZ, United States Geological Survey, Beltsville, Maryland gheinz@usgs.gov HOLGER HINTELMANN, Trent University, Peterborough, Ontario hhintelmann@trentu.ca MILENA HORVAT, Jozef Stefan Institute, Ljubljana, Slovenia milena.horvat@ijs.si DANIEL JAFFE, University of Washington, Bothell djaffe@u.washington.edu NEIL C. KAMMAN, Vermont Department of Environmental Conservation, Waterbury neil.kamman@state.vt.us BRENDA K. LASORSA, Pacific Northwest National Laboratory, Sequim, Washington brenda.lasorsa@pnl.gov ROBERT P. MASON, University of Connecticut, Groton robert.mason@uconn.edu WENDY McKELVEY, New York City Department of Health and Mental Hygiene, New York wmckelve@health.nyc.gov vii
- 16. JEROME NRIAGU, University of Michigan, Ann Arbor jnriagu@umich.edu EMILY OKEN, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, Massachusetts emily_oken@hphc.org MARK B. SANDHEINRICH, University of Wisconsin, La Crosse sandhein.mark@uwlax.edu ANTON M. SCHEUHAMMER, Environmental Canada, Ottawa, Ontario tony.scheuhammer@ec.gc.ca NOELLE ECKLEY SELIN, Massachusetts Institute of Technology, Cambridge selin@mit.edu JAMES B. SHANLEY, United States Geological Survey, Montpelier, Vermont jshanley@usgs.gov C. MARK SMITH, Massachusetts Department of Environmental Protection, Boston c.mark.smith@state.ma.us PHIL SWARTZENDRUBER, Puget Sound Clean Air Agency, Seattle, Washington phils@pscleanair.org JENNIFER S. YAUCK, University of Wisconsin, Milwaukee jsy_ireland@hotmail.com viii CONTRIBUTORS
- 17. F O R E W O R D SARAH GEROULD I was a teenager when Life magazine published W. Eugene Smith’s famous pictures of Tomoko Uemura, her body rav- aged by deformities from Minamata disease. I remember poring over the pictures while sitting on our living room couch, wondering how such a thing could have happened and about how mercury could have caused these devastat- ing deformities. In 1972, the science of mercury in the envi- ronment was in its infancy. Although the neurologic symp- toms of Minamata disease were recognized well enough for specialists to identify mercury as the causative agent, the understanding of mercury’s environmental impacts and global dispersal would require several decades of research. The science of mercury has advanced considerably since those pictures were published. The global dispersion and speciation of mercury are now well recognized. The potential for methylmercury to cause neurologic deficits in segments of the world’s population that rely on a diet of piscivorous fish has been established (Mergler et al., 2007). Although the understanding of mercury’s implications for human health has advanced far enough to permit the development of criteria and consumption advisory levels for the protection of humans (United States Environmental Protection Agency, 2001, 2007a), field studies of effects in fish and fish-eating wildlife species continue to unveil new understanding of its impacts on these species. Scientists now recognize that mercury enters the environment through many sources, not just through point sources such as chloralkali plants and mining. Treatment technologies for removing mercury from air and water have advanced (United States Environmental Protection Agency 2007b). Monitoring has given us a wealth of data on concentra- tions in many environmental media. Our understanding of the environmental factors that control mercury spe- ciation have made significant advances (Munthe et al., 2007), although many important questions remain, such as the complexities of the relationship between mercury loading and the resulting concentrations in fish and the biogeochemical controls on the mercury methylation pro- cess (Munthe et al., 2007). Finally, the science of mercury sources and cycling is now mature enough to allow society to recognize and anticipate the effects of things such as fire and fluctuating reservoir levels (Grigal, 2002) as cofactors in controlling mercury cycling in the environment. Scientific understanding is not the only thing that has changed since W. Eugene Smith’s pictures were published. Regulatory agencies have recognized and reduced emissions from incinerators and other mercury sources in the United States (Lindberg et al., 2007). Though many sources of mer- cury have been regulated in recent years (United Nations Environment Programme, 2002), several new issues are now upon us. For example, the need for energy conserva- tion leads our society to use more compact fluorescent light bulbs, all of which contain mercury; and as U.S. sources are controlled, emissions from Asia, driven by increases in coal combustion and economic development, have sent more mercury into the air (Wong et al., 2006). Clouds of dust containing mercury are blown across the Atlantic and Pacific oceans and deposited onto distant landmasses (Garrison et al., 2003). Increases in atmospheric deposition of mercury in dust into parts of the arctic and subarctic environments (Pacyna and Keeler, 1995) are paralleled by increases in concentrations of mercury in wildlife (Braune, 2007). As the dynamics of global mercury sources and cycling continue to evolve, and science grows in its ability to doc- ument and explain mercury dynamics and effects, it is important to establish benchmarks of those changes and the progress toward understanding them. Michael Bank’s book provides a welcome update to the state of the art on mercury pollution. The contributors to the book are a strong list of experts who describe the latest findings rela- tive to the fate and effects of mercury in the environment. ix
- 18. x FOREWORD as climate change and landscape change. The book will be a reliable source of information for environmental managers, health professionals, scientists, and the educated public. It shows how far we’ve come in understanding this important issue since W. Eugene Smith published his pictures of Tomoko Uemura. The book summarizes mercury cycling and transport and dynamics in terrestrial, aquatic, and atmospheric environ- ments and exposure and effects in humans and wildlife. It includes information on historical uses and production of mercury. The book’s final section synthesizes issues affected by mercury or by which mercury is affected, such United Nations Environment Programme. “Chapter 7: current production and use of mercury.” in Global Mercury Assessment. pp. 117–134. Geneva, Switzerland: UNEP Chemicals, 2002. http://new.unep.org/gc/gc22/ Document/UNEP-GC22-INF3.pdf (accessed February 5, 2008). United States Environmental Protection Agency. “Methylmercury criteria document.” (EPA-823-R-01-001) January 2001, http://www.epa.gov/waterscience/criteria/ methylmercury/document.html (accessed February 5, 2008). United States Environmental Protection Agency. National Listing of Fish Advisories. Technical Fact Sheet: 2005/06 National Listing. Fact Sheet, EPA-823-F-07-003, July 2007a. http://www.epa.gov/waterscience/fish/advisories/2006/ tech.html (accessed February 5, 2008). United States Environmental Protection Agency. Office of Solid Waste and Emergency Response. Treatment Technologies for Mercury in Soil, Waste, and Water. EPA- 542-R-07-003. August 2007b http://www.epa.gov/tio/ download/remed/542r07003.pdf (accessed February 5, 2008). Wong, C.S., N.S. Duzgoren-Aydin, A. Aydin, and M.H. Wong. “Sources and trends of environmental mercury emissions in Asia.” Science of the Total Environment 368 (2006): 649–662. References Braune, B. “Temporal trends of organochlorines and mercury in seabird eggs from the Canadian Arctic.” 1975–2003. Environmental Pollution 148 (2007): 599–613. Garrison, V.H., E.A. Shinn, W.T. Foreman, D.W. Griffin, C.W. Holmes, C.A. Kellogg, M.S. Majewski, L.L. Richardson, K.B. Ritchie, and G.W. Smith. “African and Asian dust from desert soils to coral reefs.” Bioscience 53 (2003): 469–480. Grigal, D.F. “Inputs and outputs of mercury from terrestrial watersheds: A review.” Environmental Reviews 10 (2002): 1–39. Lindberg, S.,R. Bullock, R. Ebinghaus, D. Engstrom, X. Feng, W. Fitzgerald, N. Pirrone, E. Prestbo, and C. Seigneur. “A synthesis of progress and uncertainties in attributing the sources of mercury in deposition.” Ambio 36 (2007): 19–32. Mergler, D., H.A. Anderson, L.H.M. Chan, K.R. Mahaffey, M. Murray, M. Sakamoto, and A.H. Stern. “Methylmercury exposure and health effects in humans: A worldwide concern.” Ambio 36 (2007): 3–11. Munthe, J., R.A. Bodaly, B.A. Branfireun, C.T. Driscoll, C.C. Gilmour, R. Harris, M. Horvat, M. Lucotte, and O. Malm. “Recovery of mercury-contaminated fisheries.” Ambio 36 (2007): 33–44. Pacyna, J.M., and G.J. Keeler. “Sources of mercury in the Arctic.” Water, Air, & Soil Pollution 80 (1995): 621–632.
- 19. Mercury science is a rapidly growing interdisciplinary field and touches on nearly all academic and scientific disci- plines, including biogeochemistry, economics, sociology, public health, decision sciences, physics, global change, and mathematics. Only recently have scientists really begun to establish more holistic approaches to studying mercury pollution, including investigations that have fur- thered the integration of a multitiered approach, especially by using chemistry, biology, and human health sciences. The study of mercury pollution has contributed a variety of domestic and international policies related to the man- agement of this ubiquitous contaminant. The target audi- ence for this book is graduate and undergraduate students, natural resource managers, and technical scientists. The book focuses on integrating the diverse sciences involved in the process of mercury cycling in the environment from the atmosphere, through terrestrial and aquatic food webs, and in human populations to help the reader develop a more holistic perspective on this important environmental pollution topic. The original idea for the book was developed at a con- ference in 2004, after an associate of the University of California Press who had viewed my oral presentation sug- gested that I consider writing a book on mercury pollution. After some investigating, I soon realized that although there were strong volumes on mercury pollution, none of them had a solid focus on aspects related to human dimen- sions and new topics such as advances in mercury isotope chemistry, and that current public health summaries were not readily available in the literature. This book largely stems from my desire to impart knowledge from world- wide experts on their areas of expertise and to disseminate the most current scientific information available about mercury. The book has four parts: (I) mercury cycling in the environment: an introduction; (II) methods for research, I N T R O D U C T I O N Mercury on the Rise MICHAEL S. BANK monitoring, and analysis; (III) mercury in terrestrial and aquatic environments; and part (IV) toxicology, humans, policy, and risk analysis. Part I, “Mercury Cycling in the Environment: An Introduction,” serves as a basic introduction to the book. Chapter 1 focuses on sources, fate, and transport of mercury in the environment as a global problem and provides the reader with the critical background information on mer- cury pollution. Chapter 2 discusses historical and indus- trial uses of mercury in the environment, with a focus on ancient civilizations. The use of mercury by ancient civili- zations has not received much attention, and this chapter describes mercury as a utility of human societies. Part II, “Methods for Research, Monitoring, and Analysis,” is dedicated to summarizing and highlighting recent advances in the study methods used in mercury investigations. Recent advances in the analytical methods used to measure mercury in the environment are discussed in Chapter 3. Because these methods are advancing rather quickly in the field, this chapter will be an important source for students, chemists, and laboratory scientists. Chapter 4 focuses specifically on mercury isotope frac- tionation and the use and application of mercury isotopes in source apportionment research and in determining biogeochemical pathways of mercury in the environment. Chapter 5 is devoted to the atmospheric chemistry and modeling of mercury. This sole atmospheric deposition chapter discusses, in detail, the reactions, behavior, and chemical properties of mercury in the earth’s atmosphere and the role of scale and uncertainty assessments and their collective applications to monitoring, research, and policy. The chapter concludes by summarizing future challenges for mercury atmospheric deposition research. Chapter 6 focuses on indicators of environmental changes in mer- cury contamination in different ecosystem compartments and discusses the need for a national mercury monitoring xi
- 20. xii INTRODUCTION and ponds, reservoirs, wetlands, and rivers. The authors provide examples of mercury cycling and bioaccumulation by examining case studies from the Everglades, Adirondack mountain lakes, man-made reservoirs, large lakes such as Lake Michigan, and the Nyanza Superfund site on the Sudbury River in Massachusetts. Chapter 10 is a compre- hensive summary of mercury in the marine environment, with regard to human and environmental health concerns. In this chapter the authors discuss the source of mercury in marine ecosystems, methylation of mercury, and bioaccu- mulation and biomagnification in marine food webs. Part IV, “Toxicology, Risk Analysis, Humans, and Policy,” includes five chapters that discuss and summarize the recent advances in each of these important disciplines. Chapter 11 focuses on the ecotoxicology of mercury, pri- marily as methylmercury, in wildlife such as fish, amphib- ians, birds, and mammals. Chapters 12 through 15 are ded- icated to risk assessment, public health, and environmental justice. These chapters report on a variety of topics, includ- ing risk assessment models, human exposure routes of the different mercury species, and fish consumption patterns related to socioeconomic dynamics. Chapter 16 integrates many scientific aspects discussed throughout the book and summarizes mercury policy initiatives in the context of both environmental and human health. The field of mercury science is tremendous in scope and scale and I hope this book serves as a preliminary, introduc- tory step for students, researchers and scientists to develop a further interest and understanding of mercury pollution and cycling in the environment. network. This chapter discusses measurement approaches from the atmosphere to different wildlife indicator species that inhabit freshwater, terrestrial, and coastal ecosystems. The indicators identified in this chapter involve measure- ments made at several spatial and temporal scales and were selected to provide the best information to policymakers and other stakeholders and with regard to identifying the reasons and rates of change in mercury concentrations. Part III, “Mercury in Terrestrial and Aquatic Environ- ments,” includes four chapters that focus on mercury in soils, forested watersheds, freshwater ecosystems, and marine environments. Chapter 7 summarizes the current knowledge about mercury in soils, which is critical to our understanding of the accumulation and loss of mercury in the environment and outlines the relationships between kinetics, climate, vegetation, disturbances, soil chemistry, and mercury speciation. Chapter 8 goes beyond soils and discusses mercury in forested watersheds. In this chapter, the authors review and synthesize information about mer- cury in terrestrial landscapes and describe how total mer- cury and methylmercury move through forested catch- ments. The authors also discuss, in detail, the role and effects of disturbance (forest harvesting, urbanization, etc.) on total mercury and methylmercury fluxes and their sen- sitivity to changes in mercury emission rates, land-use prac- tices, and climate. Chapter 9 deals with mercury in freshwa- ter ecosystems. In this chapter, the authors describe biotic and abiotic mechanisms that govern mercury methylation, bioaccumulation, and trophic transfer in a wide array of aquatic food webs and ecosystems, including natural lakes
- 21. Jennifer Wachtl, Art Lage, and John Spengler for their support, guidance, and encouragement throughout vari- ous stages of the project. I am grateful to all of the indi- vidual chapter reviewers, and I thank the two anonymous reviewers for their comments on the entire volume manu- script. I am grateful to Harvard Medical School and HSPH, Department of Environmental Health and their excep- tional administrative staff, especially Renee Costa, Joan Arnold, Tracy Mark, Rose West, and Linda Fox. I thank Blake Edgar, Hannah Love, Lynn Meinhardt, Kate Marshall, and Kate Hoffman at the University of California Press in Berkeley, for their patience and guidance throughout all phases of the book’s development. I am also grateful to project manager Michael Bohrer-Clancy of Macmillan Publishing Solutions. Although I am the sole editor of this volume, I could not have edited it without support from a variety of sources. I received support during the course of editing this book from Harvard University, the Massachusetts Department of Envi- ronmental Protection, the National Science Foundation, the National Oceanic and Atmospheric Administration, the United States Department of Agriculture, Harvard School of Public Health (HSPH), the United States Geological Survey, HSPH-National Institute of Environmental Health Sciences Center for Environmental Health (NIEHS grant number ES000002), the New York Department of Environmental Conservation, the International Union for Conservation of Nature-Amphibian Specialist Program, and the Akira Yama- guchi Endowment at Harvard School of Public Health. In addition to all the contributors, I am grateful to Anh- Thu Vo, Jeff Crocker, Colin Davies, Philippe Grandjean, A C K N O W L E D G M E N T S xiii
- 23. PART ONE MERCURY CYCLING IN THE ENVIRONMENT
