update on pm 2.5 – the scope of the problem and overview of sources
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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 (~TRANSCRIPT
Update on PM2.5 – The Scope of the Problem and
Overview of Sources
Matthew M. Russell, PhD ENVIRON International Corporation
Los Angeles, CaliforniaApril 15, 2008
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
Particulate Matter: What is it?
PM10
Combustion Particulate Matter
Gasoline exhaust particleDiesel exhaust particle
Source: D. Kittleson, SCAQMD Ultrafine Particle Conference
PM2.5 Sources
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
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)
PM National Ambient Air Quality Standards
PM2.5 Non-Attainment Areas
Primary sources of PM
Secondary sources of PM
EPA: PM2.5 Diesel (US)
Federal Programs Will Reduce PM2.5
But many areas will need additional controls
Example: South Coast Air Basin PM2.5
0
5
10
15
20
25
30
35
40
Nitric Acid Ammonia Nitrate-10 Ammonium-10
Anaheim Los Angeles Diamond Bar Fontana Rubidoux
20052001
Source: SCAQMD
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
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
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