Particle partitioning potential of organic compounds is highest in the Eastern US and driven by anthropogenic water A. G. Carlton and B. J. Turpin Dept. of Environmental Sciences, Rutgers University, New Brunswick, NJ 08901, USA
Abstract. Gas-phase water-soluble organic matter (WSOMg) is ubiquitous in
the troposphere. In the summertime, the potential for these gases to
partition to particle-phase liquid water (H2Optcl) where they
can form secondary organic aerosol (SOAAQ) is high in the Eastern
US and low elsewhere, with the exception of an area near Los Angeles, CA.
This spatial pattern is driven by mass concentrations of
H2Optcl, not WSOMg. H2Optcl mass
concentrations are predicted to be high in the Eastern US, largely due to
sulfate. The ability of sulfate to increase H2Optcl is
well established and routinely included in atmospheric models; however
WSOMg partitioning to this water and subsequent SOA formation is
not. The high mass concentrations of H2Optcl in the southeast
(SE) US but not the Amazon may help explain why biogenic SOA mass
concentrations are high in the SE US but low in the Amazon. Furthermore,
during the summertime in the Eastern US, the potential for organic gases to
partition into liquid water is greater than their potential to partition into
organic matter (OM) because concentrations of WSOMg and
H2Optcl are higher than semi-volatile gases and OM. Thus,
unless condensed phase yields are substantially different
(> ~ order of magnitude), we expect that SOA formed through
aqueous-phase pathways (SOAAQ) will dominate in the Eastern US.
These findings also suggest that H2Optcl is largely
anthropogenic and provide a previously unrecognized mechanism by which
anthropogenic pollutants impact the amount of SOA mass formed from biogenic
organic emissions. The previously reported estimate of the controllable
fraction of biogenic SOA in the Eastern US (50%) is likely too low.
Citation: Carlton, A. G. and Turpin, B. J.: Particle partitioning potential of organic compounds is highest in the Eastern US and driven by anthropogenic water, Atmos. Chem. Phys., 13, 10203-10214, doi:10.5194/acp-13-10203-2013, 2013.