- 25. 3 CHAPTER 1 Sources and Transport A Global Issue PHIL SWARTZENDRUBER and DANIEL JAFFE ANTHROPOGENIC SOURCES OF MERCURY IN THE AIR Chemical Speciation REEMISSION OF PREVIOUSLY DEPOSITED MERCURY MERCURY EMISSIONS: SUMMARY, UNCERTAINTY, AND VALIDATION FROM RELEASE TO GLOBAL TRANSPORT Aqueous Transport Ocean Settling and Transport Atmospheric Transport Continental Export and Long-Range Transport Global Transport SUMMARY CHEMICAL FORMS OF MERCURY IN WATER AND AIR THE CHANGING GLOBAL CYCLE OF MERCURY Sediments and Ice Cores as Archives of Geochemical Cycles The Preindustrial Cycle Evidence of Recent Changes in Deposition of Mercury The Modern Mercury Cycle SOURCES OF MERCURY IN WATER Atmospheric Wet and Dry Deposition Industrial Point Sources Mining Runoff Methylated Species NATURAL PROCESSES THAT EMIT MERCURY INTO THE AIR Chemical Forms of Mercury in Water and Air The Roman deity, Mercury, was the god of trade, commerce, thievery, and messengers. His reputation as a cunning and swift messenger led to the modern adjective, mercurial, meaning labile, volatile, and erratic. Many contemporary scientists who study mercury would emphatically agree that its behavior in the environment and in the labora- tory often seems erratic and mysterious. Indeed, it was only relatively recently that we became aware of the global nature of mercury contamination, partly because of the difficulty in detecting it at the extremely low concentra- tions that are typical in air and water. Thus, we encounter an apparent paradox fitting of Mercury’s reputation; why are there toxic levels of mercury in fish in remote regions throughout the globe despite water and air concentrations that are very low? The answer is a complex process of emis- sion, transport, deposition, and accumulation up through the food chain. All of the major steps in this process have been clearly identified, although a number of the specific mechanisms remain poorly understood. In this chapter we will give an overview of the chemical forms present in the air and water, their sources, and how they are transported. The chemical symbol for mercury, Hg, is derived from the Latin name, hydragyrum, which means silver water. Elemental mercury is found in the Earth’s crust in only a limited number of regions in the world. Mercury is more abundant in mineral form, with cinnabar (HgS) being the most prevalent. Several of the less abundant minerals include calomel, Livingstonite, and Tiemannite. Mercury is predominantly found in deposits formed by hydrothermal systems, which are most common at convergent tectonic margins. It also tends to be enriched in some base-metal ores and present with other chalcophilic (having a sulfur affinity) elements (Kesler, 1994). The elemental form of mercury (Hg0) has had a great number of uses historically, including barometers, thermometers, electrical switches, fluorescent light bulbs, and ballast for submarines. Elemental mercury has a unique combination of properties that seem to make it ideal for these applications. Hg0 is the only abundant metal that is liquid at room temperature. It has a melting
- 26. 4 MERCURY CYCLING IN THE ENVIRONMENT soil and ocean reservoirs, and therefore soil and ocean emissions, include a component that is natural, plus a portion resulting from human activities at a prior time. Research has shown that most natural samples exhibit measurable mass-dependent isotope fractionation and some exhibit mass-independent fractionation. Although this subfield of mercury research is in its infancy, it shows promise in providing new insights into the sources and history of ambient mercury (Bergquist and Blum, 2007). CHEMICAL SPECIES OF MERCURY Hg0 is elemental mercury. Hg0 has an anomalously high vapor pressure (Brown et al., 2008) for a heavy metal. It is slightly water-soluble (~50 µg/L at 20°C) (Clever et al., 1985) and has a high Henry’s law coefficient (729 at 20°C) (Schroeder and Munthe, 1998). In the natural environment, it can exist in the gaseous or liquid state. Gaseous element mercury (GEM), is the dominant form in the atmosphere. Most natural waters are nearly saturated, or are supersaturated with respect to atmospheric Hg0 (Fitzgerald et al., 2007). Hg(II) or divalent mercury. Inorganic and organic divalent mercury compounds exist in gaseous, dissolved, and solid states. Their toxicity, solubility, vapor pressure, and reactivity vary greatly. Hg(II) is much more prevalent in waters than in the atmosphere. Methylated mercury compounds (below) are of particular interest because of their role in the biologic cycling of Hg and accordingly make up >95% of the mercury in fish (Chen et al., 2008). DMHg is dimethylmercury, (CH3)2Hg. DMHg is significantly more toxic than Hg0 on a milligrams point of –39°C and a boiling temperature of 357°C. It also has a rather high vapor pressure despite having a density 13 times greater than water and slightly greater than lead. This anomalous behavior is caused by weak inter-atomic bonding, which is due to the nucleus having a tight hold on its valence electrons. Hg0 is also relatively insoluble in water (49 µg/L or 4.4 ppt at 20°C which is 4 to 6 orders of magnitude smaller than the solubility of the predominant Hg compounds) and will readily avoid liquids. So, it is often described as preferring to be in the gas phase. Mercury can also be found in two ionic forms, oxidation states ⫹1 and ⫹2, which are more prevalent in water than in the atmo- sphere (Schroeder and Munthe, 1998). A number of the mercury compounds that occur in the environment have not been directly identified. Rather, sev- eral different fractions of mercury have been defined based on how they are collected (e.g., on a filter) and how elemen- tal mercury can be released from them (e.g., heating the filter to 800°C). These distinctions, called “operationally defined fractions,” are then used in place of specific compounds. The properties of the different fractions (e.g., solubility, volatility, etc.) are used in modeling the fate of mercury. As instrumen- tation and techniques have developed, the definitions of the fractions have evolved, and, not surprisingly, there is still some controversy as to the names and definitions of some of the fractions. A simplified chart of the forms of mercury that occur in water and air is shown in Figure 1.1. The major operationally defined fractions are indicated with color. One of the challenges of studying the cycling of mer- cury is that because it is an element, it is never destroyed, but it can be recycled through the environment. In specific terms, mercury that is deposited to soils, lakes, wetlands, or oceans may later be re-released to the atmosphere. So, FIGURE 1.1 A simplified diagram of the major chemical forms of mercury found in water and air. See the section on “Chemical Forms of Mercury in Water and Air” for a description of the forms. DGHg ⫽ dissolved gaseous mercury; DMHg ⫽ dimethylmercury; HgR ⫽ reac- tive mercury; MMHg ⫽ monomethylmercury; PHg ⫽ particulate-bound mercury; RGM ⫽ reactive gaseous mercury; TAM ⫽ total airborne mercury; THg ⫽ total mercury. Waterborne Airborne Reactive Hg (HgR) is DGHg plus dissolved Hg(II). Note that in contrast to air, reactive mercury includes Hg 0 . Dissolved Gaseous Hg (DGHg) is the sum of DMHg and Hg 0 . Total Airborne Mercury (TAM) is often defined as the sum of three species, Hg0 , Hg(II) (reactive gaseous mercury or RGM), and PHg. Hg0 Hg(II) PHg Total Hg (THg) is the sum of all waterborne species. DMHg Hg(II) Hg0 MMHg PHg
- 27. SOURCES AND TRANSPORT: A GLOBAL ISSUE 5 on larger particles would be excluded from the reported concentration. The amount of mercury extracted from the particles can be dependent on the technique used. Waterborne particulate mercury is generally determined by filtration, addition of BrCl, reduction with SnCl2, and purging with a clean, inert gas. Measuring airborne PHg also requires capturing particles on a filter. The filters can be analyzed in the aqueous phase using the previously described technique. Or, the mercury on particles can be thermally reduced/desorbed, and quantified as GEM (Landis et al., 2002). The Changing Global Cycle of Mercury Sediments and Ice Cores as Archives of Geochemical Cycles Lake sediment cores and glacial ice cores have been used as historical records of preindustrial and anthropogenic deposition. Trace metal and hydrocarbon concentrations in cores have been shown to accurately reflect the impact of industrialization on air concentrations and increased deposition of pollutants to the earth (e.g., Wong et al., 1984) and oceans (Véron et al., 1987). Mercury has also been studied in ice cores and lake sediments, and similar increases in deposition are seen across a wide range of geologic and hydrologic environments (e.g., Swain et al., 1992; Schuster et al., 2002). These records are powerful evidence of the recent anthropogenic influence on the global Hg cycle. The Preindustrial Cycle A diagram of the simplified global mercury cycle is shown in Figure 1.2 (after Mason and Sheu, 2002). Preindustrial values are shown in parentheses below the modern val- ues. The glacial and sediment records have shown that in the millennium before industrialization, mercury and other metals had a relatively steady deposition flux, with an occasional perturbation due to volcanic activity (e.g., Schuster et al., 2002). This implies that the net flux of mer- cury coming into the atmosphere approximately equaled the net flux deposited to the land and oceans. There is sub- stantial evasion from the ocean and land, but it is nearly balanced by deposition. There is also local recycling of mercury over the ocean surface (not shown) that makes no contribution to the net evasion or deposition (Strode et al., 2007). Rivers also make a small contribution to the open ocean (~1% of ocean reservoir), but this is omitted from the figure for the sake of simplicity. In the preindus- trial cycle, the annual flux into and out of the atmosphere (~2–4000 tons/yr) is similar to the total airborne bur- den, suggesting a lifetime for atmospheric Hg of approxi- mately 1 year (Mason and Sheu, 2002; Selin et al., 2008). In the oceans, the total burden is more than a factor of per kilogram of body weight ingestion basis (due to more efficient absorption in the gut). It is believed to be present in the atmosphere in only negligible concentrations, but it is thought to be ubiquitous in the deeper ocean (Mason et al., 1998). MMHg is monomethylmercury, CH3Hg+. MMHg is significantly more toxic than Hg0 on a milligrams per kilogram of body weight ingestion basis (due to more efficient absorption in the gut) and readily bio- accumulates up the food chain (National Research Council, 2000). MMHg has not been reliably detected in the open oceans apart from the Equatorial Pacific Ocean (Fitzgerald et al., 2007). OPERATIONALLY DEFINED FORMS OF MERCURY DGHg is dissolved gaseous Hg. It is a fraction of mercury measured in water that is defined by its ability to be volatilized only by purging with a clean, inert gas. It includes DMHg (Fitzgerald et al., 2007). HgR is reactive Hg dissolved in water. It is defined based on its ability to be volatilized after reduction with SnCl2, and purging with a clean, inert gas (Fitzgerald et al., 2007). Hg(II) has also been used as an operationally defined fraction of dissolved Hg. It is determined by subtracting mercury that is readily volatilized (DGHg) from reactive Hg (HgR) (Mason et al., 1998). It has been used as a measure of bio-available mercury, but is known to not be universally appropriate (Fitzgerald et al., 2007). Hg-Col is colloidal mercury. It is mercury associated with colloidal matter that can be trapped on an ultrafine membrane after filtration of larger particulate matter. Colloidal mercury is generally considered to be larger than 1000 Da (molecular weight) but smaller than 0.1–0.5 µm (Guentzel et al., 1996). RGM or reactive gaseous mercury, refers to Hg that can be captured on a KCl surface (Landis et al., 2002). RGM is believed to consist primarily of gaseous Hg(II) compounds. It is regarded as the fraction of airborne Hg that is readily deposited to the surface via wet or dry deposition. The exact chemical form of RGM is not known, but likely candidates include HgO (Hall, 1995), HgCl2 (Landis et al., 2002), and HgBr2 (Holmes et al., 2009). In many reports, RGM and gaseous Hg(II) are used interchangeably, but it is important to recognize that RGM is an operation definition whereas Hg(II) is a chemical definition. PHg, or particulate-bound mercury, refers to mercury that is extracted from particles, either airborne or waterborne. The observed PHg concentration can be dependent on the size of particles that are collected; for example, most airborne PHg measurements include only particles ⬍2.5 µm (aerodynamic diameter), so mercury
- 28. 6 MERCURY CYCLING IN THE ENVIRONMENT As an example, Figure 1.3 shows lake sediment profiles of Hg enrichment from four lakes in the Western United States. Here, enrichment is the Hg enhancement, relative to another element that is assumed to be purely lithospheric in origin, titanium. These data are from a study of Hg and persistent organic pollutants from eight National Parks in the western United States and Alaska that receive only atmospheric input (Landers et al., 2008). Enrichment is relative to titanium concentrations in the sediment cores and is defined by: Percent Sediment Enrichment ⫽ (Mx兾Tix) ⫺ (Mb兾Tib) __ (Mb兾Tib) ⫻ 100 where Hgx ⫽ mercury concentration (ng/g) at interval depth x Tix ⫽ titanium concentration (ng/g) at interval depth x Hgb ⫽ mercury concentration (ng/g) at interval closest to year 1870 Tib ⫽ titanium concentration (ng/g) at interval closest to year 1870 These lake sediments show a clear enhancement in mercury deposition from the preindustrial era to the pres- ent, consistent with other studies (e.g., Swain et al., 1992; Schuster et al., 2002). Increases in the deposition rate, aver- aging about threefold, are widely observed, although there are significant variations between sites. Individual lakes and cores can vary because of local geography, geology, and local emissions. These factors are not well understood and limit our overall understanding of the Hg cycle. For example, once deposited, Hg can be sequestered by organic carbon. Thus, a change in organic carbon in the air or lake can change the fraction of Hg that is permanently cap- tured. Nonetheless, the increased atmospheric deposition to the catchment, from both regional and global sources, is required to explain the enhancements in Hg deposition in the lake sediment cores. (Swain et al., 1992; Fitzgerald et al., 1998; Schuster et al., 2002; Landers et al., 2008). Observations of wet and dry deposition and large-scale modeling of the global Hg cycle indicate that input from the atmosphere is the primary cause of the increased accu- mulation in the sediments. There is, nonetheless, still sig- nificant uncertainty in some of the mechanisms involved (e.g., Calvert and Lindberg 2005; Lin et al., 2006; Lindberg et al., 2007). The fraction of the mercury deposition that can be attributed to local (or regional) sources versus the global background is an area of continued research. A num- ber of modeling studies have apportioned local and regional deposition to various sources, including anthropogenic (local and global), natural, and recycled. For example, in the United States, Seigneur et al., (2004) estimate that 30% of total deposition is from North American anthropogenic sources, 40% is due to anthropogenic sources outside North America, and 33% is from natural sources. Selin et al., (2008) 100 greater than the annual flux, indicating a much lon- ger lifetime for Hg. Therefore, for any given change in the global cycle (e.g., anthropogenic emissions), we can expect that the atmosphere will respond much more rapidly than the ocean. Further, since the mixing and circulation of the atmosphere occurs much more rapidly than that of the ocean, we can expect that changes in the atmospheric bur- den will be seen much more rapidly throughout the globe than changes in the ocean. The net lifetime of mercury against long-term burial (i.e. lifetime in the atmosphere, surface ocean, and land surface system) is on the order of 1000 years (Selin et al., 2008). Evidence of Recent Changes in Deposition of Mercury Significant advances in mercury detection and sampling have occurred in the past 20 years. These advances have allowed for reliable determination of current and his- torical levels of Hg deposited in sediments and ice cores. Despite some initial contradictory reports, there is now a good consistency between studies of deposition from a large number of locations in North America, South America, New Zealand, and Europe. These studies show a compelling pattern of increasing deposition to lake sedi- ments and glacial ice (Swain et al., 1992; Fitzgerald et al., 1998; Lamborg et al., 2002; Landers et al., 2008) and a generally consistent pattern in peat cores (Biester et al., 2002, 2007). Atmosphere Surface Ocean Deep Reservoirs Land 1900 (950) 1600 (810) 1500 (900) 2600 (850) 200 (90) 90 (90) 2400 1500 900 (local) Industry FIGURE 1.2 A simplified global geochemical mercury cycle. All values are tons per year. Preindustrial values are given in parenthe- ses below the modern values. The inner, dashed circle indicates the perturbation of industrial activities that significantly increased the extraction of mercury from deep reservoirs. This results in signifi- cantly greater local deposition and also increased input to the global atmospheric pool, which increases global deposition. Upward arrows from the land and ocean are net evasion and downward arrows are wet and dry deposition. (Source: Adapted from Mason and Sheu, 2002.)
- 29. SOURCES AND TRANSPORT: A GLOBAL ISSUE 7 found that 68% of the deposition is anthropogenic, with 31% coming from outside North America. As primary anthropogenic sources emit some mercury in forms that can be deposited locally (RGM and PHg) (Pacyna and Pacyna, 2002), the issue of source attribution encompasses multiple spatial scales (Seigneur et al., 2004; Selin et al., 2007). The Modern Mercury Cycle The modern, industrial cycle of mercury differs from the preindustrial cycle (Figure 1.2) because of the extraction and mobilization of Hg from deep reservoirs. (Deep res- ervoirs are defined as reservoirs that are physically below the surface ocean and land surface which contain a large mass of mercury relative to the mass that cycles through the land, air, and water, on an annual basis). Anthropogenic activities have greatly increased the mobilization of Hg (e.g., coal combustion and mining) from deep reservoirs. This enhanced Hg extraction is thought to have increased the total atmospheric burden of Hg by about a factor of 3, which has resulted in a nearly threefold increase in deposition to the land and ocean. But, it should be noted that the observa- tional record of Hg in the atmosphere is relatively short, so no clear pattern of change has been found (Ebinghaus et al., 2009). Increased concentrations in the surface ocean and land surface have accordingly increased emissions back to the atmosphere. Thus, the total amount of mercury cycling through the land surface, surface oceans, and atmosphere, has increased significantly (Selin et al., 2008; Sunderland et al., 2009). The burden of total mercury in the deep oceans has also increased, but by a much smaller factor. The smaller increase in deep ocean concentrations is largely a result of the much greater reservoir of Hg and slower mixing and turnover times. This produces a lag in uptake on the order of decades to centuries in the surface waters and deep ocean, respectively (Sunderland and Mason, 2007). Year % Enrichment 2000 1975 1950 1925 1900 1850 0 50 100 150 200 250 Cd Hg Ni Cd Hg Ni Cd Hg Ni Cd Hg Ni Oldman Lake, Glacier NP Matcharak Lake, GOTA-NPP –50 –25 0 25 50 75 100 % Enrichment % Enrichment 1875 Year % Enrichment 2000 1975 1950 1925 1900 1850 0 50 100 150 200 PJ Lake, Olympic NP 1875 Mills Lake, RNP 0 100 200 300 400 FIGURE 1.3 Four examples of the enrichment in Hg deposition found in lake cores in the Western United States. Oldman Lake is in Glacier National Park, Montana; Matcharak Lake is in Gates of the Arctic National Park and Preserve, Alaska; PJ Lake is in Olympic National Park, Washington; and Mills Lake is in Rocky National Park, Colorado. (Source: Landers et al., 2008).
