| PM2.5 mass and composition were measured at three locations in Atlanta, GA for one year, beginning in March 1999. Particulate mass was measured continuously (resolvable down to one-minute intervals) using three tapered element oscillating microbalance (TEOM) instruments from Rupprecht and Patashnick. The monitors were located at Jefferson Street (the 1999 EPA "Supersite"), which is approximately 1.5 miles NW of downtown Atlanta; Fort McPherson Army Base, approximately 7 miles SW of downtown; and Tucker, GA, approximately 12 miles NE of downtown. For the year, maximum 1-hour PM2.5 concentrations were 87.9 mug/m3, 86.2 mug/m 3, and 73.3 mug/m3, at Tucker, Fort McPherson and Jefferson Street, respectively; maximum 24-hour concentrations were 51.5 mug/m 3, 44.3 mug/m3 and 46.3 mug/m3, and annual averages were 21.2 mug/m3, 19.3 mug/m 3, 21.0 mug/m3 respectively.; In addition to the PM2.5 continuous mass measurements, particle composition monitors (PCMs) based on the Atmospheric Research and Analysis (ARA) design were constructed and sited in order to gain integrated, 24-hour composition data and compare to the continuous mass instruments. The multi-channel PCMs were located at Fort McPherson, Tucker, and South Dekalb College, which is approximately 9 miles SE of downtown Atlanta. The species collected on various filter media included ions (ammonium, sulfate, and nitrate), elemental and organic carbon, and metals (Mg through Pb). For the three sites, including PM2.5 mass measurements taken at South Dekalb by the Georgia Department of Natural Resources, approximately 31% of the mass was identified as organic carbon, 22% as sulfate, 9% as ammonium, 6.4% as nitrate, 2% as elemental carbon, 3.2% as metals (crustal elements), and the remaining 26.4% was unidentifiable. Application of multiplicative factors to account for related species not determined by the laboratory analyses yielded a more closed material balance (<10% unidentifiable).; In one set of analyses, the integrated and continuous data were examined for seasonal and day-of-week temporal trends. The results indicated increasing ambient PM2.5 concentrations for mass and most ionic and carbonaceous species during the summer months. Nitrate, which showed a wintertime peak, was the exception. These observations suggest the importance of photochemistry in the Atlanta aerosol.; In another set of analyses, the data were examined for spatial trends using a geographic information system (GIS) model. Hourly and daily data from the monitoring sites were spatially resolved using the universal Kriging method in ARC/InfoRTM to estimate a smooth surface from irregularly spaced data points. The results indicated a reasonably homogeneous PM 2.5 concentration field, with infrequent significant spatial differences resulting from local meteorology and large point sources.; Finally, the particulate data were combined with routinely collected gas-phase and meteorological data and modeled, in an effort to determine the statistical relationships between PM2.5 and other pollutants. The models developed accounted for over 70% of the temporal variance in the aerosol measurements. The development of spatial models proved unproductive due to data limitations. |
