Sources and their contributions of ambient PM2.5 concentrations in an industrial area of Atlanta from 1998 to 2016

The SouthEastern Aerosol Research CHaracterization (SEARCH) program examined air quality at 6 sites across the southeastern United States. The Jefferson Street site in Atlanta operated from 1998 to 2016 with the collection and chemical characterization of PM_2.5 that provide data suitable for source identification and apportionment with a sufficiently long time series to permit effective trend analyses. Although there have been analyses of parts of these data, there is no prior comprehensive analysis relating the changes in source-specific PM_2.5 with policy implementations and economic drivers. The major sources were secondary sulfate, traffic sources (spark- and compression-ignition vehicles), and secondary nitrate. Several local industrial sources were identified primarily assigned as metal working, but likely including a nearby bus maintenance garage. A combined biomass burning and pyrolyzed organic carbon factor was resolved that reflected the extensive prescribed burning that occurred in the southeastern United States to control larger wildfires and that increased in recent years. The major trends were reductions in concentrations of sulfate and nitrate likely as a result of policies to reduce emissions from coal-fired power plants and mobile sources. Gasoline vehicle contributions uniformly declined, but there was a period of increase diesel concentrations in the middle of the study period for which the cause is unknown.