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Update on PM 2.5 – The Scope of the Problem and Overview of Sources

Update on PM 2.5 – The Scope of the Problem and Overview of Sources. Matthew M. Russell, PhD ENVIRON International Corporation Los Angeles, California April 15, 2008. Definitions. TSP: Total Suspended Particulate (~<30 microns)

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Update on PM 2.5 – The Scope of the Problem and Overview of Sources

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  1. Update on PM2.5 – The Scope of the Problem and Overview of Sources Matthew M. Russell, PhD ENVIRON International Corporation Los Angeles, California April 15, 2008

  2. Definitions • TSP: Total Suspended Particulate (~<30 microns) • PM10: Coarse and Fine Particles: particles less than 10 microns in “diameter” • PM2.5 (Fine Particles): particles less than 2.5 microns in “diameter” • Ultrafine Particles (UFP): generally particles less than 0.1 microns in “diameter” • Nanoparticles: particles less than 50 nm (nanometers) in “diameter” • 1000 nm in a micron

  3. Particulate Matter: What is it?

  4. PM10

  5. Combustion Particulate Matter Gasoline exhaust particle Diesel exhaust particle Source: D. Kittleson, SCAQMD Ultrafine Particle Conference

  6. PM2.5 Sources

  7. Secondary PM2.5 Aerosol Formation • Ammonia is the source of the predominant base compound in the atmosphere (ammonium – NH4+) • Acids are formed by reaction of combustion by-products • NO2 + OH → HNO3 • SO2 + 2OH → H2SO4 • Under the right conditions, ammonia will join with gaseous acids (e.g. sulfuric and hydrochloric acids) • 2NH3(g) + H2SO4→ 2(NH4)SO4 (aerosol) • NH3(g) + HNO3(g) ↔ NH4NO3(PM) (solid and aerosol) • Ammonium sulfate, then ammonium nitrate

  8. Ammonia: The Step-Child of PM Precursors • A necessary, but not sufficient precursor • Wetter conditions with limited mixing conducive to ammonium aerosol production • Sulfuric acid will preferentially react with any available ammonia first • Ammonium nitrate will be formed ifadditional ammoniaavailable and conditions are conducive • Limiting reactant? • New control programs? Source: After Pandis (2003)

  9. PM National Ambient Air Quality Standards

  10. PM2.5 Non-Attainment Areas

  11. Primary sources of PM

  12. Secondary sources of PM

  13. EPA: PM2.5 Diesel (US)

  14. Federal Programs Will Reduce PM2.5 • But many areas will need additional controls

  15. Example: South Coast Air Basin PM2.5 2001 2005

  16. Source: SCAQMD

  17. What’s Next? Ultrafine Particles (UFP) • Increasing scientific and technical study of UFP • Health effects (number count and composition more important than mass) • Sources and emissions • Ambient concentrations • Potential control programs • South Coast AQMD UFP Conference (April 2006) • Scientific and technical studies presented • Increasing regulatory interest at all levels

  18. UFP and PM2.5 • Potential control program interactions • Some, but not all, DPM filters may also be effective at reducing UFP • New UFP formation may be inversely proportional to PM2.5 (!) • Research at USC suggests : Source: Sioutas, C. SCAQMD Ultrafine Particle Conference

  19. Conclusions • PM2.5 is comprised of many substances • Combustion sources are the major sources of: • primary PM2.5 (e.g., carbon soot, organic aerosols) • secondary precursors (NOx, SOx) • control programs for ozone can reduce PM2.5 • Aggressive controls of combustion sources will be necessary to attain federal standards for worst areas • Ammonia as a precursor needs to be better understood, particularly for ammonia-limited areas • Ultrafine particles (UFP) and future related control programs may directly affect PM2.5 control programs

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