Modified territreal environment by Muhammad Fahad Ansari 12IEEM14
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The document discusses the terrestrial environment, including the surface soil, vadose zone, and saturated zone below the surface. It describes how soil is composed of minerals, pore space, and small amounts of organic matter. The texture of a soil, defined by mineral particle sizes, influences properties like pore size distribution and water movement. Microbes are also discussed in relation to soil conditions like moisture availability and pore sizes that impact their movement.
Modified territreal environment by Muhammad Fahad Ansari 12IEEM14
- 1. Terrestrial Environment Muhammad Fahad Ansari 12IEEM14
- 2. surface soil, the vadose zone, and the saturated zone
- 3. Spontaneous water movement Saturated zone Capillary fringe (nearly saturated) Vadose zone (unsaturated) Surface soil (unsaturated) Scale can range from 10 to 100’s of meters Water table X Surface soils Vadose zone Saturated zone shallow aquifers intermediate aquifers deep aquifers
- 4. 1) 45% mineral (Si, Fe, Al, Ca, K, Mg, Na) The two most abundant elements in the earth’s crust are Si (47%) and O (27%) Quartz = SiO2 Clay minerals are aluminum silicates Nonsilicates = NaCl, CaSO4 (gypsum), CaCO3 (calcite) Pore space Mineral OM Components of a typical soil 2) 50% pore space 3) 1 to 5% organic matter
- 5. Soil texture – this defines the mineral particle sizes that make up a particular soil. particle diameter Surface to volume ratio range (mm) (cm2/g) Sand: 0.05 – 2 mm 50 Silt: 0.002 – 0.05 mm 450 Clay: 0.0002 – 0.002 mm 10,000
- 6. Pore size distribution is important when one considers movement of fluids and of microbes through a porous medium. Protozoa and bacteria will have difficulty moving through even sandy porous media. Similarly fluids like water move more easily through large pores, not because the water molecules are too large, but because there is less resistance to water movement through larger spaces. Fine Coarse Number of pores Fine Coarse Number of pores Fine Coarse Number of pores Clay texture Loam texture Sand texture The amount of clay and organic matter in a soil influence the reactivity of that soil because they both add surface area and charge. Because large amounts of clay make the texture of the soil much finer, the average pore size is smaller. Texture and pore size distribution
- 7. Filtration is important when the size of the bacterium is greater than 5% of the mean diameter of the soil particles 20 um 0.6-20 um 0.02–0.6 um Pore size 5% of the mean pore diameter
- 8. Water movement and soil water potential Soil water potential depends on how tightly water is held to a soil surface. This in turn depends on how much water is present. Surface forces have water potentials ranging from – 10,000 to –31 atm. Capillary forces have water potentials ranging from –31 to –0.1 atm. Optimal microbial activity occurs at approximately -0.1 atm. At greater distances there is little force holding water to the surface. This is considered free water and moves downward due to the force of gravity. Soil air FREE WATER Gravitational forces Capillary forces Surface forces Soil particles % Saturation of the soil pore 100% 0% A m Soil air Increasing distance from particle surface Soil air FREE WATER Gravitational forces Capillary forces Surface forces Soil particles % Saturation of the soil pore 100% 0% A m Soil air Increasing distance from particle surface Soil air FREE WATER Gravitational forces Capillary forces Surface forces Soil particles % Saturation of the soil pore 100% 0% A m Soil air Increasing distance from particle surface Soil air FREE WATER Gravitational forces Capillary forces Surface forces Soil particles % Saturation of the soil pore 100% 0% A m Soil air Increasing distance from particle surface
- 9. Soil atmosphere The composition of the earth’s atmosphere is approximately 79% nitrogen, 21% oxygen, and 0.03% carbon dioxide. Microbial activity in the soil can change the local concentration of these gases especially in saturated areas. 0.03 0.3 – 3 Up to 10 20.9 18 - 20.5 0 - 10 78.1 78.1 >79 Atmosphere Well-aerated surface soil Fine clay/saturated soil Carbon Dioxide (CO2) Oxygen (O2) Nitrogen (N2) Location Composition (% volume basis)
