Criteria Air Pollutants and Ambient Air Monitoring
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The document discusses criteria air pollutants monitored by the EPA, particularly focusing on ozone, its sources, chemistry, and standards for ambient air quality. It outlines the principles of air monitoring, including the instrumentation and data analysis methods used for various pollutants, along with meteorological considerations. Additionally, it highlights the importance of quality assurance in data collection and the regulatory framework surrounding hazardous air pollutants.
Criteria Air Pollutants and Ambient Air Monitoring
- 1. Criteria Air Pollutants and Ambient Air Monitoring Topics for Discussion • Air pollutants regulated by the EPA • Ozone – sources, chemistry, standard, sampling, air monitor works • Instrumentation • Meteorology • How data is collected/stored • Locating a monitor • Documentation/Analysis of data 1
- 2. Criteria Pollutants • • • • • • • • • Ozone Carbon Monoxide http://www.epa.gov/airquality/carbonmonoxide/pdfs/COFactShe etAugust12v4.pdf Lead Nitrogen Oxides (NO, NO2) Particulate Matter (PM10)/Particulate Matter (PM2.5) Sulfur Oxides Reference: http://www.epa.gov/air/criteria.html Note: covered under 40CFR part 50 National Ambient Air Quality Standards (NAAQS) 2
- 3. Brief comment: Ozone • Stratospheric ozone protects us from the UV rays of the sun. • Ground level ozone at high concentrations can irritate the respiratory tract and damage plant life in high concentrations. How is O3 created? 3
- 4. Chemistry of Ozone VOCs + NOx + Sunlight + Heat = Ozone Night Time O3 Chemistry 4
- 5. Ambient Air Standard-Ozone • • To attain the ozone NAAQS, the 3-year average of the annual 4thhighest daily maximum 8-hour ozone concentration must be less than or equal to 0.075 PPM (or 75 ppb). The old ozone threshold value for a 1-hour standard is 0.12 parts per million (PPM), measured as a 1-hour average concentration. http://www.epa.gov/airquality/ozonepollution/ OSHA: https://www.osha.gov/dts/sltc/methods/inorganic/id214/id214.html 8 Hour Average DATE 8-Hour Average 03/02/2011 80 04/15/2011 90 09/03/2011 75 09/16/2011 100 XX/XX/2010 90 4th Highest 8-hr XX/XX/2009 100 4th Highest 8-hr The 4th highest 8-hour average is: 75 This would average to 88 5
- 6. Schematic Diagram Ozone Monitor Air Pump Thermistor Hg Lamp 254nm Absorption Cell Photodiode Pressure Sensor Solenoid Valve Ozone Scrubber Air Inlet Ozone Monitors Rack mount with ozone transfer standard instrument and ozone monitor. 6
- 7. Instruments for other Pollutants • Criteria pollutants: Ozone, SO2, NOx, CO • Other pollutants: NH3, H2S, CO2, NOy, Total Hydrocarbon • VOC (volatile organic compounds) • Laser/IR systems also used. Air Monitor – Basic Principles • Chemiluminescence • UV flourescence • Beer’s law 7
- 8. Chemiluminescence The chemiluminescence reaction of NO to NO2: NO + O3 ==> NO2+ O2 + hv http://www.k2bw.com/chemiluminescence.htm Variations of chemiluminescence have been used to perfom measurements of Ammonia (NH3): NH3 + O2 ==> NO + H2O or: 4NH3 + 5O2 = 4NO + 6H2O then: 4NO + 4O3 -------->4NO2+4O2 + 4hv Schematic of a reaction chamber under vacuum and a Photomultiplier tube (PMT) for detection. Principle - UV fluorescence Principle - UV fluorescence The UV fluorescence method operates on the principle that when the SO2 molecules contained in the sample gas are excited by ultraviolet radiation they emit a characteristic fluorescence in the range of 220- 240 nm. This fluorescence is measured and the SO2 concentration is obtained from changes in the intensity of the fluorescence. The reactive mechanism is: (1)SO2 + hv1 ¤ SO2* (2)SO2* ¤SO + (O) (3)SO2* ¤ SO2 + hv2 (4)SO2*+ M ¤ SO2 + M Here, (1) shows the excited state of the SO2 molecules that have absorbed the amount of energy hv1 by ultraviolet radiation. (2) shows the amount of energy, hv2 emitted by the excited molecules as they return to the ground state. (3) shows the decomposition by the light emitted from the excited molecules. (4) shows the quenching, i.e., the energy lost by the excited molecules colliding with other molecules. http://www.horiba.co.uk/apsa360.htm 8