- 30. 8 MERCURY CYCLING IN THE ENVIRONMENT fish, which were a staple of the local diet. In the following years, more than 100 people died and more than 1000 were permanently disabled from the resulting methylmercury poisoning, which consequently bears the name, Minimata Disease (Clarkson, 1997). It is also important to note that, by definition, the increased deposition (of RGM and particulate-bound Hg) to oceans and lakes throughout the globe as compared with preindustrial times is ultimately attributable to anthropo- genic activities. Though the input occurs after transport through the atmosphere, it is nonetheless of anthropogenic origin. Mining Runoff An additional important source of mercury to aquatic systems is runoff or leaching resulting from mining activities. Large-scale mercury mines often produce large quantities of tailings or leave mining passages open after operations cease (e.g., Sulfur Bank Mercury Mine, California [Engle et al., 2007]; Almadén, Spain [Gray et al., 2004]; Idrija, Slovenia [Hines et al., 2006]). Early gold and silver mining also produced large quantities of Hg-enriched tailings because Hg was added to crushed ore in order to amalgamate and extract the gold and silver (e.g., Bonzongo et al., 1996). The wastes, along with the open mine passages, allow rain and groundwater to leach and mobilize mercury. Even smaller-scale mining activities, in particular artisanal mining practiced in China, Indonesia, South America, and Africa (reviewed by Veiga et al., 2006) produce significant amounts of waste matter that is enriched in mercury. This is often dumped into streams or lakes, or otherwise allowed to leach in an uncontrolled manner. Methylated Species Perhaps the most crucial process in the global cycling of mercury, at least from the standpoint of toxicity, is the con- centration and accumulation of MMHg or DMHg up the food chain (called “bio-accumulation”). Most of the DMHg and MMHg that is bio-accumulated is produced in situ in natural waters or near the sediment–water interface. The production of MMHg and DMHg from dissolved Hg(II) (methylation) occurs primarily in sulfate-reducing bacteria in anoxic environments and has been hypothesized to be a cellular detoxification mechanism. A limited number of other methylation mechanisms have been proposed, but bacteria appear to be the largest producers in lakes and wetlands (Rudd, 1995; Fitzgerald et al., 2007). Little DMHg and MMHg is found in the surface waters of the open ocean. Higher concentrations of DMHg can be found below the mixed layer of the open ocean and periph- eral seas, while MMHg has been unambiguously detected only in coastal zones, peripheral seas, and the Equatorial Pacific Ocean (Fitzgerald et al., 2007). Sources of Mercury in Water Atmospheric Wet and Dry Deposition The largest and most important source of mercury in water is wet and dry deposition from the atmosphere. This includes both a natural and anthropogenic component. Globally, about 1% of the total oceanic burden is deposited and emit- ted each year (Mason and Sheu, 2002; Sunderland and Mason, 2007). Most of the mercury deposited to oceans in precipitation is either bound to particles or is dissolved in an ionic state, Hg(II). Over the oceans, the overwhelming por- tion that is dry deposited is RGM, which has been produced near the water surface from photochemically driven oxida- tion by halogens (Laurier et al., 2003; Sprovieri et al., 2003; Laurier and Mason, 2007; Holmes et al., 2009). A portion (~10%) of the RGM that is deposited to the ocean is reduced to elemental mercury in the surface waters, either directly by sunlight, or through biologic activity (Fitzgerald et al., 2007; Strode et al., 2007). This tends to make the surface waters supersaturated with respect to dissolved elemental mercury (Schroeder and Munthe, 1998). Therefore, (gaseous) elemen- tal mercury is generally evading from the ocean surface. Lakes and wetlands are more variable in their interaction with GEM. Some studies have reported supersaturations in surface waters with net evasion (Poissant et al., 2000, 2004), and others have observed slow net deposition or near equi- librium with the air (Zhang and Lindberg, 2000) or diurnal cycles (Marsik et al., 2005). Mercury that is bound to particles and bound to soluble organic complexes can also be incorporated into the hydro- logic cycle as a part of runoff after rain or flooding events and through the movement of subsurface pore water. Subsurface geothermal and hydrothermal vents are also sources of mercury in the ocean, although the magnitude of these inputs is believed to be negligible as compared with the total oceanic burden. Subsurface vents may, none- theless, be important in enhancing the concentrations in ambient waters and sediments near the vent site (Stoffers et al., 1999; King et al., 2006; Lamborg et al., 2006). Some mercury is also thought to enter (or perhaps reenter) the hydrologic cycle from diagenetic reactions, which are phys- ical, chemical, or biologic changes that occur as sediment (settled particulate matter that contains mercury) is depos- ited, compressed, and transformed to rock. Industrial Point Sources Industrial waste is an important source of Hg to some watersheds. The most prominent example of anthropo- genic input of mercury to aquatic system occurred in Mini- mata, Japan, in the early 1950s. Throughout this period, the Chisso Corporation dumped more than 20 tons of mercury that had been used as a catalyst in the production of acet- aldehyde, into Minamata Bay. The mercury contaminated the sediments, water, and ecosystem and ultimately the
- 31. SOURCES AND TRANSPORT: A GLOBAL ISSUE 9 into surface waters locally through photochemical pro- cessing. They estimated that the net flux out of the marine boundary layer is only about 1500 tons/yr. Using a three- dimensional global model that was constrained to observed mercury concentrations in the ocean, Strode et al. (2007) calculated a significantly larger net flux of 2800 tons/yr. A large fraction of this, however, was considered to be reemis- sion of previously deposited mercury. For forest fires, most of the mercury released probably came from recent deposition to the soil and vegetation, and so is partly reemission of previous anthropogenic and natural emissions (see the section on “Mercury Emissions: Summary, Uncertainty, and Validation,” below). Weiss-Penzias et al. (2007) estimated global emissions of mercury from for- est fires of 670 ⫾ 330 tons/yr based on observations of the Hg:CO ratio in 10 biomass burning plumes. Wiedinmeyer and Friedli (2007) used a similar approach to estimate U.S. emissions of mercury from wildfires, and arrived at 44 tons/ yr with an uncertainty of 50%. In summary, natural emis- sions of Hg are an important component of the global cycle, but there are large uncertainties with regard to our estimates of these emissions. Anthropogenic Sources of Mercury in the Air Emissions inventories of anthropogenic sources of mercury have been compiled for most developed countries. These are based on direct stack tests to determine the amount of mercury being emitted for a particular facility. The emission per unit of production is termed an “emission factor.” The emission factor from one facility is often used to estimate the emissions from another facility that has not had a direct stack test. This, of course, assumes that both factories operate similarly, with identical fuel and emission controls. While the emissions for large facilities can be relatively well known, emissions from smaller facilities are often excluded from emission inventories, and this can result in a significant error in the total emissions. The most important example is Chinese emissions from coal com- bustion and metals smelting. Because of less centralized consumption of coal (Wong et al., 2006) and a lack of data regarding activity levels and emissions factors from smaller operations and remote regions (Wu et al., 2006), there is considerable uncertainty (⫾44%) about the total estimate (Streets et al., 2005). Based on emissions inventories, anthropogenic sources are believed to emit approximately 2200–3400 tons/yr of mercury to the atmosphere. While there are many different source types, the largest sources, in order of importance, are coal combustion, gold production, nonferrous metal smelting, cement production, caustic soda manufacturing, and waste incineration (Pacyna et al., 2006; Selin et al., 2008). Coal combustion is the largest source globally, and is responsible for about 1400 tons/yr, which is nearly two thirds of the global anthropogenic total (Pacyna et al., 2006). In most first-world countries, coal combustion is carried Natural Processes That Emit Mercury into the Air A number of natural processes emit mercury to the atmosphere. The origins of the mercury emitted from these processes may be purely natural, or they may be a mix of natural and anthropogenic (reemissions) (Gustin et al., 2008). Volcanoes, geothermal vents, and naturally enriched soils release mercury that originated in deep reservoirs, so can be considered purely natural emissions. Land, emissions, forest fires, and ocean emissions are mixed sources because a significant fraction of their Hg burden was previously deposited, which includes some anthropogenic mercury (Selin et al., 2008). Quantifying natural sources of mercury in the air is difficult because of the large range of source types, natural variability, concomitance with anthropogenic mercury, and the global scale of the problem. Nonetheless, it is critical to quantify these sources, as without an understanding of natural sources it is difficult to understand the scale of anthropogenic influence. Ideally, we would like to quantify preindustrial mercury emissions as a reference point for present-day emissions. Since we obviously cannot go back in time and make direct observations, the estimation of preindustrial emissions must be done indirectly through models and sediment records. Based on a small number of measurements, estimated mercury releases from volcanoes are 100–800 tons/yr (Varekamp and Buseck, 1986; Nriagu and Becker 2003; Pyle and Mather 2003). The only known estimate of global geothermal emissions (60 tons/year) is from Varekamp and Buseck (1986) based on average Hg content in hot springs and a global estimate of convective heat flux. The emission of Hg from naturally enriched soils and exposed mineral deposits has been studied on small scales. A very limited number of global estimates have been made by scaling up the local emissions, but these are highly uncertain (Gustin et al., 2008). An early estimate of 500 tons/yr for global mercury emissions from soils was made by Lindqvist, et al. (1991). The flux of mercury from soil is a complicated function of soil concentration, light, moisture, temperature, and other factors (e.g. Gustin, et al., 1999; Ericksen, et al., 2006; Xin, et al., 2007). In one study, rainfall was found to increase the flux of mercury from desert soils by approximately an order of magni- tude (Lindberg, et al., 1999), thus showing the complex- ity of quantifying soil flux. Based on recent observations and an understanding of soil mercury concentrations in geologically enriched regions across the United States, Ericksen et al., (2006) estimated a release of 100 tons/yr from soils in the contiguous United States. Several models of the global mercury cycle have used a global land flux of 500 tons/yr (Seigneur, et al., 2004; Selin et al., 2007). Oceanic emissions are believed to be the largest compo- nent of all natural emissions. Mason and Sheu (2002) esti- mated that oceanic emissions of mercury are 2600 tons/yr; however, a significant fraction of this is “recycled: back
- 32. 10 MERCURY CYCLING IN THE ENVIRONMENT (1997) estimate of atmospheric emissions of Hg in South America by gold mining (179 tons/yr) is nearly twice the total Hg emissions from all sources in South America esti- mated by Pacyna et al. (2006). But, it should be noted that the Pacyna et al. (2006) inventory does not quantify Hg emissions from South American gold mining, nor does it attempt to quantify Hg emissions from illegal gold mining activities. In addition, the Pacyna study used an Hg emis- sion factor of 0.5 g of Hg emitted/g of gold produced, whereas Lacerda used a factor of 1.5. Thus, while emissions of Hg from gold mining are clearly a substantial source for the global atmosphere, there is significant uncertainty in the actual values. In developed countries, emissions of mercury have decreased in the past two decades, partly because of some direct emission controls, but mostly as a side benefit to controls on other pollutants (US EPA, 1997; Pacyna et al., 2006). Emissions in Europe have decreased nearly 50%, partly because of controls on other pollutants, but also because of political and economic changes that led to plant closures and reductions in coal use. China is the world’s largest emitter of mercury, with emissions of ~700 tons/yr (Pacyna et al., 2006; Wu et al., 2006). This is approximately one third of the global anthro- pogenic total. The next five top-emitting countries, in order, are South Africa, India, Japan, Australia, and the United States. Chinese emissions are rapidly increasing because of strong growth in the economic output and the increas- ing utilization of coal (e.g., Kim and Kim, 2000; Tan et al., 2000; Wu et al., 2006). It should also be noted that Chinese Hg emissions are expected to continue to increase for some time because of China’s large coal reserves (Zhang et al., 2002) that have moderate to high Hg content (Zheng et al., 2007). Coal combustion and metal smelting are the two largest sources in China, although the larger of these is still somewhat uncertain. Metal smelting is the largest source of mercury in China in the Wu et al. (2006) and Streets et al. (2005) inventories, whereas coal combustion is the largest source in the Pacyna et al. (2006) inventory. While coal consumption is increasing rapidly in China, there is also greater utilization of ESPs for particulate removal, which can partially offset this increase (Wu et al., 2006). According to Wu et al. (2006), Chinese mercury emissions increased by 2.9% per year from 1995 to 2003. For the United States, the anthropogenic emissions were recently quantified as part of the Clean Air Mercury Rule (CAMR), for the years 1990, 1996, and 1999. The mercury emissions were found to have decreased from 245 metric tons in 1990 to 124 tons in 1999. The drop was largely due to controls on medical and municipal incineration, as well as controls on other pollutants, such as SO2 and aerosols, which had a side benefit of also reducing mercury. As of 1999, the largest single category for mercury emissions in the United States is coal combustion, which is responsible for 43% of total U.S. emissions. (see http://www.epa.gov/ camr/charts.htm). out almost entirely in the industrial and power generation sectors, whereas in developing countries, notably China, a significant fraction of coal combustion also occurs in the residential sector (Wu et al., 2006). Emissions from coal combustion can vary substantially from facility to facility. The mercury emission factor from coal combustion depends mainly on two factors: 1. Concentration of mercury in the coal 2. The degree of emission controls The concentration of mercury in coal can vary by more than two orders of magnitude, from 0.01 to 1.5 g of Hg/ton of coal (Pacyna et al., 2006). In addition, there are also large variations in control technologies. For example, the simplest particulate control technology, a cyclone, has almost no ability to capture mercury. A more complicated technique that is widely used, electrostatic precipitators (ESP), can remove approximately 30% of mercury in the stack emissions. Flue-gas desulfurization with an ESP can remove up to 74% of the mercury (Streets et al., 2005; Wu et al., 2006, Pacyna et al., 2006). Thus, emission factors (e.g., kilograms of Hg emitted per ton of coal consumed) vary greatly from plant to plant and country to country. Coal combustion can produce Hg as GEM, RGM, or PHg. Gold production is the second largest source of mercury globally. These emissions are primarily the result of large-scale mining activities of gold-rich ores (which are almost always enriched in mercury) and small-scale, artisanal mining, which extracts gold by amalgamating it with mercury. Since gold and mercury are often colocated in the same deposit, these regions generally have natu- rally high emissions of mercury in the form of GEM (Engle et al., 2001; Coolbaugh et al., 2002). Mining activities, including digging, pulverizing, and roasting the ore, will significantly increase the mercury emissions. While the use of mercury to amalgamate and concentrate gold is now illegal in most parts of the world, this method is still used, especially in remote, third-world locations. Emissions from the disturbed deposits and wastes can continue for years, and thus current emissions are a result of both current and past practices. Some historically contaminated mining sites can accumulate substantial water and soil mercury concen- trations and result in significant atmospheric emissions, for example, the Carson River Superfund site in Nevada (Gustin et al., 1996; Leonard et al., 1998). In Venezuela, Garcia-Sanchez et al. (2006) studied several sites polluted from past mining activities. In some gold processing shops, they found GEM concentrations of 50 to ⬎100 µg/m3, which is more than 20,000 times greater than background concentrations. Lacerda (1997) published a summary of Hg emissions from past and current gold mining. In this estimate, 460 tons/yr are released to the environment globally, an d65% of this is released to the atmosphere. Of the total atmospheric emis- sions, nearly 60% is released in South America. Lacerda’s
- 33. SOURCES AND TRANSPORT: A GLOBAL ISSUE 11 Mercury emissions that result from low-temperature vol- atilization (e.g., evaporation of mercury from concentrated mining waste) are emitted nearly 100% as GEM. Sources that involve high-temperature combustion (e.g., coal com- bustion or metal smelting) are more likely to contain some mercury in other forms. Depending on the coal type and combustion conditions, RGM and PHg could be as much as 46% of the mercury emissions (Seigneur et al., 2001). Globally, anthropogenic mercury emissions are believed to be 53% GEM, 37% RGM, and 10% PHg (Pacyna et al., 2006). For the United States, emissions are reported as 50% GEM, 46% RGM, and 4% PHg. For China, the Hg emissions are reported to be 57% GEM, 33% RGM, and 10% PHg. As mentioned previously, RGM and PHg will primarily deposit locally, so the large emissions in China have a significant contribution to deposition within Asia (Jaffe and Strode, 2008). Unfortunately, the values given above have signifi- cant uncertainty, and thus limit our ability to model the relative importance of global versus regional sources at any particular location. Reemission of Previously Deposited Mercury Evidence for reemission of previously deposited mercury has been shown in a number of studies. For example, Landis and Keeler (2002) estimated the evasion of mercury from Lake Michigan to be 38% of the annual wet and dry deposition flux. A study using mercury isotopes in a Canadian lake showed conclusively that recently deposited mercury could be reemitted to the atmosphere (Southworth, et al., 2007). Nearly all reemissions of mercury are in the form of Hg0, regardless of how the mercury entered the system. With respect to reemission, the key question is how much of the emissions from any one source is natural and how much is due to anthropogenic activities that may have taken place months to years ago? This question is impor- tant in that it directs us to identify the natural component of the global mercury cycle against which human-caused changes can be understood (e.g., the anthropogenic contri- bution to Hg in fish). However, quantifying the total frac- tion of current emissions that is natural versus anthropo- genic is a challenging task. Probably the ice-core records and the lake-sediment cores, which document historic deposition trends, are the best evidence for large-scale changes in global mercury cycling (see the section on “The Changing Global Cycle of Mercury,” above). Mercury Emissions: Summary, Uncertainty, and Validation Current estimates are that emissions of mercury are 6000–11,000 tons/yr, with the sources divided approxi- mately equally between natural, direct anthropogenic, and reemissions from past activities. Table 1.1 gives a sum- mary of the direct anthropogenic emissions from several The CAMR was finalized in March 2005 to reduce emissions of mercury from coal power plants. This rule (along with the Clean Air Interstate Rule), would reduce mer- cury emissions from coal power plants in the United States from 48 tons/yr to 15 tons/yr by the year 2018. However, the rule proposes to use a “cap and trade” method, whereby not all power plants need to reduce their emissions uni- formly. Under a cap-and-trade system, one plant can reduce their emissions more than is required and sell the result- ing “credits” to a plant that did not reduce their emissions as much, or at all. This could result in “hotspots,” where mercury deposition remains high and unaffected by the national emission reductions (e.g., Evers et al., 2007). The situation is further complicated by several lawsuits regard- ing the way the United States Environmental Protection Agency (EPA) regulated mercury via the CAMR. Prior to 2005, mercury was listed as a Hazardous Air Pollutant (HAP) in section 112 of the U.S. Clean Air Act (see http:// www.epa.gov/oar/caa/caa112.txt). This would require the “maximum achievable” control of a listed pollutant on a plant-by-plant basis and would be inconsistent with a cap- and-trade approach. As part of its March 2005 decision, mercury was de-listed as a hazardous air pollutant and the CAMR regulations were put into place by the EPA. As a result of this action by the EPA, the CAMR rules were challenged in court by a broad coalition of states, Native American groups, and an array of health and environmen- tal organizations. On February 8, 2008, the U.S. Court of Appeals for the District of Columbia overturned the EPA’s CAMR. Thus, at the time of this writing (mid-2009), the final form for any rules on mercury emissions from coal power plants in the United States are in question. Chemical Speciation While most natural mercury sources emit Hg0 (GEM), this is not the case for anthropogenic emissions, which consist of a mix of particle-bound mercury (PHg), Hg(II) compounds (or RGM), and Hg0. The relative proportions of these is specific to each facility and source type. The chemical speciation is important for the simple reason that the different forms have vastly different lifetimes and thus vastly different impacts on the local environment. Hg0 has a long enough lifetime in the atmosphere (about 1 year) that it mixes throughout the globe before reentering the terrestrial cycle, whereas PHg and RGM are removed from the atmosphere in a matter of hours to days and are thus much more important for local and regional bioaccumula- tion. In short, GEM is largely a global problem, whereas PHg and RGM are of regional concern. A further com- plication is that in some industries, stack tests are often only required to measure total mercury, without regard to the chemical form. For understanding and modeling the deposition and environmental influence, the chemical form can easily be more important than the total amount being emitted.
