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Regional Air Pollution Study

Regional Air Pollution Study. Alissa Dickerson, M.S. Environmental Specialist Enviroscientists, Inc. Goal of Study. Western Regional Air Partnership (WRAP) http://wrapair.org C auses o f H aze A ssessment (COHA)

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Regional Air Pollution Study

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  1. Regional Air Pollution Study Alissa Dickerson, M.S. Environmental Specialist Enviroscientists, Inc.

  2. Goal of Study • Western Regional Air Partnership (WRAP) http://wrapair.org • Causes of Haze Assessment (COHA) • Goal: provide assessment of Class I areas through integrated approach • www.coha.dri.edu

  3. Overview • Introduction • Methodology • Analysis • Results & Discussion: Case Studies • Summary

  4. What is Spatial Representativeness? • Area within which pollutant concentrations are approximately constant • Quantitative and qualitative approach to investigate equivalency of measurements

  5. Why is it important? • Data assessments can determine dependence and elicit solutions • Comprehensive picture of a complex system • Tool to assess degree to which measured concentrations can be derived from reference points • Optimal network design

  6. Why is it Important? (cont.) • Evaluation tool to help more efficiently in mediation of environmental problems • Understanding regional visibility & reduction

  7. Introduction • Visibility reduction 1977 CAA • USEPA Regional Haze Rule, Final (40 CFR 51, 1999) • Interagency Monitoring of Protected Visual Environments = IMPROVE (1985) • 5 regional organizations

  8. The IMPROVE Network: Objectives • Federally mandated Class I areas • National parks, monuments, wilderness areas • Identify current conditions of visibility • Determine aerosol species and sources • Document trends • Cultivate representative monitoring network

  9. The IMPROVE Network • 163 sites • 1-in-3 day sampling • 4 cyclone-based modules • Coarse mass & speciated fine aerosols

  10. The Improve Network bext visibility • Light Extinction Formula • bext= 3*f(RH)[Sulfate] + 3*f(RH)[Nitrate] + 4*[Organic Carbon] + 10*[Elemental Carbon] + 1*[ Fine Soil] + 0.6*[Coarse Mass]+ 10 • Concentrations [ ] Units=μg/m3 • Units= Mm-1, proportional to amount of light lost over distance of 1 million meters • Rayleigh Scattering= 10 Mm-1, proportional 0.0 deciviews or 400 km

  11. Research Objectives • Determine spatial representativeness of IMPROVE monitors- WRAP • WA, OR, CA, NV, ID, ND, SD, CO, AZ, NM, TX • 14 Physiographic Regions

  12. Considerations • What are most dominant chemical species during 20% worst visibility days within a region? • What are practical statistical and spatial analysis methods? • How do concentrations vary by season?

  13. Considerations • How can expected average concentrations be determined for a region? • What is a method to test validity?

  14. Methodology • Data • 1997-2002, 54 monitors w/most complete data • Six aerosol species • Sulfates, nitrates, organic carbon (OC), elemental carbon (EC), fine soil, coarse mass (CM) • Focus: Upper 20% of calculated visibility impairment values or 20% worst visibility days

  15. Assumptions • All elemental sulfur is from sulfate -> ammonium sulfate • All nitrate -> ammonium nitrate • Total organic carbon= C released in four steps (OC1-OC4) + pyrolized organics (OP) Thermal Optical Reflectance (TOR) analysis of quartz filter

  16. Assumptions • Elemental carbon (light absorbing carbon) = EC fractions (EC1-EC3) – pyrolized organics (OP) TOR analysis of quartz filter • Fine soil = sum of Al, Si, K, Ca, Ti particle-induced X-ray emission (PIXE) & Fe X-ray fluorescence (XRF) • Coarse mass = total mass - fine mass

  17. Analysis Procedures • 1) Characterize dynamics of regions • Climate & meteorology: wind patterns & back-trajectory analysis (transport) • Graphically displays % of time an air mass spent in an area • Color coded (shading increases w/ residence) • Topography: elevation & intervening terrain • Emission sources and population centers

  18. Analysis Procedures (cont.) • 2) Regional spatial correlation analysis: correlation expected to decrease w/distance • Correlation matrix of aerosol measurements • Distance matrix (km) • Consideration • Correlation of site vs. itself = unity [Artificial]= uncertainty * random #+measurement • [Artificial] plotted at distance of 0

  19. Analysis (cont.) • 3) Criteria correlation cut-off = 0.7 • Rationalize association between monitoring sites • Validation of spatial representativeness • 4) Seasons • Warm months: April to September • Cold months: October to March

  20. Analysis (cont.) • 5) Expected average concentrations • density (like temp.) of atmosphere varies w/ altitude • [Estimated] = [aerosol]* site density density @ sea level • Put conc. into elevation ranges based on natural breaks, then averaged= regional estimated conc. • Uncertainty= standard deviation of average concentrations within elevation range (applicable only with 2 or more sites)

  21. Analysis (cont.) • 6) Test of representativeness • Analyzed sites within each region • Calculated seasonal average concentrations • Uncertainty= average measurement uncertainty • Compared to estimated concentrations

  22. 3.The Northern Great Plains Region • Characteristics • (E) Montana, (NE) Wyoming, & (W) portions of North and South Dakota • Terrain: mostly prairie & rolling hills, mix of forest and grassland • Badlands composed of steep buttes and pinnacles • Sparse population centers • Several coal-fired power plants, west-central ND

  23. The N. Great Plains 6-IMPROVE sites

  24. Residence Time Analysis WICA1 • Warm months • Prevailing winds SE • Bring in dry air from SW U.S. • Moist warm air masses from Gulf of Mexico • Few inversions

  25. Residence Time Analysis MELA1 • Cold months • Cold continental air flowing from N/NW from Canada • L system typical, flushes atmosphere

  26. Aerosol Summary

  27. Aerosol Summary (cont.)

  28. Estimated Concentration (µg/m3)

  29. Test SitesFOPE1 (2yr) NOCH1 (2 yr) FOPE1 30m elev. difference MELA1 [NO3]=0.9 µg/m3

  30. Northern Great Plains Regional Conclusions • Relatively flat terrain with good dispersion of air • Atypical stagnation alleviates regional haze problems during most days • SO4 • representative ~ 180km • Colder months show good agreement out to 700 km

  31. Northern Great Plains Regional Conclusions (cont.) • NO3 • Rep. Distance ~ 450 km, 200km warm months • Factor – chemical nature to volatilize quickly in warmer temperatures or not form at all • OC • Southerly located IMPROVE samplers recorded higher OC concentrations on worst visibility days • Forest fire episodes • Rep. distance (Southern region) ~250 km

  32. Thank you Questions?

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