Document Type

Article

Publication Date

9-2016

Publication Title

Atmospheric Chemistry and Physics

ISSN

1680-7324

Volume

16

Issue

18

DOI

http://dx.doi.org/10.5194/acp-16-11563-2016

Abstract

Isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA) can contribute substantially to organic aerosol (OA) concentrations in forested areas under low NO conditions, hence significantly influencing the regional and global OA budgets, accounting, for example, for 16-36% of the submicron OA in the southeastern United States (SE US) summer. Particle evaporation measurements from a thermodenuder show that the volatility of ambient IEPOX-SOA is lower than that of bulk OA and also much lower than that of known monomer IEPOX-SOA tracer species, indicating that IEPOX-SOA likely exists mostly as oligomers in the aerosol phase. The OH aging process of ambient IEPOX-SOA was investigated with an oxidation flow reactor (OFR). New IEPOX-SOA formation in the reactor was negligible, as the OFR does not accelerate processes such as aerosol uptake and reactions that do not scale with OH. Simulation results indicate that adding ∼ 100µgm-3 of pure H2SO4 to the ambient air allows IEPOX-SOA to be efficiently formed in the reactor. The heterogeneous reaction rate coefficient of ambient IEPOX-SOA with OH radical (kOH) was estimated as 4.0±2.0 × 10-13cm3molec-1s-1, which is equivalent to more than a 2-week lifetime. A similar kOH was found for measurements of OH oxidation of ambient Amazon forest air in an OFR. At higher OH exposures in the reactor (> 1 × 1012moleccm-3s), the mass loss of IEPOX-SOA due to heterogeneous reaction was mainly due to revolatilization of fragmented reaction products. We report, for the first time, OH reactive uptake coefficients (γOH = 0.59±0.33 in SE US and γOH = 0.68±0.38 in Amazon) for SOA under ambient conditions. A relative humidity dependence of kOH and γOH was observed, consistent with surface-area-limited OH uptake. No decrease of kOH was observed as OH concentrations increased. These observations of physicochemical properties of IEPOX-SOA can help to constrain OA impact on air quality and climate.

Comments

AUTHORS

W. Hu (Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA) W. Hu (Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA) B. B. Palm (Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA) B. B. Palm (Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA) D. A. Day (Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA) D. A. Day (Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA) P. Campuzano-Jost (Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA) P. Campuzano-Jost (Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA) J. E. Krechmer (Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA) J. E. Krechmer (Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA) Z. Peng (Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA) Z. Peng (Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA) S. S. de Sá (John A. Paulson School of Engineering and Applied Sciences Harvard University, Cambridge, MA 01742, USA) S. T. Martin (John A. Paulson School of Engineering and Applied Sciences Harvard University, Cambridge, MA 01742, USA) S. T. Martin (Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 01742, USA) M. L. Alexander (Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, USA) K. Baumann (Atmospheric Research and Analysis Inc., Morrisville, NC 27560, USA) L. Hacker (Institute for Energy and Climate Research – Troposphere (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany) A. Kiendler-Scharr (Institute for Energy and Climate Research – Troposphere (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany) A. R. Koss (Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA) A. R. Koss (Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA) A. R. Koss (Earth System Research Laboratory, NOAA, Boulder, CO 80305, USA) J. A. de Gouw (Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA) J. A. de Gouw (Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA) J. A. de Gouw (Earth System Research Laboratory, NOAA, Boulder, CO 80305, USA) A. H. Goldstein (Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720, USA) A. H. Goldstein (Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720, USA) R. Seco (Department of Earth System Science, University of California, Irvine, CA 92697, USA) S. J. Sjostedt (Earth System Research Laboratory, NOAA, Boulder, CO 80305, USA) J.-H. Park (National Institute of Environmental Research, Incheon 22689, Republic of Korea) A. B. Guenther (Department of Earth System Science, University of California, Irvine, CA 92697, USA) S. Kim (Department of Earth System Science, University of California, Irvine, CA 92697, USA) F. Canonaco (Laboratory of Atmospheric Chemistry, Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland) A. S. H. Prévôt (Laboratory of Atmospheric Chemistry, Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland) W. H. Brune (Department of Meteorology, Pennsylvania State University, University Park, PA 16802, USA) J. L. Jimenez (Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA) J. L. Jimenez (Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA)

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