Potential of Aerosol Liquid Water to Facilitate Organic Aerosol Formation: Assessing Knowledge Gaps about Precursors and Partitioning.
Isoprene epoxydiol (IEPOX), glyoxal, and methylglyoxal are ubiquitous water-soluble organic gases (WSOGs) that partition to aerosol liquid water (ALW) and clouds to form aqueous secondary organic aerosol (aqSOA). Recent laboratory-derived Setschenow (or salting) coefficients suggest glyoxal's potential to form aqSOA is enhanced by high aerosol salt molality, or "salting-in". In the southeastern U.S., aqSOA is responsible for a significant fraction of ambient organic aerosol, and correlates with sulfate mass. However, the mechanistic explanation for this correlation remains elusive, and an assessment of the importance of different WSOGs to aqSOA is currently missing. We employ EPA's CMAQ model to the continental U.S. during the Southern Oxidant and Aerosol Study (SOAS) to compare the potential of glyoxal, methylglyoxal, and IEPOX to partition to ALW, as the initial step toward aqSOA formation. Among these three studied compounds, IEPOX is a dominant contributor, ∼72% on average in the continental U.S., to potential aqSOA mass due to Henry's Law constants and molecular weights. Glyoxal contributes significantly, and application of the Setschenow coefficient leads to a greater than 3-fold model domain average increase in glyoxal's aqSOA mass potential. Methylglyoxal is predicted to be a minor contributor. Acid or ammonium - catalyzed ring-opening IEPOX chemistry as well as sulfate-driven ALW and the associated molality may explain positive correlations between SOA and sulfate during SOAS and illustrate ways in which anthropogenic sulfate could regulate biogenic aqSOA formation, ways not presently included in atmospheric models but relevant to development of effective control strategies.
Department of Environmental Sciences, Rutgers University , 14 College Farm Road, New Brunswick, New Jersey 08901, United States.
Neha
0000-0003-4658-2977
N
Sareen
Department of Chemistry and Biochemistry, University of Colorado , UCB 215, Boulder, Colorado 80309, United States.|Cooperative Institute for Research in Environmental Sciences, University of Colorado , UCB 216, Boulder, Colorado 80309, United States.
Eleanor M
EM
Waxman
Department of Environmental Sciences and Engineering, Gillings School of Public Health, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
Barbara J
BJ
Turpin
Department of Chemistry and Biochemistry, University of Colorado , UCB 215, Boulder, Colorado 80309, United States.|Cooperative Institute for Research in Environmental Sciences, University of Colorado , UCB 216, Boulder, Colorado 80309, United States.
Rainer
0000-0002-0899-1369
R
Volkamer
Department of Environmental Sciences, Rutgers University , 14 College Farm Road, New Brunswick, New Jersey 08901, United States.
Annmarie G
0000-0002-8574-1507
AG
Carlton
D000336:Aerosols / Q000737:chemistry; D001272:Atmosphere / Q000737:chemistry*; D006037:Glyoxal / Q000737:chemistry; D013431:Sulfates / Q000737:chemistry; D014867:Water
D000336:Aerosols; D013431:Sulfates; D014867:Water; D006037:Glyoxal