The Southeastern Aerosol Research and Characterization (SEARCH) study: Temporal trends in gas and PM concentrations and composition, 1999–2010

Abstract

Emissions and secondary pollutants show complex relationships that depend on year-to-year variations in dispersion and atmospheric chemistry. The observed response of 03 to NOx and VOC emissions in the Southeast implies that continuing reductions of precursor emissions, probably achieved through vehicle fleet turnover and emission control measures, will be needed to attain the National Ambient Air Quality Standard for O3. Reductions in fine particle concentrations have resulted from reductions of primary PM, especially EC and a portion of OM, and from reduction of gas precursors known to form particles, especially SO4 from SO2. Continued reduction of PM2.5 mass concentrations will require attention to organic constituents, which may be complicated by potentially unmanageable biogenic species present in the Southeast.