1. Natural and Anthropogenically Influenced Isoprene Oxidation in Southeastern United States and Central Amazon.
- Author
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Yee LD, Isaacman-VanWertz G, Wernis RA, Kreisberg NM, Glasius M, Riva M, Surratt JD, de Sá SS, Martin ST, Alexander ML, Palm BB, Hu W, Campuzano-Jost P, Day DA, Jimenez JL, Liu Y, Misztal PK, Artaxo P, Viegas J, Manzi A, de Souza RAF, Edgerton ES, Baumann K, and Goldstein AH
- Subjects
- Aerosols analysis, Brazil, Butadienes, Pentanes, Southeastern United States, Air Pollutants, Hemiterpenes
- Abstract
Anthropogenic emissions alter secondary organic aerosol (SOA) formation chemistry from naturally emitted isoprene. We use correlations of tracers and tracer ratios to provide new perspectives on sulfate, NO
x , and particle acidity influencing isoprene-derived SOA in two isoprene-rich forested environments representing clean to polluted conditions-wet and dry seasons in central Amazonia and Southeastern U.S. summer. We used a semivolatile thermal desorption aerosol gas chromatograph (SV-TAG) and filter samplers to measure SOA tracers indicative of isoprene/HO2 (2-methyltetrols, C5 -alkene triols, 2-methyltetrol organosulfates) and isoprene/NOx (2-methylglyceric acid, 2-methylglyceric acid organosulfate) pathways. Summed concentrations of these tracers correlated with particulate sulfate spanning three orders of magnitude, suggesting that 1 μg m-3 reduction in sulfate corresponds with at least ∼0.5 μg m-3 reduction in isoprene-derived SOA. We also find that isoprene/NOx pathway SOA mass primarily comprises organosulfates, ∼97% in the Amazon and ∼55% in Southeastern United States. We infer under natural conditions in high isoprene emission regions that preindustrial aerosol sulfate was almost exclusively isoprene-derived organosulfates, which are traditionally thought of as representative of an anthropogenic influence. We further report the first field observations showing that particle acidity correlates positively with 2-methylglyceric acid partitioning to the gas phase and negatively with the ratio of 2-methyltetrols to C5 -alkene triols.- Published
- 2020
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