- 34. 12 MERCURY CYCLING IN THE ENVIRONMENT fairly convincing that the total outflow of mercury from Asia is significantly larger than that reported by the anthro- pogenic inventory alone. This is due to a combination of underestimates in the industrial sources, combined with land emissions, both natural and reemissions. In the most complete examination of anthropogenic emissions, Selin et al. (2008) suggested that all categories of Hg emissions were significantly larger than previously assumed, with anthropogenic emissions of 3400 tons/yr, natural emissions of 3200 tons/yr, and reemissions of 4100 tons/yr. However, as stated previously, all of these estimates have significant uncertainty. From Release to Global Transport The transport and deposition of mercury from the atmo- sphere is a crucial pathway for contamination in remote ecosystems. Hydrologic transport also plays a role in redis- tributing mercury, but because of the slower movement and mixing of the oceans, this plays only a small role in the enhancements of mercury in remote ecosystems. On con- tinents, the transport of mercury in surface and subsurface waters is primarily important in redistributing high mer- cury levels near contaminated sites. Aqueous Transport RIVERINE Rivers play an important role in the local transport of mercury from contaminated sites, but have a less significant role in the global cycle. Mason et al. (2002) and Sunderland and Mason (2007) estimate that about 1–2% of the total sources to the ocean come from inputs from rivers, with dissolved and particle-bound Hg being the largest fractions. Sunderland and Mason (2007) note that a large fraction of the particulate mercury carried by rivers sources Note that an estimate by Selin et al, (2008) has a much higher emission total for anthropogenic sources (3400 tons/yr). Emission inventories should be considered as a “work in progress.” By this we mean that source tests often omit both large and small facilities, emissions are constantly changing, factories are omitted, new information is uncov- ered, and chemical processes and fuels change. This is not meant as a criticism of emission inventories, only as a realistic assessment of their limitations and uncertainties. Emission inventories need validation against atmospheric observations to examine consistency. Observations downstream of a major source region can give quantitative information on the emission. For exam- ple Jaffe et al. (2005) used observations on the island of Okinawa to quantify the emissions and outflow of mercury from Asia. They found that a much larger source of Hg was required to reconcile the atmospheric observations with the existing emission inventory. Combining observations with a transport model can improve the estimate of emis- sions. Two studies that examined the same Okinawa data along with data from the Mt. Bachelor Observatory in cen- tral Oregon and using the GEOS-CHEM model (Selin et al., 2007; Strode et al., 2008) also confirmed a much larger Asian source of Hg than had been previously assumed. Strode et al. (2008) compared the Hg:CO ratio in GEOS- Chem to observations at Okinawa and at Mt. Bachelor in central Oregon, and found that an Asian source of 1260– 1470 tons/yr of Hg0 was consistent with the observations. Models can also be run in “inverse” mode, whereby the emission inventories are derived directly from the best fit with observations. Using this approach with aircraft obser- vations from the western Pacific, Pan et al. (2007) also found that Hg0 emissions were significantly greater from China than the current emission inventory, consistent with the earlier studies mentioned above. These studies are table 1.1 Direct Anthropogenic Emissions of Mercury (tons/yr) Source China Asia United States Global Global Coal combustion 257 879 54a NR 1422 Gold mining 45 47 6b 300 248 Nonferrous smelting 320 88 NR NR 149 Cement production 35 90 NR NR 140 Total all sources 696 1180 126 NR 2190 Year 2003 2000 1998/1999 NR 2000 Reference Wu et al., 2006 Pacyna et al., 2006 Seigneur et al., 2001 Lacerda, 1997 Pacyna et al., 2006 NR ⫽ not reported. a. Includes all fossil fuel stationary sources, but the total is dominated by facilities burning coal. b. All mining sources.
- 35. SOURCES AND TRANSPORT: A GLOBAL ISSUE 13 estimate that coastal benthic MMHg production rates and diffusional efflux are sufficient that they are likely a major source to nearby ecosystems and potentially the open ocean. Atmospheric Transport DISPERSION OF POINT AND AREA SOURCE PLUMES The majority of direct anthropogenic mercury emissions are from point sources such as coal-fired power plants, municipal waste incinerators, metal refineries, and chlor- alkali plants. The dispersion of these types of plumes has been widely studied, and a range of tools exist to describe the fate of chemicals in those plumes (e.g., Mossio et al., 2001). GEM emitted from these sources is largely unreac- tive and has been suggested to be useful tracer of sources (Friedli et al., 2004; Jaffe et al., 2005). RGM and PHg have much different fates. RGM is rapidly deposited to particles and surfaces, and can be sequestered by cloud and rain drops (Schroeder and Munthe, 1998). Particulate mercury can also settle out of the atmosphere or become incorpo- rated into rain and cloud drops. Depending on the ambient conditions and the chemistry of the emitted plume, some of the RGM may be reduced to GEM (Lohman et al., 2006). Thus, if an airmass remains in contact with the surface, a large fraction of the RGM and PHg will be lost to the surface within hours to days of emission. Continental Export and Long-Range Transport Large, polluted airmasses can be exported from their source region, and then transported and dispersed over thousands of kilometers in the jet stream through their interaction with a midlatitude cyclone. Because the lifetime of GEM in the atmosphere is about 1 year (Selin et al., 2007), in some cases plumes have been observed for 7–10 days or more after emission (Jaffe et al., 2005; Slemr et al., 2006; Ebinghaus et al., 2007; Weiss-Penzias et al., 2007; Swartzendruber et al., 2008). In these studies, the mercury source region was identified through a combination of trajectory and synop- tic analysis, and the calculation of enhancement ratios of copollutants. The enhancement ratios reflect the emission ratio (under certain assumptions) and, because of a signifi- cant difference in emission ratios between the major emit- ters (Jaffe et al., 2005; Weiss-Penzias et al., 2007), can sug- gest a source type. The suggested source type and backward air-parcel trajectories can then be compared with emissions maps. This approach has been successful in identifying intercontinental transport of Hg from sources in East Asia, Europe, and Africa. Modeling studies have confirmed the long-range transport of Hg seen in observations (e.g., Selin et al., 2007; Jaffe and Strode, 2008; Strode et al., 2008). Global Transport Once polluted airmasses are lofted into the jet stream, they can circle the northern hemisphere in as little as 7–10 days and will is deposited in estuarine regions and oceanic shelves and does not reach the open ocean. Also, because wetlands can be strong producers of MMHg, the outflow from wetlands can be significant sources to downstream water bodies (St. Louis et al., 1996). One study of fate and transport in a boreal wetland found that over the course of several months, significant fractions of a newly deposited isotope (202Hg) were converted to MMHg and were transported below the water table and toward a neighboring lake via groundwater (Branfireun et al., 2005). Ocean Settling and Transport The world’s oceans play an important role in transporting and redistributing heat throughout the globe, but they do not play as prominent a role for mercury. This is primarily due to the much shorter intrahemispheric mixing time of the atmosphere (~10–20 days [Jacob, 1999]) as compared to the oceans (10s to 1000s of years [Sunderland and Mason, 2007]). Also, the short lifetime of Hg in the surface oceans against reemission (~0.6 year [Selin et al., 2008]) means that the surface ocean and atmosphere are in steady state on an annual time scale. Thus, the atmosphere will act to damp local perturbations from the surface ocean. Noteworthy oceanic transport processes include up/down- welling, interhemispheric transport, particle settling, and transport of MMHg from coastal sediments. Mason et al. (1994) estimated that upwelling of thermo- cline waters in the equatorial Pacific is similar to the net atmospheric input to the surface, and in some places it may be greater. This, along with observations of elevated mercury in subsurface waters (Mason and Fitzgerald, 1993; Mason and Sullivan, 1999; Horvat et al., 2003) suggests that mercury- enriched water masses may sink from the surface and be transported as a record of historical deposition. Nonetheless, because of the relatively slow exchange rate of the world’s oceans, the fluxes in and out of intermediate and deep reser- voirs are a very small fraction of their overall burden. Oceanic transport also likely contributes to interhemi- spheric transport. The lifetime of mercury in deep ocean compartments is much longer, 10s to 1000s of years (Sunderland and Mason, 2007) than surface reservoirs and would allow for interhemispheric transport. The impact of this mercury on atmospheric concentrations and deposi- tion to land, however, would depend on the deep waters reaching the surface. The settling of particulate mercury, from the surface to deep waters and the ocean floor, is an important component in the oceanic cycle, particularly in the North Atlantic. In the surface waters, carbon-rich biomass or waste matter produced by phytoplankton or zooplankton sequesters mercury and falls to the interme- diate and deep ocean. It is believed that about 50% of the sinking mercury is buried on the ocean floor and is lost to deep reservoirs (Sunderland and Mason, 2007). The transport of MMHg from coastal sediments is also an important form of oceanic transport. Fitzgerald et al. (2007)
- 36. 14 MERCURY CYCLING IN THE ENVIRONMENT within the contiguous United States, but that there is considerable spatial variability in this value (9–81%). This is due to the significant emissions of RGM and PHg in the Eastern United States, which makes a significant contribu- tion to deposition regionally. On the other hand, GEM will be intercontinentally transported in 7–10 days, and within 1–2 months it will be distributed throughout the hemisphere. Slowly, GEM is oxi- dized to RGM, which is more readily removed by wet and dry deposits. While the GEM oxidation mechanism remains uncertain (Lindberg et al., 2007), its impact is felt in a vari- ety of environments (Swartzendruber et al., 2006; Steffen et al., 2008; Weiss-Penzias et al., 2009). This is a key process that makes Hg a global pollutant. Figure 1.4 shows the per- cent deposition that can be attributed to emissions from the major industrial regions: Asia, United States, Europe, and the sum of all anthropogenic sources. Note that this includes only the deposition due to recent anthropogenic sources and does not include anthropogenic mercury that has been previously deposited and reemitted. Each source region contributes to global Hg deposition in proportion to its total emissions (see Table 1.1). What is clear from Figure 1.4 is that Hg is a global pol- lutant that knows no boundaries. To substantially reduce deposition and bioaccumulation of Hg in any part of the world will require reductions in the global emissions. generally be dispersed in the midlatitude “pollution belt” in 1–2 weeks (Jacob, 1999). During transport, the airmasses tends to be stretched into long filaments and begin mixing into to the global background. Although the pollution and plumes can be swiftly transported over long distances at higher alti- tudes, their impact on the surface obviously depends upon them descending to the surface, which can be a slow process. There is also transport and exchange of Hg between the hemispheres, although this is considerably slower, and requires on the order of 1 year for exchange to occur. The slower interhemispheric exchange along with the greater anthropogenic emissions in the northern hemisphere creates a very useful property, an interhemispheric gradient, which is a powerful constraint on the sources and global lifetime of Hg. The interhemispheric gradient provides clear evidence for increasing anthropogenic emissions, especially in the northern hemisphere (e.g., Slemr and Langer, 1992; Lamborg et al., 2002, Strode et al., 2007). Industrial emissions of RGM and PHg are relatively short- lived and deposit to surfaces within a day or two of being emitted. In contrast, most GEM will be exported from the source region and continue to mix into the hemispheric background. Thus, the chemical form of Hg emissions are key to understanding the impacts. In their modeling study, Seigneur et al. (2004) show that North American industrial sources contribute between 25 and 32% to total deposition 90°N 60°N 30°N 0° 30°S 60°S 90°S 180° 120°W 60°W 0° 60°E 120°E 180° Asian anthropogenic contribution 90°N 60°N 30°N 0° 30°S 60°S 90°S 180° 120°W 60°W 0° 60°E 120°E 180° North American anthropogenic contribution 0 90°N 60°N 30°N 0° 30°S 60°S 90°S 180° 120°W 60°W 0° 60°E 120°E 180° Global anthropogenic contribution 20 40 60 80% 90°N 60°N 30°N 0° 30°S 60°S 90°S 180° 120°W 60°W 0° 60°E 120°E 180° European anthropogenic contribution 0 20 40 60 80% 0 20 40 60 80% 0 20 40 60 80% FIGURE 1.4 GEOS-Chem global chemical transport model estimates of annual average fraction of deposition that is due to anthropogenic emissions from Asia, North America, Europe, and all anthropogenic sources for 2004. Note that this is simply the direct deposition that does not include mercury that has been previously deposited to, and reemitted from the ocean and land. (Figures and modeling work provided by S. Strode.)
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- 41. 19 CHAPTER 2 Industrial Use of Mercury in the Ancient World WILLIAM E. BROOKS soon replaced mercury brought across the Atlantic from the centuries-old Almaden Mine in Spain (Putman, 1972). The slaves and indigenous workers at Huancavelica were exposed to cinnabar powder from mining, mercury fumes from mining and retorting, dust that contained silica and arsenic compounds, cold, high altitude, carbon monoxide, cave-ins, and poor ventilation; therefore, Huancavelica came to be known as the “mina de la muerte” [mine of death] (Brown, 2001). In Europe in the 1800s, mercury was widely used for gilding domes and interiors of cathedrals, domes of government buildings, and religious figures and also for mirror backing. Mercuric nitrate was widely used for mak- ing hats, and the term “mad hatter” was associated with those who were affected by the fumes released during the process. The term “vermeil” was also used in the 19th cen- tury; it referred to a sterling silver product, for example, a wine cooler, with all surfaces coated with a minimum of 10 karat gold that was of a minimum thickness of 2.5 µm; however, this process was banned because the artisans became blind as a result of exposure to mercury. Tableware made by this metallurgical process is kept on display in the Vermeil Room in the White House, Washington, DC. Along with polished copper, brass, silver, and obsidian, the reflec- tive qualities and movement of native mercury made it intriguing as a scrying, or fortune-telling, mirror. Mercury has also been used as a mirror to reflect light for transmit- ted light microscopes. Powdered cinnabar, or vermillion, was widely used as an artist’s pigment in Europe from the 1300s until the 1900s (Windhaven Guild, 2004) and is still available from art suppliers (Iconofile, 2010). Mercury compounds were used to inhibit mold in some household paints; however, because of its toxicity, mercury is no longer used for this application. THE OLD WORLD AND ASIA THE NEW WORLD CONCLUSION Mercury and cinnabar, the common ore of mercury, were known and used by ancient people in Africa, Asia, Central America, Europe, Mexico, and South America. Archaeolo- gists have shown that cinnabar was mined and mercury was produced more than 8000 years ago in Turkey. Cinnabar was a multiuse pigment in many parts of the ancient world, and mercury was used for gilding or placer gold amalgama- tion. Mercury was the earliest known treatment for syphilis, and its use is described in the Canon of Medicine by the Persian physician Ibn Sina (Avicenna) in 1025 CE. Even though cinnabar and mercury are found world- wide, the most well-known occurrences include those in Almaden, Spain; California; Huancavelica, Peru; Idrija, Slovenia; the Sizma district, Turkey; and the Yangtze region, China. The mineral name “cinnabar” may have been derived from Sinop, also called Cinab, a Black Sea port that was an export center for cinnabar and mercury (also called “ruddle”) produced in ancient Turkey (Barnes and Bailey, 1972). An undated Chinese saying “where there is cinnabar above, yellow gold will be found below” (Herz and Garrison, 1998) suggests that the Chinese understood the geometry of mineral deposits and that the presence of cinnabar might be used to locate some types of gold occurrences. Far more is known about mercury in the 1500s and later. For example, Agricola (1556) details mercury use and retorting techniques and discusses the health effects of breathing the fumes released during mercury retorting in Europe in the 1500s. In the 1600s, mercury from the Santa Barbara Mine, Huancavelica, Peru was essential to Spanish Colonial silver processing at Potosí, Bolivia, and
- 42. 20 MERCURY CYCLING IN THE ENVIRONMENT as a preservative to keep fine silks intact (Srinivasan and Ranganathan, 2004). Mercury was found in a ceremonial cup in an Egyptian tomb that dates to 1600–1500 BCE (D’Itri and D’Itri, 1977). Was the mercury placed in the tomb because it was silvery, liquid, reflective, and needed in the afterlife? Or was mer- cury intentionally used because its fumes, which volatize at ambient temperatures, were known to be toxic and there- fore, inhibited biologic activity and decay? A kilogram of mercury, which may have been used for amalgamation or gilding, was found near the Greek trading site of al Mina, on the Syrian coast, which dates to 500 BCE (Ramage and Craddock, 2000). Theophrastus (372–287 BCE) was the first to describe refining and condensation of mer- cury from cinnabar (Healy, 1978). He wrote the earliest work on minerals and mining, “Peri Lithon” [On Stones], and described the mining and processing of cinnabar in Iberia and Colchis. However, the “Iberia” of Theophrastus’ time was north of Turkey, the current republic of Georgia, and not Spain. Colchis was to the south. Later, the cinnabar work- shops were transferred to Rome because cinnabar had been discovered in Spain (Caley and Richards, 1956). Native mercury was associated with cinnabar occurrences in Asia Minor at Ephesus, Turkey, and in Europe at Almaden, Spain. Pliny the Elder (23–79 CE) described native mercury droplets associated with silver and lead mines in Greece (Healy, 1978). Pliny the Younger (61–113 CE) described a method of recycling and purifying used mercury by squeez- ing it through leather (D’Itri and D’Itri, 1977). At about the same time, mercury was used to recycle gold from worn-out golden embroideries by first ashing the material and then treating the dampened ashes with mercury (Ramage and Craddock, 2000). In ancient China, cinnabar was also used for pigments and the tomb of Emperor Ch’i-Huang-Ti, who died in 210 BCE, contained a large relief map of China in which the oceans and rivers were represented by mercury (Schuette, 1931). The Chinese also believed that mercury or cinnabar medications could prolong life, perhaps because of their preservative qualities; however, several emperors died from mercury poisoning in their attempts to attain immortality (Leicester, 1961). Over 4000 years ago women in China drank mercury as a contraceptive (Simon, 2004). Mercury and gold were used as a part of the finishing process on ceremonial swords in 12th century Japan. A paste of mercury and gold was applied to decorate the pro- tective collar (habaki) between the blade of the sword and the user’s hand. The amalgam paste was then heated to drive off the mercury. This process gilded the habaki with a decorative gold accent (Kapp et al., 1987). Whether or not mercury was used for amalgamation and recovery of alluvial gold in the ancient world is controver- sial. For example, Davies (1935), considered it unlikely that mercury was used to recover gold, and scanning electron microscope analyses of gold artifacts from Sardis did not detect mercury (Ramage and Craddock, 2000). However, by Worldwide, artisanal gold mining is the leading indus- trial use of mercury, for example, in Colombia (Delgado, 2010), Brazil (Fialka, 2006), and Peru (Brooks et al., 2007). Mercury is also widely used as an electrolyte to produce chlorine and caustic soda from brine and is also used for some batteries, children’s light-up toys and shoes, com- pact and traditional fluorescent lamps, dental amalgam, switches, and thermostats. Fever thermometers and some medical measuring devices still use mercury; however, the use of digital substitutes is increasing. The mercury used in these products can be recycled, thereby, eliminating releases that may potentially affect human health (Brooks and Matos, 2005). Some skin-lightening creams and beauty soaps may also contain mercury (al-Saleh and al-Doush, 1997). Information on global mercury production, use, and releases since 1500 CE is provided by Hylander and Meili (2003, 2005). Statistics on annual world mercury produc- tion, domestic import sources and export destinations, and prices are compiled in Brooks (2007). Since 1927, mercury has been measured and priced by the flask, a unique commercial unit that was introduced at Almaden, Spain (Meyers, 1951). The flask itself is made of welded steel, has a screw cap, and is about the size of a 2-L container. When filled, the flask weighs 34.5 kg, and 29 flasks of mercury are contained in a metric ton. The Old World and Asia Archaeological evidence indicates that mercury and cinna- bar were known and widely used for industrial applications before 1500 CE. In southwestern Turkey, in the Sizma dis- trict, cinnabar was mined as early as 6300 BCE from what may be the oldest known underground mine, a mercury mine. A 14C date of 6280 BCE on cinnabar-painted skulls that were excavated in the area suggests that the cinnabar may have been sourced from occurrences in the Sizma district. Near Ladik, also in the Sizma district, the 3 m2 hearth of a mercury retort, carved into marble, was found. Cinnabar would have been used for pigments or cosmetics and the mercury would have been used for gilding or amalgama- tion with alluvial gold found in the streams in the region. Thus, it is very likely that cinnabar mining and mercury production first originated in Turkey more than 8000 years ago (Barnes and Bailey, 1972; Yildiz and Bailey, 1978). Mercury was known in Spain before the Christian Era, and the Moorish name of the mine “Almaden” and the metal “azogue” (mainly in Latin America) are still in use today. Near Valencia, Spain, well-preserved human bones covered with powdered cinnabar were found in a tomb that dates to 5000 BCE (Maravelaki-Kalaitzaki and Kallithrakas-Kontos, 2003). Was the powdered cinnabar used because of the life symbolism suggested by its blood- red color? Or, perhaps, powdered cinnabar, now known to be toxic (Sax, 1984), was selectively used because of its toxicity and preservative qualities. These properties were also understood in ancient India, where cinnabar was used