- 10. Microorganisms in soil – an overview • minor role as primary producers • major role in cycling of nutrients • role in soil formation • role in pollution abatement
- 11. Bacteria Culturable counts 106 – 108 CFU/g soil Direct counts 107 – 1010 cells/g soil Estimated to be up to 10,000 species of bacteria/g soil Actinomycetes Culturable counts 106 – 107 CFU/g soil Gram Positive with high G+C content Produce geosmin (earthy smell) and antibiotics Fungi Culturable counts 105 – 106/g soil Obligate aerobes Produce extensive mycelia (filaments) that can cover large areas. Mycorrhizae are associated with plant roots. White rot fungus, Phanerochaete chrysosporium is known for its ability to degrade contaminants. Highest numbers Highest biomass Numbers and types of microbes in typical surface soils
- 12. Comparison of bacteria, actinomycetes, and fungi Bacteria Actinomycetes Fungi Numbers highest intermediate lowest Biomass --- similar biomass --- largest Cell wall --- PEP, teichoic acid, LPS --- chitin/cellulose Competitiveness most least intermediate for simple organics Fix N2 Yes Yes No Aerobic/Anaerobic both mostly aerobic aerobic Moisture stress least tolerant intermediate most tolerant Optimum pH 6-8 6-8 6-7 Competitive pH 6-8 >8 <5 Competitiveness all soils dominate dry, dominate high pH soils low pH soils
- 13. The Aquatic Environment Outline: – Water cycle – Properties of water – Light and temperature in aquatic environments – Oxygen and carbon dioxide in water – Water movement in streams – Tides and estuaries
- 14. Water or hydrologic cycle
- 15. Water storages and fluxes
- 16. •High specific heat: •Specific heat: number of calories necessary to raise 1 gram of water 1 degree Celsius •Peculiar density-temperature relationship: pure water most dense when at 4 degrees Celsius. Physical properties of water
- 17. Physical conditions in the aquatic environment – Light –Temperature –Oxygen –Salinity –Acidity
- 18. Physical conditions: 1. Light • Some incident sunlight is reflected from the water’s surface • The lower the angle of the sun, the greater the reflectance The amount of light that penetrates the water’s surface varies with latitude, season • Light that does penetrate is absorbed by water molecules…
- 19. Fig. 4.6
- 20. • Different wavelengths penetrate to different depths • E.g. for visible light: – Red: most rapidly absorbed – Blue: least rapidly absorbed --> greatest penetration • Suspended particles in the water also absorb and scatter light --> reduces penetration even further
- 21. Physical conditions 2. Temperature • Water is most dense at 4oC • Lake in summer: – temperature drops with increasing depth – Stratification of water column •Epilimnion: warm surface water •Thermocline: rapid decline in temperature •Hypolimnion: cold, dense water (~4oC)
- 23. Temperature • Tropical lakes: thermocline all year • Temperate lakes: only in summer – Autumn: surface cools --> temperature becomes uniform throughout (~4oC) Mixing of all parts = fall turnover – Increased nutrient levels at the surface
- 24. Fig. 4.7
- 25. Temperature • Temperate lakes in winter – surface colder than 4oC – Bottom near 4oC • Temperate lakes in spring – Ice melts --> surface warms --> ~4oC throughout Spring turnover
- 26. Temperature • Oceans: never undergo complete turnover • Winter: thermocline rises • Summer: thermocline descends Bottom never mixes with top
- 27. Temperature • Flowing waters: temperature variable • Shallow waters: follow air temperature – Track changes slowly
- 29. Physical conditions: 3. Oxygen • Diffuses from air through surface • Solubility decreases as water temperature increases • Solubility decreases as salinity increases • Diffusion: 10,000 times slower than in air Mixing of water by winds and currents is critical • Temperature stratification --> oxygen stratification
- 31. Oxygen Oceans: Highest conc. near surface (upper 10- 20m) – Photosynthesis – Wind mixing • Decreases to minimum at 500-1,000 m – Oxygen minimum zone – No turnover --> water never reoxygenated • Below 1,000 m : conc. increases again – Polar regions: surface (high conc.) waters cool, sink --> currents --> highly oxygenated deep waters carried to lower latitudes
