Airborne measurements of organosulfates over the continental U.S.

Abstract

Organosulfates are important secondary organic aerosol (SOA) components and good tracers for aerosol heterogeneous reactions. However, the knowledge of their spatial distribution, formation conditions, and environmental impact is limited. In this study, we report two organosulfates, an isoprene-derived isoprene epoxydiols (IEPOX) (2,3-epoxy-2-methyl-1,4-butanediol) sulfate and a glycolic acid (GA) sulfate, measured using the NOAA Particle Analysis Laser Mass Spectrometer (PALMS) on board the NASA DC8 aircraft over the continental U.S. during the Deep Convective Clouds and Chemistry Experiment (DC3) and the Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS). During these campaigns, IEPOX sulfate was estimated to account for 1.4% of submicron aerosol mass (or 2.2% of organic aerosol mass) on average near the ground in the southeast U.S., with lower concentrations in the western U.S. (0.2–0.4%) and at high altitudes (<0.2%). Compared to IEPOX sulfate, GA sulfate was more uniformly distributed, accounting for about 0.5% aerosol mass on average, and may be more abundant globally. A number of other organosulfates were detected; none were as abundant as these two. Ambient measurements confirmed that IEPOX sulfate is formed from isoprene oxidation and is a tracer for isoprene SOA formation. The organic precursors of GA sulfate may include glycolic acid and likely have both biogenic and anthropogenic sources. Higher aerosol acidity as measured by PALMS and relative humidity tend to promote IEPOX sulfate formation, and aerosol acidity largely drives in situ GA sulfate formation at high altitudes. This study suggests that the formation of aerosol organosulfates depends not only on the appropriate organic precursors but also on emissions of anthropogenic sulfur dioxide (SO2), which contributes to aerosol acidity.Key PointsIEPOX sulfate is an isoprene SOA tracer at acidic and low NO conditions Glycolic acid sulfate may be more abundant than IEPOX sulfate globally SO2 impacts IEPOX sulfate by increasing aerosol acidity and water uptake

Secondary organic aerosol formation from ambient air in an oxidation flow reactor in central Amazonia

“…IEPOX-SOA, while representing a type of SOA, was also not expected to be produced in the OFR. In the atmosphere, IEPOX-SOA is formed via reactive uptake of gas-phase IEPOX onto acidic aerosols Froyd et al, 2010;Surratt et al, 2010;Lin et al, 2012;Liao et al, 2015). As detailed in Hu et al (2016), IEPOX can be formed in the gas phase in the OFR at accelerated rates, but the rate of reactive uptake in the OFR does not increase with the increased OH concentrations, resulting in negligible formation of IEPOX-SOA in the OFR.…”

Simulating the SOA formation of isoprene from partitioning and aerosol phase reactions in the presence of inorganics

“…7. IEPOX has been demonstrated to be an important precursor to ambient (Budisulistiorini et al, 2015; and laboratory-generated (Lin et al, 2012;Paulot et al, 2009) isoprene SOA leading to the formation of 2-methyltetrols , OS (Liao et al, 2015), and other species through aerosol phase reactions in which IEPOX products contribute up to 33 % of ambient OM in the southeast US . The formation of IEPOXderived SOA has been shown to be primarily from the reactive uptake in the presence of LWC and [H + ] but is most highly correlated with aerosol acidity (Gaston et al, 2014).…”

Organosulfates in atmospheric aerosol: synthesis and quantitative analysis of PM&lt;sub&gt;2.5&lt;/sub&gt; from Xi'an, northwestern China

“…A very recent study revealed a previously unrecognized pathway for organosulfate formation through the heterogeneous reaction of SO 2 with the unsaturated bond in oleic acid (Shang et al, 2016). A number of biogenic organosulfates have been observed in ambient aerosol, in particular, isoprene-derived organosulfates (e.g., Kristensen et al, 2011;He et al, 2014;Liao et al, 2015;Budisulistiorini et al, 2015). A recent study reported the formation of aromatic organosulfates by photochemical oxidation of polycyclic aromatic hydrocarbons (PAHs) in the presence of sulfate seed particles (Riva et al, 2016).…”

“…To date, many studies of organosulfates have remained at the qualitative level, although a limited number of studies have provided quantitative or semi-quantitative analysis of certain organosulfates (e.g., Kundu et al, 2013;Staudt et al, 2014;Ma et al, 2014;Olson et al, 2011;Hettiyadura et al, 2017). Moreover, several studies show that organosulfates are present as a wide range of species with individual species such as the organosulfate derived from isoprene epoxydiols (IEPOXs) contributing 0.2-1.4 % of the total organic aerosol mass (Liao et al, 2015). This further complicates the quantification of organosulfates.…”