- 9. Beer’s Law Many compounds absorb ultraviolet (UV) or visible (Vis.) light. The diagram below shows a beam of monochromatic radiation of radiant power P0, directed at a sample solution. Absorption takes place and the beam of radiation leaving the sample has radiant power P. The amount of radiation absorbed may be measured in a number of ways: Transmittance, T = P / P0 % Transmittance, %T = 100 T Absorbance, A = log10 P0 / P A = log10 1 / T A = log10 100 / %T A = 2 - log10 %T http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/beers1.htm Calibration-Ozone 9
- 10. Calibration-NOx Calibration of a NOx Monitor. Zero Air machine, NOx, Multigas calibrator. Y = mx + b Find the calibration curve, use this to calculate final value for air pollutant. 10
- 11. TEOM 1400 Ambient PM Sampler 11
- 12. Meteorological Parameters • • • • Wind Speed/Wind Direction Air Temperature/Relative Humidity Solar Radiation Ultra-Violet Ultra-Violet • UV-A radiation refers to atmospheric radiation from 320 nm-400 nm (that's 0.320-0.400 m m). UV-A is very important to photosynthesis and plant studies. • UV-B is the shortest wavelength atmospheric radiation that actually reaches the ground, and covers from 280-320 nm (that's 0.280-0.320 nm). However, it is UV-B that causes skin cancer over prolonged exposure. • UV-C is "extraterrestrial" solar radiation, and includes light with wavelengths between 100-280 nm. • Reference: http://www.yesinc.com/products/data/FAQuvrad/faq4.html 12
- 13. Zeno Datalogger Documentation • Quality Assurance Project Plan (QAPP) – Calibration of instrumentation, how data is processed and stored • Site Operations Procedures (SOP) – Calibration of instruments – How to troubleshoot equipment – Setting up a site • Logbook for each site • Logbook for each instrument • Atmospheric Research & Analysis Inc.: http://www.atmospheric-research.com/newindex.html 13
- 14. Air Monitoring Sites-Texas Typical Site 14
- 15. TCEQ Sites for Ambient Air Monitoring Ozone Precursors/Air Toxics Air Toxics - There are currently 188 hazardous air pollutants (HAPS), or air toxics, regulated under the Clean Air Act (CAA) that have been associated with a wide variety of adverse health effects. A subset of the 188 toxics thought to have the greatest impact on the public and the environment in urban areas has been identified as the Urban Air Toxics Strategy compounds of interest. This subset of 33 compounds includes volatile organics, semivolatile organics, and metals. Two of the six compounds identified as the risk drivers in the strategy, benzene and 1,3-butadiene, are volatile organics which are amenable to AutoGC analysis. Data for these two target compounds as well as all other target compounds from this analysis are forwarded to TCEQ Toxicology Section to identify any potential health impacts that might be associated with exposure to the measured concentrations. Ref: http://www.tceq.texas.gov/airquality/monops/agc/agc_support.html#why 15
- 16. GC-MS Analytical System Sample Canister Mass Spectrometer Gas Chromatograph Pre-concentrator ANALYSIS AND COLLECTION OF DATA 16
- 17. Automated Data Collection Databases • • • • • The first source is the state. http://www.tceq.texas.gov/agency/air_main.html EPA keeps an extensive database of monitoring sites. http://www.epa.gov/ttn/airs/airsaqs/ Free data available for meteorology, terrain. NOAA, NASA, many others. • http://www.webmet.com/ 17
- 18. Ozone Concentrations vs Wind Time Series Graph September 29, 2004 120 80 60 40 20 23 21 19 17 15 13 11 9 7 5 3 0 1 Ozone-ppb 100 Time AP HR VI CAMS04 CAMS21 Kingsville 18
- 19. Statistics • Average, median, frequency analysis. • Box-whisker plots. • Trend analysis. Wind Rose • Reference: http://www.questconsult.com/papers/weather-variations-qra/ 19
- 20. Pollution Rose • Can be used for evaluating the common direction of pollutants • Useful for ozone, PM, SO2, VOCs. Direction of Sources • • • • Non parametric regression Positive Matrix Factorization Conditional Probability Function Can be used for: – Particulate Matter – VOC’s • Not appropriate for ozone 20
- 21. Air Parcel Trajectories REFERENCES • • • • • Criteria Pollutants: http://www.epa.gov/air/criteria.html Air Monitoring SOP’s: http://www.atmospheric-research.com/ Zeno Datalogger Manual Quality Assurance Handbook for Air Pollution Measurement Systems Volume II Ambient Air Quality Monitoring Program http://www.epa.gov/ttnamti1/files/ambient/pm25/qa/QA-HandbookVol-II.pdf 21