- 33. Physical conditions: 4. Salinity • Flow of rivers into ocean: dissolved materials increase over time • Concentrations can’t increase beyond maximum solubility limit. – e.g. Ca2+ forms CaCO3 (limestone) – e.g. Cl- - highly soluble (max. 360 g/L) • Maximum not yet reached (today 19 g/L) • Total concentration of all salt in ocean: 3.5% or 35 ppt • Fresh water 0.065 to 0.3 ppt
- 36. Factors affecting pH • Fresh water: underlying rock is important – Limestone: • raises pH • buffers against changes – Sandstone, granite • Lowers pH • Oceans: Na+, K+, Ca2+ raise pH – pH ~ 7.5-8.4
- 37. Effect of pH on living organisms • Direct effects: interference with physiological processes • Indirect effects: effect on other dissolved substances – E.g. Al3+: concentration increases below pH 5 • Insoluble at higher pH
- 38. Water Movement Fast flow --> rocky bottom Slow flow --> silty bottom Increase in water volume increase flow rate
- 39. The Terrestrial Environment Outline: • Life on land • Light and vegetation • Soils – formation – horizons – moisture holding capacity – ion exchange Readings: Ch. 5
- 40. …is a hostile environment • Living cells 75-95% water; must remain hydrated to survive • Water availability fluctuates with precipitation patterns Constraints: 1. Desiccation • Terrestrial organisms have adaptations that reduce water loss, and/or replace lost water
- 41. 2. Structural support • Trees invest > 80% of their mass in supportive woody tissue • Animals: skeletons
- 42. Terrestrial env’t - constraints 3. Temperature variations on land >> those in the water
- 43. Physical conditions 1. Light availability
- 44. Leaf area index
- 46. Daily distribution of light
- 47. Seasonal distribution of light
- 48. Soil 1. Formation • Begins with weathering of rocks • Types of weathering: i. Mechanical --> breakup • Freezing / thawing • Erosion • Roots ii. Chemical • Oxidation • Acids • Rainwater acts as medium for reactions
- 49. Factors affecting soil formation I. Parent material • Bedrock, glacial till, eolian (wind-deposited), fluvial (water-deposited) II. Biotic factors • Roots – Increase mechanical weathering – Reduce erosion – Reduce leaching – Increase organic material (affects pH)
- 50. Factors affecting soil formation III. Climate • Direct effects: temperature, winds, pptn • Leaching = movement of solutes • Indirect effects: via plant growth IV. Topography • Steep slope --> increased erosion, “soil creep” V. Time • From bedrock to soil: ~ 2,000-20,000 yrs
- 51. 2. Soil types • Colour reflects chemical composition – Black: high organic matter – Yellow-brown or red: Fe oxides – Dark purple: Mn oxides – White / gray: CaCO3, MgCO3, quartz, gypsum
- 52. Soil types • Texture reflects particle size – Components of soil: • Sand: 0.05 - 2.0 mm • Silt: 0.002 - 0.05 mm • Clay: < 0.002 mm
- 53. “Texture” = %, by weight, of sand, silt and clay Size: 0.002 - 0.05 mm Size: 0.05 - 2.0 mm Size: < 0.002 mm
- 54. Soil texture • Affects pore space --> air, water movement • Coarse texture (high sand, low clay): – Large pores – Rapid water infiltration, drainage • Fine texture (low sand, high clay): – Small pores – Poor aeration – High surface area – High compactability
- 57. Moisture retention • When all the pore spaces between soil particles are completely filled with water, the soil is at field capacity • Clay soil: – small pores --> slow drainage – Total pore space actually > than sandy soil! (higher field capacity) • Capillary water = water held by capillary action – Difficulty of extraction increases as moisture content decreases – wilting point: no further extraction
- 58. Available water capacity (AWC) = field capacity - wilting point • Pure sand: 30-40% of volume = pores • Pure clay: up to 60% of volume = pores – Higher field capacity and higher wilting point • AWC highest in soils of intermediate texture (loams)
- 59. Ion exchange capacity = total # of charged sites on soil particles within a volume of soil Al3+ > H+ > Ca2+ > Mg2+ > K+ = NH4 + > Na+ Ion exchange capacity