- 43. INDUSTRIAL USE OF MERCURY IN THE ANCIENT WORLD 21 related to Pacal, in a nearby tomb and known as the “Red Queen” were covered in powdered cinnabar (Hawkes and Hammond, 1997; Miller, 2001). Cinnabar was one of several pigments used to decorate incense burners used for funeral rituals at Palenque (Vazquez and Velazquez, 1996). A photograph available on the Internet shows the cinnabar- covered remains of a Mayan woman at Copan, Honduras (250–900 CE) (Garrett, 2007). In Central America, mercury occurrences are known in Guatemala, Honduras, and El Salvador, but the only occurrences for which production has been reported are in Honduras (Roberts and Irving, 1957). Of these, only the La Cañada Mine, Departamento Tegucigalpa, Honduras, was worked during the Spanish Colonial period. The cinnabar occurrences in Central America were known and exploited from early prehistory as sources of the intense red pigment that was used for painting ceramics and other artifacts (Karen Bruhns, Ph.D., professor, San Francisco State University, written communication, October 9, 2007). In the mud in Lake Amatitlan, Guatemala, marine archaeologists found two containers with mercury that date to the Early Classic Period (300–600 CE) (Mata Amado, 2002). Jade and shell fragments were found floating on a tiny, approximately 130-g pool of mercury in a closed container in a Mayan tomb that dates to 900–1000 CE in Belize (Pendergast, 1982). There are a number of gold, silver, or lead–zinc occur- rences in Central America and South America that, geo- logically, may have had minor mercury or cinnabar in the upper parts of the mineral deposits. For example, bedrock occurrences of cinnabar were exploited in the 1900s and later, in the 1950s, at Witlage Creek in eastern Suriname (Capps et al., 2004). Approximately 20 mercury occurrences are known in Peru (Petersen, 1970); however, the occurrences in Huancavelica are the most well-known (Yates et al., 1951; McKee et al., 1986) and the most likely source of mercury and cinnabar used in ancient Peru. There are also cinnabar occurrences near Azoguines and Cuenca, Ecuador, which are not as well known as those at Huancavelica, that were also exploited (Truhan et al., 2005). Archaeological studies (e.g., Petersen, 1970; West, 1994) indicate that ancient Peruvians exploited placer gold; how- ever, the use of mercury for amalgamation and recovery of the gold is rarely discussed or is considered to have been a European technological import. However, the volume of gold artifacts provided by Atahualpa, the Inca king, for his release from the Spanish in 1532 is hard evidence of the volume of gold in Peru as well as the advanced small-scale mining technology used by the ancient Andeans. Larco Hoyle (2001) indicates that mercury was used by the Moche (100 BCE–750 CE), in northern Peru, to amalgamate placer gold. The mercury was cleaned and recycled by squeezing the gold-bearing amalgam through a scrap of leather, and the recovered mercury was reused. This process is similar to the method described by al-Biruni (al-Hassan and Hill, 77 CE, Rome imported 4–5 metric tons of mercury annually from the mines in Spain, which was used for gold amalga- mation (D’Itri and D’Itri, 1977). As early as 600 BCE, cinnabar was used by the Greeks as a pigment to color statues (Healy, 1978). Powdered cinna- bar was used to paint Roman villas and also as a cosmetic. Researchers found that cinnabar was one of the mineral pigments used on the frescoes that were later buried by ash from volcanic eruptions at Pompeii (Lorenzi, 2004). Roman criminals and slaves were sent to work at firesetting (an ancient mining practice in which wood was burned at the face of the ore zone and water was poured on the face, causing the rock to crack and spall) in the Spanish mer- cury mines (D’Itri, and D’Itri, 1977); they subsequently died from inhaling the toxic mercury fumes released by the process. In the Middle East, according to the 11th century scien- tist Abu Rayhan al-Biruni, author of texts on mineralogy, gems, and metals, gold was processed from the ore by crush- ing, then the ore was washed and mercury was added. Gold was also recovered from the Sind River by leaving mercury in small pits dug in the bedrock in the stream. The gold- bearing sediment would wash over the puddles of mercury and the gold would amalgamate with the mercury. In both examples, the gold-bearing amalgam was then recovered and squeezed through leather to separate the gold from the mercury and recover some of the mercury. Then, as a final step, the amalgam was burned in order to volatilize the mercury and purify the gold (al-Hassan and Hill, 1986). The amalgamation process for small-scale mining of quartz veins was introduced to West Africa in the 12th cen- tury and the amalgam was similarly burned to recover the gold (Blanchard, 2006). The New World There are mercury occurrences in Guerrero, Queretaro, San Luis Potosí, and Zacatecas, Mexico. However, in the late 1500s, mercury from Peru was brought to Mexico for silver processing. Spain prohibited the exploitation of mercury in Mexico from 1680 to 1811; therefore, records of mercury mining in Mexico were inconsistent (Consejo de Recursos Minerales, 1992; Acosta y Asociados, 2001). Underground mining of cinnabar dates to the 1000 BCE in Queretaro, and it was used for rituals and celebrations (Langenscheidt, 1986; Consejo de Recursos Minerales, 1992). Archaeological evidence indicates that cinnabar was also mined at Guadalcázar, in central San Luis Potosí (Wittich, 1922; Zaragoza, 1993). In south-central Mexico, cinnabar was used as a pigment by the Olmec to decorate figures during the Pre-Classic (1200 to 400 BCE) (Martín del Campo, 2005). At the Temple of Inscriptions, Palenque, Mexico, the sarcophagus of the Maya king Pacal, who died in 683 CE, was painted with cinnabar as a toxic warning to looters. The body of Pacal and the body of a woman, perhaps
- 44. 22 MERCURY CYCLING IN THE ENVIRONMENT Powdered cinnabar was used to decorate gold masks during the Formative Period in Peru (1000–400 BCE) (De Lavalle, 1992; Shimada and Griffin, 2005); as a mural pig- ment (Muelle and Wells, 1939; Bonavia, 1985; Brooks et al., 2006); for painting warriors’ bodies and as a cosmetic for the elite Inca women (Brown, 2001); and for funeral prep- arations (Maravelaki-Kalaitzaki and Kallithrakas-Kontos, 2003; John Verano, Ph.D., anthropologist, Dumbarton Oaks, Washington, DC, oral communication, December 12, 2005). Wooden funerary figures painted with cinnabar were recovered from Huaca Tacaynamo and Huaca El Dragón, both of which are Chimu (800–1450 CE) ceremonial sites in northern Peru (Jackson, 2004). Mollusk shells, some with cinnabar found in the interior of the shell, suggests that the shells were used as ancient palettes (Petersen, 1970). A variety of “reds” were readily available in ancient Peru. Sources for “red” included plant-derived achiote, Spondylus (a mollusk), insect-derived cochineal, feathers, plant pig- ments, and mineral-derived cinnabar, goethite, hematite, and jasper. However, ancient Peruvians selectively used powdered cinnabar for funeral preparations (Shimada and Griffin, 2005; John Verano, Ph.D., anthropologist, Dumbarton Oaks, Washington, DC, oral communication, January 25, 2006). Therefore, in ancient Peru and else- where in the New World, as in the Old World, the question persists as to whether or not cinnabar was used because of its blood-red life symbolism or because of its toxicity and preservative qualities. In 1566, the mercury mines of Huancavelica were redis- covered by the Spaniards. In 1571, mercury once again became an important industrial metal in mining when Pedro Fernandez de Velasco used mercury for silver amal- gamation at Porco and Potosí, Bolivia (Arana, 1901). Until that time, mercury had been transported from Spain for use in the New World, and Spanish shipwrecks, which still contain mercury, are known in Samaná Bay, Dominican Republic, and Cartagena Bay, Colombia (Petersen, 1979). In the late 1500s, mercury from Huancavelica was also used in the “patio process” for silver processing in Chile, Bolivia, and Mexico. Salt, mercury, and vitriol (mixed copper and iron sulfates) were mixed with crushed silver ore that con- tained argentite (Ag2S), cerargyrite (AgCl), or pyragyrite (Ag3SbS3), also known as the “dry ores,” in a large open area, or patio, and at Potosí, Bolivia, the cold climate required that the patios be heated from below to speed silver pro- duction, which also increased mercury losses (Craddock, 1995). Mercury’s role was well established in mineral pro- cessing in Spanish Colonial Peru and adding mercury, “el azogado,” was an essential step in silver recovery (Del Busto Duthurburu, 1996). Conclusion Since ancient times, mercury has been used for a variety of industrial applications and one of those, its use for arti- sanal gold mining continues today in many parts of the 1986) for mercury recovery. Posnansky (in Petersen, 1970) describes a site near Machu Picchu where amalgamation was used, before the arrival of the Europeans, to recover gold from crushed quartz vein material. Kaufmann Doig (1978) also describes the use of mercury for gilding precon- tact copper artifacts with gold. The Inca (1300–1533 CE), as did the Romans, recognized the health hazards of mercury and that exposure to mercury and cinnabar during mining and retorting would cause the ancient miners “to shake and lose their senses”; therefore, the use of mercury by the Inca declined (Garcilaso de la Vega, in Larco Hoyle, 2001). As in the Old World, whether or not the ancient Andean metallurgists retorted cinnabar for mercury is controversial; however, retorts have been found near the mercury mines at Huancavelica (Kendall Brown, Ph.D., professor, Brigham Young University, written com- munication, May 9, 2003). Mercury was recovered from drainages and, according to Petersen (1970), from retort- ing cinnabar near Huancavelica. And, only 15 km from Huancavelica is Atalla, an archaeological site interpreted as an ancient cinnabar pigment production center (Burger and Matos, 2002). Isotopic data on mercury in lake sediments, combined with 14C geochronology, indicate that mercury mining at Huancavelica began around 1400 BCE. and that mercury production peaked at approximately 500 BCE and at 1450 CE, corresponding to the heights of Chavin and Inka rule, respectively, in the region (Cooke et al., 2009). In describing the early history of the amalgamation pro- cess, Craddock (2000) indicated that if mercury had been used, then trace amounts of mercury would be present in the chemical analyses of the gold foils. The implication is that the quantity of mercury used in the amalgamation process would have been reduced by firing the gold, which would have volatilized most, but not all, of the mercury. Therefore, using SEM-EDX (scanning electron micro- scope combined with energy dispersive x-ray spectroscopy), Ramage and Craddock (2000) analyzed gold samples from Sardis and found mainly gold and silver. They concluded that since mercury was not detected, no mercury had been used to amalgamate the gold. However, using induced coupled plasma (ICP) analysis, 8 ppm mercury was found in gold after the gold–mercury amalgam (⬎300,000 ppm mercury) was burned (refogado), to volatilize the mercury, in the modern gold shops in Madre de Dios, Perú. From 12.3 to 13.9 ppm mercury was found in worked gold artifacts from Huaca la Ventana, a Middle Sicán (900–1200 CE) site at Lambayeque, Perú, and low levels of mercury were found in precontact worked gold samples from Colombia and Ecuador. Similarly low levels of mercury in the ICP analyses of modern refogado gold and precontact worked gold are consistent with a com- parable, ancient small-scale mining technology that would have used mercury to amalgamate the fine-grained placer and vein gold, and then, as now, burning the amalgam to volatilize the mercury, beautify, and recover the gold for craft production (Brooks et al., 2009).
- 45. INDUSTRIAL USE OF MERCURY IN THE ANCIENT WORLD 23 toxicity of mercury fumes and cinnabar powder by the Romans, the Maya, and the Inca has largely been overrid- den by mercury’s widespread usefulness in modern indus- trial applications. world. The selective use of powdered cinnabar as a preser- vative in ancient funeral rituals to stop biologic decom- position can only be inferred; however, now, the toxicity of cinnabar is well established. Age-old awareness of the References Acosta y Asociados. 2001. Inventory of sites in Mexico with elevated concentrations of mercury, Acosta y Asociados Project CEC-01, Agua Prieta, Sonora, Mexico. http://www.chem .unep.ch/mercury/2001-gov-sub/sub79govatt2.pdf (accessed October 10, 2007). Agricola, G. 1556. De Re Metallica: London. Translated by H.C. Hoover and L.H. Hoover and reprinted in 2005 from the 1912 edition, New York: Kessinger. al-Hassan, A.Y., D.R. Hill. 1986. Islamic technology, an illustrated history. Cambridge: Cambridge University Press, p. 247. al-Saleh, I., and I. al-Doush. 1997. Mercury content in skin lightening creams and potential health hazards to the health of Saudi women. Journal of Toxicology and Environmental Health 51(1): 123–145. Arana, P.P. 1901. Las minas de azogue del Peru [Mercury mines of Peru]. Lima: Imprenta El Lucero, p. 6. Barnes, J.W., and E.H. Bailey. 1972. Turkey’s major mercury mine today and how it was mined 8000 years ago. World Mining 25(4): 49–55. Blanchard, I. 2006. African gold and European markets, c.1300-c.1800. Presented at the International Institute of Economic Studies, Volume and Commercial Relations between Europe and the Islamic World, University of Edinburgh-CEU-Budapest, 1-5 May. http://www .ianblanchard.com (accessed August 27, 2008). Bonavia, D. 1985. Mural painting in ancient Peru. Bloomington: Indiana University Press, p. 179. Brooks, W.E. 2007. Mercury, chapters in U.S. Geological Survey Minerals Yearbook. http://minerals.usgs.gov (accessed December 15, 2008). Brooks, W.E., and G.R. Matos. 2005. Mercury recycling in the United States in 2000, U.S. Geological Survey Circular 1196-U. http://minerals.usgs.gov (accessed August 27, 2007). Brooks, W.E., V. Piminchumo, H. Suarez, J.C. Jackson, and J.P. McGeehin. 2006. Mineral pigments from Huaca Tacaynamo, northern Peru. Geological Society of America Abstracts with Programs 38(7): 233. Brooks, W.E., E. Sandoval, M. Yepez, and H. Howard. 2007. Peru mercury inventory. U.S. Geological Survey Open-File Report 2007-1252. http://pubs.usgs.gov/of/2007/1252 (accessed October 15, 2007). Brooks, W.E., G. Schworbel, and L.E. Castillo. 2009. Mercury and small-scale gold mining in ancient Peru. Geological Society of America Abstracts with Programs 41(7): 435. Brown, K.W. 2001. Workers’ health and colonial mercury mining at Huancavelica, Peru. 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The Chimu sculptures of Huacas Tacaynamo and El Dragón, Moche Valley, Peru. Latin American Antiquity 15(3): 298–322. Kapp, L., H. Kapp, and A. Yoshira. 1987. The craft of the Japanese sword. Tokyo: Kodansha International. Kaufmann Doig, F. 1978. Manual de arqueologia Peruana [Manual of Peruvian archaeology]. Lima, Peru: Ediciones Peisa, p. 747. Langenscheidt, A. 1986. El cinabrio y el azogue en el Mexico antiguo [Cinnabar and mercury in ancient Mexico]. Revista Minero-Americana, Mexico City, 17(1): 24–29. Larco Hoyle, R. 2001. Los Mochicas, tomo II [The Moche, volume II]. Lima: Museo Arqueologico Rafael Larco Herrera, pp. 128, 135. Leicester, H.M. 1961. The historical background of chemistry. New York: Wiley, p. 12. Lorenzi, R. 2004. Pompeii artists painted the town red. http://www.abc.net.au (accessed January 15, 2007). Maravelaki-Kalaitzaki, N., and N. Kallithrakas-Kontos. 2003. Cinnabar find in Cretan Hellenistic tombs, preservative or cosmetic purposes. 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- 47. PART TWO METHODS FOR RESEARCH, MONITORING, AND ANALYSIS
- 49. 27 CHAPTER 3 Analytical Methods for Measuring Mercury in Water, Sediment, and Biota BRENDA K. LASORSA, GARY A. GILL, and MILENA HORVAT PHYSICAL AND CHEMICAL PROPERTIES OF MERCURY SPECIES Metallic Mercury Inorganic Ions of Mercury Organo-Mercury Compounds DETERMINATION OF TOTAL MERCURY AND INORGANIC MERCURY SPECIES Total Mercury and Inorganic Mercury Species in Water Determination of Total Mercury in Natural Waters TOTAL MERCURY IN SOLID MATRICES Determination of Total Mercury in Solid-Phase Materials Other Total Mercury Analytical Methods DETERMINATION OF ORGANO-MERCURY SPECIES Occurrence of Organo-Mercury Species in Natural Waters Sampling and Storage Determination of Organo-Mercury Compounds in Aqueous Media DETERMINATION OF THE CHEMICAL AND PHASE SPECIATION OF MERCURY IN NATURAL WATERS Methods to Assess Divalent Mercury–Organic Matter Interactions Phase-Speciation Methods ORGANO-MERCURY SPECIES IN OTHER ENVIRONMENTAL MATRICES Sampling and Storage Determination of Organo-Mercury in Solid Matrices Other Methods Other Organo-Mercurials FRACTIONATION OF MERCURY IN SOILS AND SEDIMENTS USE OF MERCURY ISOTOPIC AND RADIOCHEMICAL TRACERS CALIBRATION AND QUALITY CONTROL SUMMARY AND CONCLUSIONS specific analytical equipment and contamination-free methods. These improvements allow for the determina- tion of total mercury as well as major species of mercury to be made in water, sediments and soils, and biota. Ana- lytical methods are selected depending on the nature of the sample, the concentration levels of mercury, and what species or fraction is to be quantified. The terms “speciation” and “fractionation” in analytical chemistry were addressed by the International Union for Pure and Applied Chemistry (IUPAC) that published guidelines (Templeton et al., 2000) or recommendations for the defi- nition of speciation analysis: “Speciation analysis is the analytical activity of identifying and/or measuring the Mercury (Hg) exists in a large number of physical and chemical forms with a wide range of properties. Con- version between these different forms provides the basis for mercury’s complex distribution pattern in local and global cycles and for its biologic enrichment and effects. Since the 1960s, the growing awareness of environmen- tal mercury pollution has stimulated the development of more accurate, precise and efficient methods of quan- tifying mercury and its compounds in a wide variety of matrices. During recent years new analytical techniques have become available that have contributed significantly to the understanding of mercury chemistry in natural systems. In particular, these include ultrasensitive and
- 50. 28 RESEARCH, MONITORING, AND ANALYSIS quantities of one or more individual chemical species in a sample. The chemical species are specific forms of an element defined as to isotopic composition, electronic or oxidation state, and/or complex or molecular structure. The speciation of an element is the distribution of an ele- ment amongst defined chemical species in a system. In case that it is not possible to determine the concentration of the different individual chemical species that sum up the total concentration of an element in a given matrix, meaning it is impossible to determine the speciation, it is a useful practice to do fractionation instead. Fractionation is the process of classification of an analyte or a group of analytes from a certain sample according to physical (e.g. size, solubility) or chemical (e.g. bonding, reactivity) properties.” Typical concentrations of Hg and monomethylmer- cury (MMHg) found in a variety of environmental matrices are given in Table 3.1. This table is by no means exhaustive, but it does illustrate the wide range of con- centrations that must be quantified in a great variety of matrices of varying complexity in order to understand Hg cycling in the environment and its effects on human and ecosystem health (Figure 3.1). The selection of an analytical technique that is rigorous enough to over- come any matrix issues yet sensitive enough to produce meaningful data in the range of typical concentrations is critical to the success of environmental Hg research. Physical and Chemical Properties of Mercury Species Metallic Mercury Elemental mercury (Hg0), referred to as Hg vapor when present in the atmosphere, or as metallic Hg in liquid form, is of considerable toxicologic as well as of environmental importance because it has a relatively high vapor pressure (14 mg m1 at 20°C, 31 mg m3 at 30°C) and appreciable water solubility (~60 g L1 at room temperature). Because it is highly lipophilic, elemental Hg dissolves readily in fatty compartments. Of equal significance is the fact that the vapor exists in a monatomic state. Inorganic Ions of Mercury Many salts of divalent mercury, Hg(II), are readily soluble in water, such as mercury sublimate (HgCl2, 62 g L1 at 20°C), and, thereby, highly toxic. In contrast, the water solubility of cinnabar (HgS) is extremely low (~10 ng L1), and, correspondingly, HgS is much less toxic than HgCl2 (Simon and Wuhl-Couturier, 2002). The extremely high affinity of the free mercury ion, Hg2, for sulfhydryl groups of amino acids such as cysteine and methionine in enzymes explains its high toxicity. However, its affin- ity to SeH-groups is even greater, which may explain the table 3.1 Typical Ranges of Environmental Mercury Concentrations Matrix Total Hg MMHg Freshwater (rivers) 0.3–100 ng/L 0.01–2 ng/L Freshwater (lakes) 0.2–50 ng/L 0.01–5 ng/L Seawater 0.2–5 ng/L 0.01–0.5 ng/L Rain 1–20 ng/L 0.01–0.5 ng/L Snow 1–150 ng/L 0.01–1 ng/L Lake sediment 10–1000 ng/g 0.01–100 ng/g Marine sediment 5–2000 ng/g 0.05–100 ng/g Soils 5–500 ng/g 0.05–20 ng/g Terrestrial mammals 0.01–0.2 g/g (wet) 0.005–0.15 g/g (wet) Freshwater fish 0.01–2 g/g (wet) 0.005–2 g/g (wet) Marine fish 0.01–13 g/g (wet) 0.01–12 g/g (wet) Marine mammals 0.03–35 g/g (wet) 0.02–35 g/g (wet) Algae 0.01–0.2 g/g 0.001–0.1 g/g Blood 0.2–50 g/L 0.2–50 g/L Human hair 0.1–10 g/g 0.1–10 g/g SOURCE: Pirrone and Mahaffey, 2005; personal experience of the authors.
