Network Assessment Based on

Daily Max Ozone Concentration

Prepared for EPA OAQPS

Richard Scheffe

by

Rudolf B. Husar and Stefan R. FalkeCenter for Air Pollution Impact and Trend Analysis, CAPITA

Washington University, St. Louis

December 2000

Network Assessment Based on Ozone Concentration

    

AQ Management Activity Geographic Info. Need Station Measure

Risk assessment Pollutant concentration 4th highest O3

Risk Assessment Persons/Station

Compliance evaluation Conc. vicinity to NAAQS Deviation from NAAQS

Reg./local source attribution & tracking Spatial coverage Area of Sampling Zone

All above Estimation uncertainty Meas. & estimate difference

Persons in sampling zone

• There are at least five different measures that represent the information need for (1) risk assessment, (2) compliance monitoring and (3) tracking are listed below.

• The daily max O3 concentration measures the environmental stress on the population. The specific measure used id the 4th highest 8hr daymax ozone averaged over 93-95.

• Using this objective measure, the station with the largest daily max is ranked #1.

The Ozone Database used for Network Assessment

• The ozone datasets were quality controlled and fused from the AIRS (491 stations) and CastNet (32 stations).

• The AIRS sites are clustered mainly in urban-metropolitan areas while the CastNet sites cover rural regions.

• The concentration metric used were the 4th highest daily 8 hr average during 1993-95 and the 90%-tile daily max ozone, 1990-95.

• This integrated ozone data set was used for the OTAG Air Quality Analysis Workgroup.

4th Highest and 90th Percentile Ozone Concentration

• The two ozone concentration metric show very similar spatial pattern.

• The peak values occur in metro areas over the NE Megalopolis, Atlanta, Houston, Dallas, downwind of Chicago and a broad area over the Ohio River Valley.

• At the edges (four ‘corners’) of EUS, the O3 levels are near the troposphereic background.

Ranking by Daily Max Concentration• The daily max concentration is

a factor in health risk.

• The stations with the highest O3 levels (red) are located over the NE Megalopolis, Ohio River Valley and the urban center in the Southeast: Dallas, Houston, Atlanta.

• The stations with the lowest O3 levels (blue) are located throughout the remainder EUS.

• Contiguous regions of low O3 are found in Florida, Upper Midwest, and the inland part of the Northeast.

• From O3 exposure perspective, the blue stations are ranked lowest.