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      Airborne measurements of organosulfates over the continental U.S.

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          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 (SO 2), which contributes to aerosol acidity.

          Key Points

          • IEPOX sulfate is an isoprene SOA tracer at acidic and low NO conditions

          • Glycolic acid sulfate may be more abundant than IEPOX sulfate globally

          • SO 2 impacts IEPOX sulfate by increasing aerosol acidity and water uptake

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          Most cited references74

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          Climate forcing by anthropogenic aerosols.

          Although long considered to be of marginal importance to global climate change, tropospheric aerosol contributes substantially to radiative forcing, and anthropogenic sulfate aerosol in particular has imposed a major perturbation to this forcing. Both the direct scattering of shortwavelength solar radiation and the modification of the shortwave reflective properties of clouds by sulfate aerosol particles increase planetary albedo, thereby exerting a cooling influence on the planet. Current climate forcing due to anthropogenic sulfate is estimated to be -1 to -2 watts per square meter, globally averaged. This perturbation is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign. Thus, the aerosol forcing has likely offset global greenhouse warming to a substantial degree. However, differences in geographical and seasonal distributions of these forcings preclude any simple compensation. Aerosol effects must be taken into account in evaluating anthropogenic influences on past, current, and projected future climate and in formulating policy regarding controls on emission of greenhouse gases and sulfur dioxide. Resolution of such policy issues requires integrated research on the magnitude and geographical distribution of aerosol climate forcing and on the controlling chemical and physical processes.
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            Ubiquity and dominance of oxygenated species in organic aerosols in anthropogenically-influenced Northern Hemisphere midlatitudes

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              Secondary organic aerosol formation from anthropogenic air pollution: Rapid and higher than expected

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                Author and article information

                Journal
                J Geophys Res Atmos
                J Geophys Res Atmos
                jgrd
                Journal of Geophysical Research. Atmospheres
                John Wiley & Sons, Ltd (Chichester, UK )
                2169-897X
                2169-8996
                16 April 2015
                03 April 2015
                : 120
                : 7
                : 2990-3005
                Affiliations
                [1 ]Chemical Sciences Division, Earth System Research Laboratory, NOAA Boulder, Colorado, USA
                [2 ]Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder Boulder, Colorado, USA
                [3 ]Department of Chemistry, University of Wisconsin-Madison Madison, Wisconsin, USA
                [4 ]Now at Department of Chemistry and Chemical Biology, Harvard University Cambridge, Massachusetts, USA
                [5 ]Division of Geology & Planetary Sciences Pasadena, California, USA
                [6 ]Division of Engineering and Applied Science Pasadena, California, USA
                [7 ]Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens Universität Innsbruck Innsbruck, Austria
                [8 ]Now at Department of Chemistry, University of Olso Oslo, Norway
                [9 ]Department of Chemistry and Biochemistry, University of Colorado Boulder Boulder, Colorado, USA
                [10 ]NASA Langley Research Center Hampton, Virginia, USA
                [11 ]Department of Chemistry, University of California Irvine, California, USA
                Author notes
                Correspondence to: J. Liao,, jin.liao@ 123456noaa.gov
                Article
                10.1002/2014JD022378
                4677836
                26702368
                85d9f6b8-6a4d-4dcd-a2ec-4c8f78134089
                ©2015. The Authors.

                This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

                History
                : 01 August 2014
                : 25 February 2015
                : 26 February 2015
                Categories
                Research Articles

                organosulfate,iepox sulfate,glycolic acid sulfate,free troposphere aerosols,aerosol acidity,relative humidity

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