1. Spatial Pattern of PM2.5 over the US PM2.5 FRM Network Analysis for the First Year: July 1999-June 2000 Prepared for EPA OAQPS Richard Scheffe by Rudolf B. Husar Center for Air Pollution Impact and Trend Analysis, CAPITA Washington University, St. Louis Draft, March, 2001

2. The PM2.5 FRM Network The evolving PM2.5 network provides that data for evaluation compliance with the NAAQS for PM2.5 The network begun operation in late 1998 using the Federal Reference Method (FRM) Further information on the FRM PM network is on the EPA AMPTIC website.EPA AMPTIC The analysis of the early data (July 2000) is reported by EPA in Initial Summary of Preliminary 1999 Fine Particulate Matter (PM2.5 ) Monitoring Data.Initial Summary of Preliminary 1999 Fine Particulate Matter (PM2.5 ) Monitoring Data This progress report examines the evolution of the network and presents the seasonal and annual PM2.5 maps based on the data in AIRS as of January 2001.

3. PM2.5 FRM Network Evolution The FRM PM2.5 network grow mostly in early 1999. The three colors represent the data content in AIRS as of July 00, Oct 00 and Jan 01. By January 2000 there were ~720 stations monitoring every 6 th day, ~620 stations every 3 rd day and ~100 sites reported daily data

4. PM2.5 FRM Network: Evolution of Spatial Coverage The spatial coverage of the PM2.5 network has increased somewhat: July 99 (672 stations), Oct. 99 (717), Jan. 00 (753), April 00 (751). There are station clusters in the Washington DC-Boston megalopolis, around the Great Lakes, Florida and parts of California and Washington. The station density is low over Alabama, the Texas-N. Dakota the range and the Rocky Mountain states and July 99 Jan 00 Oct 99 Apr 00

5. Annual PM2.5 Concentration Estimates The map is based on AIRS PM2.5 data (as of January 01). The length and spatial coverage of the data are uneven. The annual PM2.5 map spatial show –A remarkably uniform regional distribution over the East (12-18  g/m 3 ). –Urban-metropolitan areas over the East are slightly above (1-2  g/m 3 ) their surrounding region –There are PM2.5 ‘hot spots’ in the valleys of the West (San Joaquin and South Coast Air Basins)

6. PM2.5 Annual Exceedance Regions CRUDE ESTIMATES – inadequate data Potential PM2.5 exceedance regions (>12  g/m 3 ) Entire non-coastal Eastern US (East of Mississippi) San Joaquin and South Coast Air Basins ‘Specks’ of Montana, Texas Possible PM2.5 exceedance regions (>12  g/m 3 ) Entire E. US except New England, Florida, Upper Midwest Parts of the Texas, Arizona, Oregon, Montana Potentially significant exceedance (>12  g/m 3 ) Georgia-E. Tennessee corridor San Joaquin and South Coast Air Basins Parts of the Ohio River Valley

7. PM2.5, PM10 and Estimated PM Coarse Maps Measured Annual PM2.5 Concentration based on the 1999-2000 FRM network data Estimated Annual PMCoarse Concentration PMCoarse = PM10 – PM2.5 Difference of the aggregated PM10 and PM2.5 Note: Sampling methods differ; estimate uncertain. Measured Annual PM10 Concentration based on FRM PM10 data in AIRS.

8. PM2.5 Seasonal Concentration Pattern The entire country shows pronounced seasonality: summer peak in the East, fall/winter peak in the West The highest regional PM2.5 concentration is over the Southeast in the summer season (>21  g/m 3 ). The regional Quarter 1 concentrations are highest around the Great Lakes, Georgia and California Jan, Feb, Mar Jul, Aug, Sep Apr, May, Jun Oct, Nov, Dec Note: The spatial pattern are based on July 1999-June 2000 data. Preliminary analysis shows that the second year of PM2.5 FRM data has a different pattern over the East.

9. PM2.5 Urban/Rural Pattern In the winter months the PM2.5 is highest (16-20  g/m 3 ) is the urban areas of the industrial corridor, Illinois-New York. The remote sites of the East show 8-12  g/m 3 seasonal average concentration. In the summer months, the Eastern PM2.5 is highest (22-26  g/m 3 ) over a broad region of the the Southeast, adjacent to the S. Appalachian Mts. In the summer, urban sites show seasonal average PM2.5 only 1-2  g/m 3 above the surrounding regional values. Hence, urban excess PM2.5 in the East is a winter phenomenon. In the summer, the PM2.5 is regional.

10. Summary of PM2.5 FRM Network Evolution and Pattern By January 2000 there were ~600-700 FRM stations, ~100 sites with daily data The PM2.5 network is significantly clustered near urban-metro areas The annual PM2.5 map shows a remarkably uniform regional distribution over the East and ‘hot spots’ over the West Virtually the entire Eastern US is in the vicinity of the annual NAAQS, (15 +/- 3  g/m 3) PM10 is dominated by PM2.5 in the East and PMCoarse over the Midwest and West. Over the East, the seasonal concentration is highest in the summer, while the ‘dirty’ Western valleys peak in the fall/winter.