Historic PM/PM Concentrations in the Southeastern United States-Potential Implications of the Revised Particulate Matter Standard.

This report summarizes a PM/PM particulate matter data set consisting of 861 PM/PM 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 PM concentrations ranged from 12.6 to 21.3 micrograms per cubic meter (μg/m), with an overall mean of 15.7 μg/m. Likewise, annual average PM concentrations ranged from 17.8 to 33.7 μg/m, with an overall mean of 23.7 μg/m. High summer-low winter seasonality was evident, particularly for PM, with the highest monthly PM and PM concentrations in August (26.4 and 37.5 μg/m, respectively) and the lowest in February (9.9 and 15.3 μg/m, respectively). A strong association (r = 0.84) was found between PM and PM mass with PM mass contributing, on average, 67% of PM mass. Applying TVA's PM/PM ratio to recent (1993-1995) regional high-volume PM 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 PM metric of 15 μg/m. A decline in average PM mass on the order of 3-5 μg/m from 1982 through 1991 is also suggested. Daily PM 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 PM mass, with that fraction being highest in the summer months. Viewed collectively, these data suggest that although compliance with the annual and 24-hr PM and 24-hr PM metrics should prove readily attainable, the annual PM metric will present a major regulatory management challenge for much of the east-central United States.