- 51. ANALYTICAL METHODS FOR MEASURING MERCURY 29 (Horvat, 2005). Monomethylmercury compounds are of the greatest concern, as these highly toxic compounds are formed by microorganisms in sediments and bio-accumulated and biomagnified in aquatic food chains, thus resulting in exposures of fish-eating populations, often at levels exceed- ing what is regarded as safe. MMHg is also bio-accumulated and biomagnified in terrestrial food chains. Although it is less researched and not typically an issue for human con- sumption, this is still a major concern for wildlife health. Determination of Total Mercury and Inorganic Mercury Species There are numerous analytical techniques available for the analysis of total Hg and the inorganic Hg species in envi- ronmental samples. A brief summary of the methods avail- able for analysis of Hg species in environmental samples is given in Table 3.2. Traditional analytical methods for Hg detection are largely based upon room temperature, gas phase (often referred to as cold vapor), and atomic absorp- tion techniques, but inductively coupled plasma mass spec- trometry (ICP-MS) can also be used for parts-per-million to higher parts-per-billion level measurements in solids. More recently, cold-vapor atomic fluorescence techniques have been developed that allow determination at parts- per-trillion and subparts-per-trillion concentration levels. The most appropriate specific method is dictated by the detection limit required to produce meaningful data, as well as the sample size, sample matrix and potential inter- ferences specific to the method. protective role of selenium from Hg intoxication (Yaneda and Suzuki, 1997). Monovalent Hg, Hg (I), is found only in dimeric salts such as Hg2Cl2 (calomel), which is sparingly soluble in water and therefore correspondingly much less toxic than HgCl2 (sublimate). Organo-Mercury Compounds Organo-Hg compounds consist of diverse chemical structures in which divalent Hg forms one covalent bond (R-Hg-X) or two covalent bonds (R-Hg-R) with carbon. In environmen- tal samples, organo-Hg compounds are, for the most part, limited to the alkylmercurials monomethylmercury, mono- ethylmercury and, more rarely, dimethylmercury, as well as alkoxymercury compounds, and arylmercurials (phen- ylmercury). Organo-Hg cations (R-Hg) form salts with inorganic and organic acids (e.g., chlorides and acetates), and react readily with biologically important ligands, nota- bly sulfhydryl groups. Organo-mercurials also pass easily across biologic membranes, since the halides (e.g., CH3HgCl) and dialkylmercury are lipid-soluble. The major difference among these various organo-Hg compounds is that the sta- bility of carbon-mercury bonds in vivo varies considerably. Thus, alkylmercury compounds are much more resistant to biodegradation than either arylmercury or alkoxymercury compounds. The term “methylmercury” is used through- out this text to represent monomethylmercury (MMHg) compounds. In many cases, the complete identity of these compounds is not known except for the MMHg cation, CH3Hg, which is associated either with a simple anion, like chloride, or a large charged molecule (e.g., a protein) Air Air Sunlight Sunlight Hg0 (g) Hg(II) Sunlight Hg(II) g g (g) g( ) Hg(II) S li ht Hg0 (g) Sunlight Hg(II) CH Hg+ Hg0 (g) Bacteria Hg(II) Hg (g) Biota Hg(II) Phyto - CH3Hg+ Hg (g) Hg(II) Biota Hg MeHg plankton g colloid MeHg colloid Z colloid Zoo - plankton Hg(II) MeHg H II plankton particle particle particle particle Land Water Fish Land Fish Bacteria CH3Hg+ Hg(II) Bacteria 3 g Hg(II) H S ( ) HgS (s) S di t Sediment g( ) FIGURE 3.1 A biogeochemical cycle of mercury in the environment, illustrating the common forms of mercury often quantified.
- 52. 30 RESEARCH, MONITORING, AND ANALYSIS particulate-bound Hg forms. Mercury also forms numer- ous stable complexes with well-defined organic ligands (e.g., ethylenediaminetetraacetic acid [EDTA]) and with dissolved organic matter (DOM) to form organic mercury compounds. Biologic transformations can convert Hg(II) to gaseous elemental Hg and methylated Hg forms (see Figure 3.1). In tissues, mercury can be present in both inorganic and organo-Hg forms, with higher trophic level species usually containing predominantly MMHg. In sed- iments, mercury tends to adsorb preferentially to carbon- based particles. To perform a meaningful total Hg analysis, it is essen- tial to perform a suitable preparation step to release the Hg from whatever matrix or complexes in which it may reside. Another factor that must be weighted in choosing a suitable analytical method is the recognition that mer- cury can exist in a wide variety of chemical forms that may or may not be liberated for analysis by the procedures adopted. Illustrated in Figure 3.2 are the various fractions or pools of inorganic Hg(II) that can exist in natural water systems. The common aqueous species of inorganic Hg(II) in oxygenated freshwater are Hg(OH)2 0, and HgCl2 0. In seawater, the dominant inorganic forms are the chlo- ride species (HgCl4 2, HgCl3 1, etc). In suboxic to anoxic waters, polysulfide species can dominant (e.g., HgS0) if sulfide concentration levels exceed Hg concentration lev- els. Hg(II) also strongly interacts with colloids and sus- pended particles in aqueous systems to form colloidal or table 3.2 Selected Methods for the Analysis of Mercury Analyte Matrix Detector Reference or EPA method Typical MDL Total Hg Water CVAAS EPA Method 245.1 5–10 ng/L Total Hg Water CVAFS EPA Method 245.7 0.5–5 ng/L Total Hg Water CVAFS EPA Method 1631 0.1–0.3 ng/L Total Hg Water ICP-MS EPA Method 200.8 10 ng/L Total Hg Water ICP-AES EPA Method 200.7 200 ng/L Elemental Hg Water CVAFS EPA Method 1631 moda 0.1–0.3 ng/L Reactive Hg Water CVAFS EPA Method 1631 modb 0.1–0.3 ng/L MMHg Water CVAFS EPA Method 1630 (draft) 0.01–0.05 ng/L Total Hg Sediment CVAAS EPA Method 245.5 5–10 ng/g Total Hg Sediment CVAAS EPA Method 7471 10–50 ng/g Total Hg Sediment DTDAAS EPA Method 7473 5–10 ng/g Total Hg Sediment CVAFS EPA Method 1631 appendix 0.5–1 ng/g MMHg Sediment CVAFS EPA Method 1630 modc 0.01–0.05 ng/g MMHg Sediment GC-ICP-MS Bjorn et al. (2007)c 0.01–0.05 ng/g Total Hg Tissue CV AAS EPA Method 245.6 5–10 ng/g Total Hg Tissue DTDAAS EPA Method 7473 5–10 ng/g Total Hg Tissue CVAFS EPA Method 1631 appendix 0.5–1 ng/g Total Hg Blood ICP-MS Palmer et al. (2006) 0.17 g/L Total Hg Blood FI-AAS Palmer et al. (2006) 0.6 g/L MMHg Tissue CVAFS EPA Method 1630 modd 0.5–2 ng/g AAS atomic absorption spectrometry; CVAAS cold-vapor atomic absorption spectrometry; CVAFS cold-vapor atomic fluorescence spectrometry; FI Flow Injection; GC gas chromatography; ICP-AES inductively coupled plasma atomic emission spectrometry; ICP-MS inductively coupled plasma mass spectrometry; MDL Method Detection Limit; DTD Direct Thermal Decomposition. a. Without oxidation or reduction. b. Without oxidation. c. Using extraction or distillation to isolate MMHg. d. Using KOH/methanol digestion to release MMHg (Bloom 1989)
- 53. ANALYTICAL METHODS FOR MEASURING MERCURY 31 aqueous samples over the past 15 years (Gill and Fitzger- ald, 1985, 1987; Bloom, 1995; Fitzgerald, 1999; Parker and Bloom, 2005). As noted previously, the total Hg in a water sample can be composed of several distinct forms or pools, includ- ing “dissolved” Hg (usually operationally defined as that mercury passing through a 0.45-µm filter), Hg associated with particulate and colloidal matter, volatile elemental Hg0, and labile (or reactive) Hg(II). All these forms can all be quantified as long as the samples are collected and pre- served properly for the species to be determined. SAMPLING AND STORAGE Collection and handling of aqueous samples for low-level determination of Hg must address several factors, includ- ing whether or not the sample is representative, possible interconversion processes, contamination, and preserva- tion and storage of the matrix before analysis. The mea- surement (sampling and analysis) protocol must be care- fully designed if speciation of Hg forms in the aqueous samples is intended. The stability of Hg in solution is affected by many factors, including: (a) the concentration of Hg and its compounds, (b) the type of water sample, (c) the type of containers used, (d) the cleaning and pretreat- ment of the containers, and (e) the preservative added. Table 3.3 lists recommended sample-collection containers, hold times, and preservation methods for the most com- mon environmental samples collected for inorganic or total Hg analysis. The best materials for sample storage and sample pro- cessing are Pyrex and silica (quartz) glass or Teflon This removes any matrix interferences with the analysis that result in a biased determination and allows the detec- tion method to quantify the mercury. Finally, because Hg is ubiquitous in the environment and is used in so many chemical manufacturing processes, find- ing suitably clean reagents for sample preparation or diges- tion steps can be difficult. For low-level aqueous mercury measurements, it is essential, therefore, that all reagents used be rigorously checked for Hg contamination prior to use and that all laboratory ware that comes in contact with the sample be of appropriate materials and be rigorously cleaned to maintain contamination at suitably low levels (Gill and Fitzgerald, 1985, 1987; Bloom, 1994; Parker and Bloom, 2005). Total Mercury and Inorganic Mercury Species in Water Recent improvements in analytical methods have dem- onstrated that much of the historical data for total Hg in environmental water samples collected prior to the early 1990s was biased, either high because of contami- nation during sampling and analysis or low because of improper sample collection containers or improper pres- ervation techniques (Fitzgerald, 1999). Problems arising in the analysis of total Hg in natural water samples are not connected with the final measurement, but rather with difficulties associated with contamination-free sam- pling and losses due to volatilization and adsorption dur- ing storage. There have been remarkable improvements in sampling and analytical techniques that have resulted in a dramatic increase in the reliability of data for Hg in FIGURE 3.2 Competition for the partitioning of the free mercury ion into various pools or fractions in natural waters.
- 54. 32 RESEARCH, MONITORING, AND ANALYSIS surface waters is usually performed by hand, using arm- length plastic gloves. Samples are taken upwind of a rubber raft or a fiberglass boat. When it is not possible to collect a grab sample, acid-cleaned, contamination-free sampling devices (e.g., Teflon or Go-Flo samplers) are commonly used for the collection of water samples. Alternatively, the water can be pumped through acid-cleaned Teflon tub- ing using a peristaltic pump. Precipitation samples can be collected by automatic samplers, with in-line filtration if desired (Landing et al., 1998). Water samples should be collected in acid-cleaned glass or Teflon bottles. If the samples are to be analyzed for dis- solved Hg, the sample must either be filtered using a peri- staltic pump with precleaned in-line filters during sample collection or within 48 hours of collection once samples are returned, on ice, to the laboratory. Samples for total or dissolved Hg should be preserved as soon as possible after collection (generally within 48 hours) with high-purity, low-mercury-content HCl (typically 0.5%) or HNO3 (typi- cally 0.2%). Water samples for the analysis of total mer- cury only may also be preserved by direct addition of the oxidizing agent 0.2N BrCl (typically 0.5%) as described in Environmental Protection Agency (EPA) Method 1631 (EPA, 2002). If MMHg is also to be analyzed along with total Hg on the same sample, only HCl preservation should be used, as HNO3 can destroy MMHg. Water sam- ples for the determination of elemental Hg should not be preserved with acid and the Hg0 isolated from the solution immediately upon collection to avoid loss from solution. Samples for the analysis of reactive Hg cannot be pre- served and must be stored cold and processed as soon as possible after collection (Parker and Bloom, 2005). Ideally, samples for reactive mercury are reduced and purged to gold amalgamation traps in the field immediately after collection. Containers and other sampling equipment that come into contact with water samples should be made of borosilicate glass, Teflon, or silica glass and rigorously Polytetrafluoroethylene (PTFE) or fluorinated ethylene pro- pylene (FEP). Significant contamination can occur with plastics such as polyethylene and polypropylene, and therefore these are not recommended for aqueous samples. Plastic containers cannot be as rigorously cleaned as glass or Teflon and are highly permeable to vapor-phase Hg0, allowing Hg to readily freely diffuse into (or out of) sam- ples depending on the concentration gradient between the sample and surrounding air (Gill and Fitzgerald, 1987). Rigorous cleaning procedures must be used for all labora- tory ware and other equipment that comes into contact with samples. There are several cleaning procedures that are suitable for laboratory ware and sampling equipment: (1) aqua regia treatment followed by soaking in dilute (~5–10%) nitric acid for a week; (2) soaking in a hot oxidiz- ing mixture of KMnO4 and K2S2O8, followed by NH4OCl rinsing and soaking for a week in 5M HNO3; (3) soaking in a 1:1 mixture of concentrated chromic and nitric acids for a few days; and (4) soaking in a BrCl solution (mixture of HCl and KBrO3). Teflon ware is usually cleaned in hot concentrated HNO3 for 48 hours, followed by numerous rinses with a high- purity (low Hg content) laboratory water supply (e.g., 18 M deionized water or double distilled water) and dried on a class-100 clean air bench. Items are then generally placed in a sealed plastic bag to avoid dust contamination and stored in an environment known to be low in atmo- spheric mercury content. Some authors recommend stor- age of laboratory ware in dilute HNO3 or HCl acids until use. For collection of samples to be analyzed for both total Hg and MMHg analyses, the bottles must be prepared with extreme caution to ensure that the containers do have residual HNO3 from the cleaning process. Soaking of laboratory ware, particularly Teflon, in hot (70°C) 1% HCl removes any traces of oxidizing compounds that may sub- sequently destroy MMHg in solution. Water samples are often collected by grab sampling upstream of sources of contamination. Collection of table 3.3 Recommended Containers and Preservation Methods for Inorganic and Total Mercury Measurements Analyte Matrix Preservative Container Hold time Total Hg Water 0.5% HCl Teflon or glass 90 daysa Total Hg Water 0.5% HCl Teflon or glass 180 daysb Elemental Hg Water NA Teflon or glass 0 daysb Reactive Hg Water 4 2°C Teflon or glass 2–3 daysb Total Hg Sediment Frozen/freeze-dried Teflon, glass or plastic 1 yeara Total Hg Tissue Frozen/freeze-dried Teflon, glass or plastic 1 yeara NA not applicable. a. According to EPA Method 1631. b. According to Parker and Bloom 2005.
