A long-term, dispersion normalized PMF source apportionment of PM2.5 in Atlanta from 2005 to 2019

Abstract

This study assessed the effects of policy implementations and economic drivers on the identified sources of particulate pollution and their contributions to the ambient PM2.5 concentrations in Atlanta, Georgia during 2005–2019. Dispersion-normalized positive matrix factorization (DN-PMF) was applied to account for meteorological impacts on the ambient concentrations. Secondary sulfate, gasoline vehicle, diesel vehicle, biomass burning, secondary nitrate, dust/road dust, aged sea salt, copper and pyrolyzed carbon were resolved for the study period. Among them, secondary sulfate was the largest contributor to the PM2.5 mass concentrations. A substantial decrease in its concentrations was observed both after 2008 and after 2017 due to the implementation of the Georgia Multipollutant Control for Electric Utility Steam Generating Units rule in 2007 and the new Tier 3 Motor Vehicle Emission Standards in 2017. Emissions from gasoline and diesel vehicles as well as secondary nitrate also decreased after 2008. However, the reductions in gasoline and diesel emissions can be attributed to the two years of economic recession, implementation of the Georgia Gasoline Marketing Rule and regulations under the Heavy-Duty Diesel Rule. The decrease in emissions of secondary nitrate was observed after introduction of entire year control on NOx emissions promulgated by the regulations under the Clean Air Interstate rule and the Georgia NOx Emission from Electric Utility Stream Generating Units rule. Alternatively, elevated summer values were characteristic of the biomass burning, pyrolyzed carbon and dust/road dust factors. The elevated summer biomass burning emissions in 2019 were likely due to two wildfires southwest of Atlanta, while the elevated summer dust/road dust factor values were due to transported Saharan dust episodes. Identification of the copper factor at this Atlanta site was linked to the poor venting of a high-volume sampler with a copper brush motor.