Results of Ambient Air Analyses in Support of Transport Rule

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Results of Ambient Air Analysesin Support of
Transport Rule

• Presentation for RPO Workshop
• November 2003

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Results to be Covered

• What are the main constituents of PM2.5?
• Are these regionally or locally generated?
• What are the largest emission source types and
  where are they located?
• How consistent are the results based on ambient
  air analyses with those from modeling?

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What are the main constituents of PM2.5 in Urban
Areas?
(1) Sulfate and Total Carbon dominate the eastern
pies (2) Total Carbon dominant in the western
pies, nitrate large fraction in southern CA and
SLC.
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What are the main constituents of PM2.5 in Rural
Areas?
(1) Sulfate and Total Carbon dominate the eastern
pies. (2) West dominated by Total Carbon, crustal
important in southwest and eastern WA.
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Comparison of Urban and Rural Composition
Urban
Rural
Comparison of annual average (March 2001 - Feb
2002) PM2.5 mass and species concentrations.
Urban data from EPAs speciation network and
rural data from IMPROVE network.
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Regional vs. Urban Pollutants
Comparison of annual average (March 2001 - Feb
2002) PM2.5 mass and species concentrations at
paired urban and rural locations. Urban data
from EPAs speciation network and rural data from
IMPROVE network. Average urban concentration is
sum of estimated urban and regional contributions.
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Regional vs. Urban Pollutants
Regional pollutants are typically observed at
similar concentration levels across broad
geographic areas. Urban pollutants are typically
highest in and near urban areas.
Sulfate is mostly a regional problem...the urban
excess is small. Total Carbon appears to be both
a regional and an urban problem, due to various
sources of carbon. Total carbon has three
components Black Carbon (BC) directly
emitted, likely mostly urban Primary Organic
Aerosols (POA) directly emitted, likely mostly
urban Secondary Organic Aerosols (SOA) from
anthropogenic sources and from biogenic sources
(coniferous trees) likely both urban and
regional problem. Nitrate may be both an urban
and a regional problemnote that urban excess
tends to be higher in the North compared to the
South due to climate. Ammonium associates with
Sulfate and Nitrate. Can be a regional and urban
problem depending on the source of
ammonia. Crustal material (not shown) may be
both an urban and a regional problem very small
amounts (lt1 µg/m3) appear in both urban and rural
areas, but may be generated from different
sources.
Comparison of annual average (March 2001 - Feb
2002) PM2.5 mass and species concentrations at
paired urban and rural locations. Urban data
from EPAs speciation network and rural data from
IMPROVE network. Average urban concentration is
sum of estimated urban and regional contributions.
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Regional vs. Urban Pollutants
Sulfate is mostly a regional problem...the urban
excess is small. Total Carbon appears to be both
a regional and an urban problem, due to various
sources of carbon. Total carbon has three
components Black Carbon (BC) directly
emitted, likely mostly urban Primary Organic
Aerosols (POA) directly emitted, likely mostly
urban Secondary Organic Aerosols (SOA) from
anthropogenic sources and from biogenic sources
(coniferous trees) likely both urban and
regional problem. Nitrate may be both an urban
and a regional problemnote that urban excess
tends to be higher in the North compared to the
South due to climate. Ammonium associates with
Sulfate and Nitrate. Can be a regional and urban
problem depending on the source of
ammonia. Crustal material (not shown) may be
both an urban and a regional problem very small
amounts (lt1 µg/m3) appear in both urban and rural
areas, but may be generated from different
sources.
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What are the largest emission source
types?(Based on Source Apportionment Analyses)
(1) Sulfate source type is largest at all sites.
Mobile and nitrate source types are second and
third largest at all sites. (2) Based on
EPA-sponsored SA study in 8 urban
areas. (3) EPA-sponsored 8-cities work consistent
with results from recent compilation of gt 17
published SA works.
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Regions for Largest Emission Source Type (1)
Features Unique to Each City, (2) But They
Intersect
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Where is the Largest Emission Source Type
Located? (Based on Multiple Cities)
Sulfate Source Regions Common to Multiple Sites
1999 SO2 Emissions (Tons/Year)
3
5
Milwaukee
Bronx
Indianapolis
DC
St. Louis
Charlotte

Birmingham
Houston
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Locations of SO2 emissions are consistent with
high-probability regions for Sulfate source
type.
Sulfate Source Regions Common to Multiple Sites
1999 SO2 Emissions (Tons/Year)
3
5
Milwaukee
Bronx
Indianapolis
DC
St. Louis
Charlotte

Birmingham
Houston
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EPA 8-Cities Source Apportionment Study Source
Types and How Much They Contribute
Average Mass Contributions for Main Profiles
(ug/m3)
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Preliminary Consistency Check with Modeling
Results

• Comparison of Bronx Source Region for Sulfate and
  Zero Out Runs
• States with largest impact on Bronx all in High
  Probability Source Region.
• States with small impact on Bronx not in High
  Probability Source Region

ug/m3 sulfate
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Source Apportionment Compilation

• Review of Nearly 20 Recently Published Articles
  Using Source Apportionment Modeling
• Over 35 Eastern Locations
• Common Themes
• Secondary Sulfate/Coal Combustion One of the
  Largest Sources in Almost All Studies
• Secondary Sulfate/Coal Combustion Over 50 of the
  Mass During Some Seasons (mostly summer) in Many
  Studies
• Secondary Organic Mass/Motor Vehicles Identified
  in Most Studies
• Nitrate Dominated Source Identified in About Half
  of the Studies (In studies where back
  trajectories were used, origin of source often
  pointed to areas associated with high ammonia
  emissions)

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Locations Included in Compilation
PLUS Seattle SLC Valley Phoenix
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Recap

• Major species in east are sulfate, OC, and
  nitrate in the west, OC and nitrate.
• Urban/rural comparison indicates that attainment
  in the East is not achievable just with local
  control measures.
• Main sources are combustion from utilities and
  mobile.
• Preliminary assessment shows consistent result
  from observed and predictive analyses.

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Tabular Listing of Locations