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- 56. A LARGE DARK BIRD SWOOPING DOWN. Page 142 The White Cock spoke at almost the same time. “Er-ru-u-u-u-u! Run! Run!” Then all the Hens and Pullets put down their heads and ran as fast as they could for the poultry-house, which was near. The Shanghai Cock and the White Cock waited to let them pass, and then followed
- 57. in after them. It is a law among fowls that the Cocks must protect the Hens from all danger. Because these two had to wait so long for the Hens and Pullets to get inside, they were still where they could see quite plainly when the bird, a large Eagle, swooped down to the roof of the carriage- house and caught the Young Cock up in his talons. The Young Cock had not seen him coming until he was almost there. He had been too much interested in watching the fowls on the ground below. When he saw the Eagle it was too late to get away. As the Eagle flew upward once more, all the fowls ran out to watch him. They could see the Young Cock struggling as the sharp talons of the Eagle held him tightly. “Poor fellow!” said the Pullets. The Cocks were wise enough to keep still. The Hens murmured something to themselves which nobody else could understand. Only the Plymouth Rock Hen said very much about it, and that was because she had children to bring up. One of the Young Cock’s tail- feathers floated down from the sky and fell into their yard. “Leave it right there,” she said. “Leave it there, and every time you look at it, I want you to remember that the Cock to whom it belonged might now be having a pleasant time on this farm, if he had not been quarrelsome and bragged.”
- 60. I THE GUINEA-FOWLS COME AND GO T was only a few days after the Young Cock had been carried away by the Eagle, that the Man drove back from town with a very queer look upon his face. A small crate in the back end of the light wagon contained three odd-looking fowls. The Little Girls left their mud pies and ran toward the wagon. When they saw the crate, they ran into the house and called their mother to come out also. “What have you now?” said she, as she stepped onto the side porch. “Guinea-fowls,” answered the Man. “Just listen to this letter.” He drew it from his pocket and read aloud: “I send you, by express, a Guinea-Cock and two Guinea-Hens. They were given to me, and I have no place for keeping them. I remember hearing that they are excellent for scaring away Crows, so I send them on in the hope that they may be useful to you. If you do not wish to keep them, do what you choose with them.” As he read three small and perfectly bald heads were thrust through the openings of the crate and turned and twisted until their owners had seen everything around. “I don’t know anything about Guinea- fowls,” said the Man, “but I will at least keep these long enough to find out. I have seen the Crows fly down and annoy the Hens several times, and it may be that these are just what we need.” He took the crate down and opened it carefully. The three fowls that walked out looked almost exactly alike. All had very smooth and soft coats of black feathers covered with small round white spots. They were shaped quite like Turkeys, but were much smaller, with gray- brown legs, and heads which were not feathered at all. The skin of their faces and necks was red, and they had small wattles at the corners of their mouths. Bristle-like feathers stood out straight around the upper part of their necks, and below these were soft
- 61. gray feathers which covered the neck and part of the chest. They walked directly toward the barnyard, where some of the farm fowls were picking up an early dinner. “Ca-mac!” said they “Ca-mac! Ca- mac! We want some too.” Now the farm fowls were not especially polite, not having come of fine families or been taught good manners when they were Chickens, yet they did not at all like to have newcomers speak to them in this way. They noticed it all the more, because when the White Plymouth Rocks came they had acted so very differently. They stepped a little to one side, giving the Guinea-fowls enough room in which to scratch and pick around as they had been doing, but they did not say much to them. The Gobbler was strutting back and forth among the smaller fowls. He disliked living with them as much as he had to now, but the Hen Turkeys would have nothing to say to him because he annoyed their Chicks. They went off with their children and left him alone, and, as he wanted company of some sort, he took what he could get. He thought it might be a good plan to make friends with the Guinea- fowls. “Good-morning,” said he. “Have you come here to stay?” “We shall stay if we like it,” answered the Guinea-Cock. “We always do what we like best.” “Humph!” said the Shanghai Cock to himself. “Remarkable fowls! Wonder what the Man will think about that.” “I hope you will like it,” said the Gobbler, who was so lonely that he really tried hard to be agreeable. “I understand quite how you feel about doing as you like. I always prefer to do what I prefer.” “We do it,” remarked one of the Guinea-Hens, as she chased the Brown Hen away from the spot where she had been feeding, and swallowed a fat Worm which the Brown Hen had just uncovered.
- 62. “Yes,” said the other Guinea-Hen, “I guess we are just as good as anybody else.” “Is there plenty to eat here?” asked the Guinea-Cock. “Plenty,” answered the Gobbler. “It is much better than it used to be. There is a new Man here, and he takes better care of his fowls than the Farmer did. He doesn’t carry red handkerchiefs either.” “I don’t care what kind of handkerchiefs he carries,” said the Guinea- Cock. “What makes you talk about such things?” “You would know what makes me speak of them if you were a Gobbler,” was the answer. “I cannot bear red things. I cannot even eat my corn comfortably when anything red is around. You see it is quite important. Anything which spoils a fellow’s fun in eating is important.” “Nothing would spoil my fun if I had the right sort of food,” remarked the Guinea-Cock. Then he turned to the Guinea-Hens. “Come,” he said. “We have eaten enough. Let us walk around and see the place.” All three started off, walking along where-ever they chose, and stopping to feed or to talk about what they saw. Anybody could tell by looking at them that they were related to the Turkeys, but the Gobbler had not cared to remind them of that. He was looking for more company during the time when his own family left him so much alone. He knew that before very long the Turkey Chicks would be too large to fear him, and that when that time came, their mothers and they would be willing to walk with him. Then he would have less to do with the other poultry, and might not want three bad-mannered Guinea-fowl cousins tagging along after him. Whenever the three met another fowl, they talked about him and said exactly what they thought, and if they passed a Hen who had just found a choice bit of food, they chased her away and ate it themselves. Sometimes they even chased fowls who were not in
- 63. their way and who were not eating things that they wanted. It seemed as though they had simply made up their minds to do what they wanted to do, whenever and wherever they wished. They did not make much fuss about it, and if you had seen them when they were doing none of these mean things, you would have thought them very genteel. You would never have suspected that they could act as they did. The Gander and the Geese passed near the Guinea-fowls and the Guinea-fowls did not chase them. They were not foolish enough to annoy people so much larger than they. It is true that the Hens were larger than they, yet the Guinea-fowls could make them run every time. If they had troubled the Geese, it might have ended with the Guinea-fowls doing the running. And the Guinea-fowls were cowards. They would never quarrel with people unless they were sure of beating. “S-s-s-s-s-s-s!” said the Gander. “Are we to have that sort of people on this farm? If we are, I would rather live somewhere else. I do not see why there should be any disagreeable people anyway.” “There should not be,” said the Geese, who always agreed with everything the Gander said, and who really believed as he did about this. “Disagreeable people should be sent away, or eaten up, or something.” Both the Gander and the Geese thought themselves exceedingly agreeable, and so they were—when everything suited them. At other times they were often quite cross. Many people act like this, and seem to think it very sweet of them not to be cross all the time. Truly agreeable people, as you very well know, are those who can keep pleasant when things go wrong. “Ca-mac!” said the three Guinea-fowls together. “There are some of those stupid Geese, who are always walking around and eating grass that is too short for anybody else. They eat grass, and grow feathers for Farmers’ Wives to pluck off. When we have gone to the trouble of
- 64. growing a fine coat of feathers, we keep them as long as we wish, and then they drop out, a few at a time. If anybody wants our feathers, he must follow around after us and pick them up.” Before night came, the Guinea-fowls had met and annoyed nearly all the poultry on the place. They had even made dashes at the smallest Chickens and frightened them dreadfully. The Man had been too busy to see much of the trouble that they made, but his Little Girls noticed it, for they had been watching the Guinea-fowls and hoping to find some of their beautiful spotted feathers lying around. When the Little Girls were eating their supper of bread and milk, they told their father about it. “They walk around and look too good for anything,” said the brown- haired one, “but whenever they get a chance they chase the Hens and the Chickens.” “Yes,” said the golden-haired Little Girl, “I even saw one of them scare the Barred Plymouth Rock Hen, the one who ate bread and salt with you.” “That is very bad,” said the Man, gravely. “Any fowl that troubles the Barred Plymouth Rock Hen must be punished.” “What will you do to them?” asked the golden-haired Little Girl. “I think you will have to shut them up. You couldn’t spank them, could you? Not even if you wanted to ever so much.” “I shall decide to-night how to punish them,” said the Man, “and then in the morning we will see about it.” When he spoke he did not know how much time he would spend in thinking about the Guinea- fowls that night. When it was time for them to go to roost, the Guinea-fowls fluttered and hopped upward until they reached quite a high branch in the apple-tree by the Man’s chamber window. Then, instead of going to sleep for the night, as one would think they would wish to do, they took short naps and awakened from time to time to visit with each
- 65. other. It is true that they had seen much that was new during the day, and so had more than usual to talk about, but this was really no excuse, because they had the habit of talking much at night and would have been nearly as noisy if nothing at all had happened. The Man was just going to sleep when they awakened from one of their naps and began to chat. “Ca-mac! Ca-mac!” said one. “I suppose those stupid fowls in the poultry-house are sound asleep, with their heads tucked under their wings. What do you think of the company here?” “Good enough,” said another. “I don’t like any of them very much, but you can’t expect Geese and Ducks to be Guinea-fowls. We don’t have to talk to them. The Gobbler is trying to be agreeable, and when the Hen Turkeys can think of any thing besides their children we may find them good company.” “It is a good thing that there are so many Hens here,” said the third. “The Man throws out their grain and then we can scare them away and eat all we want of it. What fun it is to see Hens run when they are frightened!” After this short visit they went to sleep again, and so did the Man. But they went to sleep much more quickly than he did, and he was very tired and disliked being disturbed in that way. He had just fallen asleep when one of the Guinea-Hens awakened again. “Ca-mac!” said she to the others. “Ca-mac! Ca-mac! I have thought of something to say. How do you like the idea of living on this place?” “We like it,” answered the Guinea-Cock and the other Guinea-Hen. Then they went on to tell why they liked it. They said that there were no children of the stone-throwing kind, no Dog, and no Cat. They had plenty of room for the long walks which they liked to take, and there were many chances to get the food which the Man threw out. When they had spoken of all these things the Guinea-Cock said: “It is decided then that we will stay here instead of running away to
- 66. another farm. This is a good enough place for any fowl. Now let us take another nap.” While they were thinking this, the Man was thinking something quite different. In the morning while the Guinea-fowls were eating grain which had been strewn in one of the yards, the Man closed the gate, and, helped by the Little Girls, drove the three Guinea-fowls into a corner and caught them. Then he put them into the crate in which they had come, and took them across the road to the Farmer who lived there. When this was done there were many happy people left behind on the poultry-farm. The Little Girls were happy, because they had found four feathers which the Guinea-fowls lost in trying to get away from the Man. The Hens were happy, because they could now be more sure of eating the food which they found. The other poultry were glad to think that they would not have to listen to new-comers saying such dreadful things about them, and perhaps the Man, when he came back, was the happiest of all. “I gave them to the Farmer over there,” he said, “and he will give them to a poor family far away. I have stopped keeping Guinea-fowls to scare away the Crows. I would rather keep Crows to scare away the Guinea-fowls, but I think we can get along very comfortably without either.” And the poultry thought so too.
- 68. T THE GEESE AND THE BABY HE Little Girls had gone to play with a new friend who lived down the road, and the Man was working in the farthest field of the farm. The Baby had been laid in the crib for his afternoon nap, and his mother went up-stairs to work at her house-cleaning. She thought that she might possibly finish two closets if the baby did not awaken and call her too soon. She felt sure that she would know when he awakened, because she left the staircase door ajar, and he usually cried a little as soon as he got his eyes open. This time, however, the Baby slept only a few minutes and did not cry at all. He had grown a great deal since he came to live on the farm, and was becoming very strong and independent. When he opened his eyes he made no sound, but lay there quietly staring at the ceiling until he heard one of the Cocks crowing outside. He had always wanted to catch that tallest Cock and hug him—he looked so soft and warm—and now was the time to try it. When his mother was around she sometimes held his dress or one of the shoulder- straps of his little overalls and would not let him catch the Cock. He would crawl out of his crib alone and go out very quietly to try it. The Baby pulled himself up by the rounds of his crib, and tumbled over its railing onto his mother’s bed, which stood beside it. From that he slid to the floor. It took him only two minutes more to get out of the side door and down the steps. It did not take at all long for the steps, because he fell more than half the distance. If he had not been running away, or if there had been anybody around to pity him, he would have cried, but to cry now might spoil all his fun, so he picked himself up without making a sound and started for the Shanghai Cock.
- 69. The Shanghai Cock was on the ground when the Baby began toddling toward him. As the Baby came nearer he began to walk off. “I don’t want to be caught,” said he. “It is bad enough to have grown people catch me, but it would be worse to have a Baby do so, for he might choke me.” “Here, pitty Chickie!” said the Baby. “Baby want oo.” Then he tried to run, and fell down instead. The Barred Plymouth Rock Hen looked at him pityingly. “Just the way my Chickens used to act when trying to catch a Grasshopper,” said she. “It is so hard for children to learn that they cannot have everything they want.” When the Baby tumbled, the Shanghai Cock stood still, and even picked up a couple of mouthfuls of food. When the Baby got up again, the Shanghai Cock moved on. At last the Cock decided to put a stop to this sort of game, in which the Baby seemed to be having all the fun, so he flew to the top of the pasture fence and crowed as loudly as he could. The Baby’s mother heard him as she worked busily upstairs. “How loudly that Cock does crow!” said she. “I am glad that such noises do not wake the Baby. He is having a fine nap to-day.” Then she unrolled another bundle of pieces and paid no more attention to the crowing. When the Baby saw that he could not reach the Cock, he thought he would try for some of the other fowls. The Gobbler came in sight just then and he started after him. Luckily he had no red on, or it might have been the Gobbler who did the chasing. “Here, pitty Chickie!” said the Baby. “Tum, pitty Chickie! Tum to Baby.” It was the first time the Gobbler had ever been been called a “pitty Chickie,” but that made no difference. He did not want to be petted and he did not want to be caught. Baby might open and shut his tiny fat hands as many times as he pleased, beckoning to him. The Gobbler would not come. “Gobble-gobble-gobble!” said he. “Nobody
- 70. can catch me in daylight, not even with corn; and surely nobody can catch me without it.” Then he strutted slowly away. The Baby followed, but when the Gobbler pretended to lose his temper, stood all his feathers on end, spread his fine tail, dragged his wings on the ground, and puffed, the Baby turned and ran away as fast as he could. Brown Bess was no longer in the pasture, and the gate stood open. It was through this gate that the Baby ran, not stopping until he came within sight of the river along the lower edge of the pasture. The water looked so bright and beautiful that he thought he would go farther still. Perhaps he could even catch some of the Ducks and Geese that were swimming there. He had seen his sisters wade in the edge of the river one day, while his father was mending a fence near by. He would wade, too. You see Baby was only two years old, and did not understand that rivers are very dangerous places for children to visit alone, and worst of all for Babies who toddle and tumble along. He did not know that if he should tumble in that beautiful shining water he might never be able to get up again, or that if he should chase one of the Ducks too far out, he could not turn around and come back to the shore. These things he was not old enough to know. He did know that when he came into the pasture with his father or mother and went toward the river’s edge, he was always told, “No-no!” This he remembered, but that made it seem all the more fun to go there when there was nobody by to say it. The Baby stood on a little knoll near the water. “Here, pitty Chickie!” he said. “Tum to Baby, pitty Chickie!” The Ducks paid no attention to him, unless it were to swim farther from shore and keep their heads turned slightly toward him, watching to see what he was about. With the Geese, however, it was different. Geese do not like anything strange, and if they cannot understand a thing they think that there is certainly something wrong. As there is
- 71. much which they do not understand, the Geese are often greatly excited over very simple and harmless things, hissing loudly at those who are strangers to them. Now they could not understand why the Baby should stand on the river-bank and talk to them. “S-s-s-s-s!” said the Gander. “There must be something wrong about this. Let us get out of the water to see.” He scrambled up onto the bank, with his wife and the other Geese following closely behind him. He was a very stately fellow, and looked as though he could win in almost any fight. The Geese were stately too, but their legs and neck did not look so strong as his, and they let him go ahead and speak first. The Gander marched toward the Baby and stood between him and the river. “S-s-s-s-s!” said he. “What are you doing here?” “Here, pitty Chickie!” said the Baby. “Tum to Baby.” “I cannot understand you,” said the Gander, severely. “Children should speak so that they can be understood. I can always understand my own children.” He was very proud of the brood of Goslings which he and his wife had hatched. Perhaps he was even more fond of them because he had done almost as much for them as she, sitting on the eggs part of the time and standing beside her while she was sitting on them. Ganders are excellent fathers. “Go way, pitty Chickie!” said the Baby. “Baby goin’ in de watty.” “S-s-s-s-s!” said the Gander, and this time his wife hissed also. “Go back to the place where you belong. This place is for web-footed people. I have seen your feet uncovered, and you have no webs whatever between your toes. You do not belong here. Go away!” The Baby did not go away, for he was having a lovely time. The Gander did not come any nearer to him or act as though he meant to peck him, so he just laughed and waved his hands. “Why don’t you go?” asked the Geese. “The Gander told you to go away, and you should mind the Gander. We always mind him, and so should you.”
