Historic PM2.5/PM10 concentrations in the southeastern United States -: Potential implications of the revised particulate matter standard

This report summarizes a PM2.5/PM10 particulate matter data set consisting of 861 PM2.5/PM10 sample pairs collected with dichotomous samplers by the Tennessee Valley Authority (TVA) from 1982 to 1991. Eight monitoring stations, ranging from urban-industrial to rural-background, were operated across three east-central U.S. states. Annual average PM2.5 concentrations ranged from 12.6 to 21.3 micrograms per cubic meter (mu g/m(3)), with an overall mean of 15.7 mu g/m(3). Likewise, annual average PM10 concentrations ranged from 17.8 to 33.7 mu g/m(3), with an overall mean of 23.7 mu g/m(3). High summer-low winter seasonality was evident, particularly for PM2.5, with the highest monthly PM2.5 and PM10 concentrations in August (26.4 and 37.5 mu g/m(3), respectively) and the lowest in February (9.9 and 15.3 mu g/m(3), respectively). A strong association (r(2) = 0.84) was found between PM2.5 and PM10 mass with PM2.5 mass contributing, on average, 67% of PM10 mass. Applying TVA's PM2.5/PM10 ratio to recent (1993-1995) regional high-volume PM10 Aerometric Information Retrieval System (AIRS) data for the east-central United States suggests that as many as 80% of monitored counties would have equaled or exceeded the level of the new annual PM2.5 metric of 15 mu g/m(3). A decline in average PM2.5 mass on the order of 3-5 mu g/m(3) from 1982 through 1991 is also suggested. Daily PM2.5 mass appears to be reasonably well associated (r = 0.47) with maximum hourly ozone during the warmer months (spring through fall). Sulfate compounds comprise a major portion of the measured PM2.5 mass, with that fraction being highest in the summer months. Viewed collectively, these data suggest that although compliance with the annual and 24-hr PM10 and 24-hr PM2.5 metrics should prove readily attainable, the annual PM2.5 metric will present a major regulatory management challenge for much of the east-central United States.