- 72. Still the Gander and the Geese did not come nearer to him, and still the Baby was not afraid. “S-s-s-s-s!” repeated the Gander. “We do not want you to swim in our river. Your body is not the right shape for swimming with Geese and Ducks. Your neck is not long enough for feeding in the river. You could never get your mouth down to the river-bottom for food without going way under. Go away! You will get wet if you go into the water. I feel quite sure that you will, for you have not nicely oiled feathers like ours. You will try to catch our children and will make us much trouble. Go away!” Just then the Baby’s mother called from the door of the house. She had come downstairs and found the Baby gone. “Baby!” said she. “Baby! Where are you?” Baby did not answer, but he turned to look at her. “S-s-s-s-s!” said the Gander and the Geese together. “S-s-s-s-s! S-s-s-s-s!” Then they walked straight for him, and the Baby started home at last. His mother heard and ran toward him in time to see it all. She understood, too, that if it had not been for the Gander and the Geese, her Baby would have gone into the river. That was why she looked so gratefully at them when she reached him and picked him up in her arms to hug and kiss.
- 73. “S-S-S-S-S!” REPEATED THE GANDER. Page 166 Perhaps it was because she had been so frightened that she had to sit right down on a little hillock and rest. The Gander and the Geese stood around and wondered why she made such a fuss over the Baby. “He is nothing remarkable,” they said to each other. “He certainly could not swim if he had a chance, and we saw how often
- 74. he fell down when he tried to run. Why does she put her mouth up against his in that way? There is simply no understanding the actions of people who live in houses.” There was one sort of action which they could understand very well indeed. The Little Girls came home just then and their mother had them bring oats from the barn to scatter on the river. Then the Gander, with his wife and the other Geese, gladly went back to the river to feed, for there is nothing which pleases Geese better than to eat oats that are floating on the water.
- 76. W THE FOWLS HAVE A JOKE PLAYED ON THEM HEN the Man first bought the farm and came to live there, he could not understand a thing that his poultry said. This made it very hard for him, and was something which he could not learn from his books and papers. You remember how the Little Girls understood, better than he, what the Cocks meant by crowing so joyfully one day. It is often true that children who think much about such things and listen carefully come to know what fowls mean when they talk. The Man was really a very clever one, much more clever than the Farmer who had lived there before him, and he decided that since he was to spend much of his time among poultry, he would learn to understand what they were saying. He began to listen very carefully and to notice what they did when they made certain sounds. It is quite surprising how much people can learn by using their eyes and ears carefully, and without asking questions, too. That was why, before the summer was over, the Man could tell quite correctly, whenever a fowl spoke, whether he was hungry or happy or angry or scared. Not only these, but many other things he could tell by carefully listening. He could not understand a Hen in exactly the way in which her Chickens understand her, but he understood well enough to help him very much in his work. Then he tried talking the poultry language. That was much harder, yet he kept on trying, for he was not the sort of Man to give up just because the task was hard. He had been a teacher for many years, and he knew how much can be done by studying hard and sticking to it. The Man was very full of fun, too, since he had grown so strong and fat on the farm. He dearly loved a joke, and was getting ready to
- 77. play a very big joke on some of his poultry. Anybody who has ever kept Hens knows how hard it is to drive them into the poultry-house when they do not wish to go. People often run until they are quite out of breath and red in the face, trying to make even one Hen go where she should. Sometimes they throw stones, and this is very bad for the Hens, for even if they are not hit, they are frightened, and then the eggs which they lay are not so good. Sometimes, too, the people who are trying to drive Hens lose their temper, and this is one of the very worst things that could happen. The poultry had not paid much attention to the Man when he was learning their language. They were usually too busy talking to each other to listen to what he was saying. Once the Shanghai Cock said what he thought of it, however: “Just hear him!” he had said. “Hear that Man trying to crow! He does it about as well as a Hen would.” You know a Hen tries to crow once in a while, and then the Cocks all poke fun at her, because she never succeeds well. All this happened before the Man had been long on the farm, and before the Shanghai Cock had learned to like him. The Shanghai Cock would have been very much surprised if anybody had then told him that he would ever be unable to tell the Man’s voice from that of one of his best friends. Throughout the summer the fowls who had always lived on the farm were allowed to run wherever they wished during the day, and were not driven into the pen at night. There was always some corn scattered in their own yard for them just before roosting-time, and they were glad enough to stroll in and get it. When they finished eating they were sure to find the outer gate closed, and then they went inside the pen to roost. Now, however, the days were growing much shorter and the nights cooler, and a Skunk had begun prowling around after dark. The Man decided that if he wanted to keep his poultry safe, he must have them in the pens quite early and shut all the openings through which a night-hunting animal might enter to
- 78. catch them. He liked to attend to this before he ate his own supper, and the poultry did not wish to go to roost quite so early. They often talked of it as they ate their supper in the yard. “I think,” said the Brown Hen, “that something should be done to stop the Man’s driving us into the pen before we are ready to go. It is very annoying.” “Annoying?” said the White Cock, who was a great friend of hers. “I should say it is annoying! I hadn’t half eaten my supper last night when I heard him saying, ‘Shoo! Shoo!’ and saw him and the Little Girls getting ready to drive us in.” “Well, you might better eat a little faster the next time,” said the Black Hen. “I saw you fooling around when you might have been eating, and then you grumbled because you hadn’t time to finish your supper.” “I would rather fool around a little than to choke on a big mouthful, the way you did,” replied the White Cock, who did not often begin a quarrel, but was always ready to keep it up. “I was hungry all night,” he added. “It is so senseless,” said the Brown Hen. “He might just as well drive us in after we have had time enough for our supper, or even wait until we go in without driving. I have made up my mind not to go to- night until I am ready.” “What if they try to drive you?” asked the White Cock. “I will run this way and that, and flutter and squawk as hard as I can,” replied the Brown Hen. The Black Hen laughed in her cackling way. “I will do the same,” said she. “It will serve the Man right for trying to send us to roost so early. I think he will find it pretty hard work.” The White Cock would make no promises. He wanted to see the Hens run away from the Man, but thought he would rather stand
- 79. quietly in a corner than to flutter around. He was afraid of acting like a Hen if he made too much fuss, and no Cock wishes to act like a Hen. The Shanghai Cock felt in the same way. “I am too big for running to and fro,” said he, “but I will keep out of the pen and watch the fun.” He had hardly spoken these words when the Man and the Little Girls came into the yard and closed the gate behind them. The poultry kept on eating, but watched them as they ate. Suddenly the Brown Hen picked up a small boiled potato that she had found among the other food, and ran with it in her bill to the farthest corner of the yard. The Black Hen ran after her and the other Hens after them. The Cocks remained behind and watched. The Man and the Little Girls tried to get between the Hens and the farthest side of the fence. The Hens would not let them for a while, but kept running back and forth there, until the potato had fallen to pieces and been trampled on without any one having a taste. When the Man and the Little Girls finally got behind the Hens, the Little Girls spread out their skirts and flapped them and the Man said, “Shoo! Shoo!” Then the Hens acted dreadfully frightened, and the Cocks began to turn their heads quickly from side to side, quite as though they were looking for a chance to get away. They were really having a great deal of fun. Whenever the Man thought that he had them all ready to go into the open door of the pen, one of the Hens would turn with a frightened squawk and flutter wildly past him again to the back end of the yard, and then the Man would have to begin all over. Several of the Hens dropped loose feathers, and it was very exciting. “Well,” said the Shanghai Cock, as the Man went back the fifth time for a new start, “I think that Man will leave us alone after to-night.” “Yes,” said the White Cock, who was standing near him, “I think we are teaching him a lesson.”
- 80. He spoke quite as though he and the other Cock were doing it, instead of just standing by and watching the Hens. But that is often the way with Cocks. After the Man had tried once more and failed, he certainly acted as though he was ready to give up the task. He walked to the back end of the yard, took off his hat, and wiped his forehead with his handkerchief. The Little Girls stood beside him, and he picked up a feather to show them. It was a wing-feather, and he was showing them how the tiny hooks on each soft barb caught into those on the next and held it firmly. The poultry watched him for a while and then began eating once more. They thought him quite discouraged. The Shanghai Cock and the White Cock were standing far apart when somebody called “Er-ru-u-u-u-u!” which is the danger signal. As soon as he heard it, each Cock thought that the other had spoken, and opened his bill and said, “Er-ru-u-u-u-u!” in the same tone, even before he looked around for a Hawk or an Eagle. Every Hen in the yard ducked her head and ran for the door of the pen as fast as her legs would carry her. The Cocks let the Hens go ahead and crowd through the doorway as well as they could, but they followed closely behind. They were hardly inside when the door of the pen was closed after them and they heard the Man fastening it on the outside. “Wasn’t that a shame!” said the Brown Hen, who always thought that something was a shame. “We didn’t finish our supper after all!” “I know it,” said the White Cock. “It happened very badly, and all that running had made me hungry.” “What was the danger?” asked the Shanghai Cock. “I had no time to see whether it was an Eagle or a Hawk coming.” “What do you mean?” cried the White Cock. “If I had given the alarm which took all my friends from their supper into the pen, I
- 81. think I would take time to see what the danger was. Can’t you tell one kind of bird from another?” “I can if I see them,” answered the Shanghai Cock, rather angrily. “I did not see this one. I looked up as soon as you gave the cry, but I saw nothing. I repeated the cry, as Cocks always do, but I saw nothing.” “Now see here,” said the White Cock, as he lowered his head and looked the Shanghai Cock squarely in the eyes, “you stop talking in this way! You gave the first warning and you know it. I only repeated the call.” “I did not,” retorted the Shanghai Cock, as he lowered his head and ruffled his feathers. “You gave the warning and I repeated it.” “He did not,” interrupted the Brown Hen. “I stood right beside him, and I know he did not give the first call.” “Well,” said the Barred Plymouth Rock Hen, “I was standing close to the Shanghai Cock, and I know that he did not give the first call.” (Her Chickens were now so large that they did not need her, and she had begun running with her old friends.) Then arose a great chatter and quarrel in the pen. Part of the Hens thought that the White Cock gave the first warning, and part of them thought that the Shanghai Cock did. Everybody was out of patience with somebody else, and all were scolding and finding fault until they really had to stop for breath. It was when they stopped that the Speckled Hen spoke for the first time. She had never been known to quarrel, and she was good-natured now. “I believe it was the White Plymouth Rock Cock in the other yard,” said she. “Why didn’t we think of that before?” “Of course!” said all the fowls together. “It was certainly the White Plymouth Rock Cock in the other yard.” Then they laughed and spoke pleasantly to each other as they began to settle themselves
- 82. for the night. “We might as well go to roost now,” they said, “even if it is a bit early. All that running and talking was very tiring.” But it was not the White Plymouth Rock Cock who had said “Er-ru-u- u-u-u!” He and his Hens had run into their pen at the same time, and had been shut in. Only the Man and the Little Girls knew who it really was, and they never told the poultry.
- 84. L THE LITTLE GIRLS GIVE A PARTY ATE in the fall, when the Man began to talk of shutting the poultry into their own yards for the winter, there came a few mild and lovely days. The Little Girls had been playing out-of-doors in their jackets, but now they left them in the house and ran around bare-headed, as they had done during the summer. All the poultry were happy over the weather, and several said that, if they thought it would last long enough, they would like to raise late broods of Chickens. The fowls had finished moulting, and had fine coats of new feathers to keep them warm through the winter. The young Turkeys looked more and more like their mothers, for they were already nearly as large as they ever would be. The Goslings and the Ducklings had grown finely, and boasted that their legs and feet began to look rougher and more like those of the old Geese and Ducks. The Chickens were all White Plymouth Rocks this year, and the tiny red combs which showed against the snowy feathers of their heads made them very pretty. Even the Hens who had cared for them since they were hatched would not have had them any other color, although at first they had wished that their Chickens could look more like them. In the barn all was neat and well cared for. The Man had made Brownie a warm box-stall, so that he need not be tied in a cool and narrow place whenever he stood in the barn, but might turn around and take a few steps in any direction he chose. There was plenty of fine hay in the loft for him, and the place where Brown Bess and her Calf were to stand had also been made more comfortable. There were great bins filled with grain for the poultry, and another full of fine gravel for them to eat with their meals. They had no teeth and could not chew their food, you know, so they had to swallow enough
- 85. gravel, or grit, for their stomachs to use in grinding it and getting the strength out. In another place was a great pile of dust for winter dust-baths. Everything was so well prepared for cold weather that it seemed almost funny to have warm days again. And just at this time the Little Girls had a birthday. Not two birthdays, you understand, but one, for they were twins and were now exactly six years old. They were plump and rosy Little Girls, and very strong from living so much out-of-doors. Each had a new doll for a birthday gift, and the funniest part of it was that the brown-haired Little Girl had a brown- haired doll and the golden-haired Little Girl had a golden-haired doll. That made it easy to tell which doll was which, just as the difference in hair made it easy for their parents to tell one twin from the other. When they first awakened they were given birthday kisses instead of birthday spanks, six apiece for the years they had lived, a big one on which to grow, and another big one on which to be good. After the breakfast dishes were washed and put away, their mother made two birthday cakes for the Little Girls and put six candles on each. With all this done for them, one would certainly expect the Little Girls to be perfectly happy. But, what do you think? They could not be perfectly, blissfully happy, because they were not to have a party. Every year before this, as far back as they could remember, they had been allowed to have a party, and this year they could not have it, because they were living on a farm and there were no other children who could come. It is true that there were two others living quite near, but these two had the measles and could not go to parties. By the time they were over the measles, the birthday would be long past, and so the Little Girls were disappointed. It was when the brown-haired Little Girl was telling her doll about the last year’s party, and the golden-haired Little Girl’s eyes were filling with tears, that their mother had a bright idea. She would not tell them what it was, but asked them to care for the Baby while she went out to talk with the Man in the barn.
- 86. When she came back she told them that they might have a party after all and invite the poultry to come. “I think it will be great fun,” said she, “and I am sure they have never been to a birthday party in their lives.” How happy the Little Girls were then! The Man had put a very large box just in front of the poultry-yards where the White Plymouth Rocks were kept, so that, by crowding into the corners, the Chickens on one side of the separating fence and the Cock and Hens on the other could come quite near to the box. Inside the big box was another which was to be their table, and a couple of milking stools on which they were to sit. The Baby’s chair was to be brought when he came. Of course it seemed a long time to wait until afternoon, when the party was to come off. If there had not been so much to do, the Little Girls certainly could not have been patient. It was wonderful how many things their mother could suggest. In the first place, they had to write a few invitations to pin up where the fowls could see them. Then they had to go over to the edge of the woods and hunt all along the roadside to find late flowers, bits of brake, and autumn leaves, with which to trim their box and the table. After that they took pans and got grain for their guests from the bins in the barn. These they carried to the big box and placed on the table inside. It was not long afterward that the brown-haired Little Girl found the Black Hen and the White Cock eating from these pans. “Oh, shoo!” she cried, running as fast as she could toward them and flapping her skirts. “Shoo! Shoo! It isn’t time for you to come, and you mustn’t eat up the party yet.” The other twin feared that, after being frightened away in this fashion, these two fowls would not want to come at the proper time, but she need not have worried. Fowls are always glad to come to a good supper, and there is much more danger of their coming too early and staying too late than there is of their not coming at all. After that the pans of grain were carried into the house to wait until the right time.
- 87. In the afternoon the twins and their dolls came out to the big box which they pretended was their house. The open side of it was toward the poultry-yards, and there was plenty of room between for the fowls who were running free to come in and get their food. The Little Girls had wanted to put on their Sunday dresses, but their mother told them that she did not think it would be really polite to the poultry, who had to wear the very same feathers that they had on every day. So the Little Girls contented themselves with having their hair done up on top of their heads and bows of yellow tissue paper pinned on the knots. This made them feel very fine indeed, and as though being six years old were almost the same as being grown up. They had some beautiful red tissue paper which they wanted to use, but when they remembered how the Gobbler felt about red, they decided to use the yellow instead. And that was both wise and kind. One should always try to make guests happy. The Baby was not to come out until supper-time, so the Little Girls and their dolls played quite alone for a while. There was much to tell and to show the dolls, for it was the first time they had ever been on a farm, and everything must have seemed strange to them. “Do you see that tall White Plymouth Rock Cock over there?” said the brown-haired twin to hers. “My Father says he is the most vallyoobol fowl on the farm. He cost a lot of money. I asked Father if he paid as much as ten cents for him, and he said he paid a great deal more. Just think of that! More than ten cents! You must be very polite to him.” “I will show you our kindest Hen,” said the golden-haired twin to her doll. “She is coming this way now. She is the Barred Plymouth Rock Hen, and she is a peticullar friend of my Father’s. She didn’t cost so much as some of the others, but she is very good.” “And there comes the Speckled Hen,” said the brown-haired twin. “She doesn’t lay many eggs, but my Father says that she is the best Hen on the farm about taking care of lonely or sick Chickens. She is very small, but she spreads herself out so she can cover a lot, and
- 88. then she cuddles them until they are happy again, and can run around with her and eat the Worms she scratches up for them.” There is no telling how much more the dolls might have learned about their new neighbors, if the Baby and the mother of the Little Girls had not come out just then. The Baby was put in his chair in the big box and given a cracker to eat, while the Little Girls stood outside and called to their company. “Come, Chick, Chick, Chick!” they called. “Come, Chick, Chick, Chick!” From far and near the Hens came running, with lowered heads and hurrying feet, to seize the food which they knew would be given them after that call. The Shanghai Cock and the White Cock followed more slowly, as was their habit. The Gander waddled gravely along from the farthest corner of the pasture in which the poultry-house stood, with his wife and the other Geese following solemnly behind him. The Turkeys, all together once more since the children were so large, came with rather more haste from the roadside, where they had been hunting acorns. And down by the river the Ducks and their children could be seen scrambling up onto the bank and shaking themselves. All were glad enough to come to the party as soon as they were sure it was time, but whether they had understood the invitations which had been pinned around for them to read—well, who can tell about that? The Man came from the barn to see the fun, and he and the Woman set the two birthday cakes from her basket onto the table. After she had done that, she had to pay more attention to the Baby, who kept trying to reach them with his fat little hands. The Man handed a pan of corn to each of the Little Girls. “Wait until the Ducks get here,” he said. “They must have their share and there is plenty of time.” The brown-haired Little Girl felt that those who were waiting should be amused in some way, so she began to talk to them. “This is our birthday party,” she said, “and we are very glad you didn’t have the
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