Observational Insights into Aerosol Formation from Isoprene

D.R. Worton, J.D. Surratt, B.W. Lafranchi, A.W.H. Chan, Yunliang Zhao, Robin J. Weber, J.-H. Park, J.B. Gilman, J. De Gouw, C. Park, G. Schade, M. Beaver, J.M.S. Clair, J. Crounse, P. Wennberg, G.M. Wolfe, S. Harrold, J.A. Thornton, D.K. Farmer, K.S. DochertyM.J. Cubison, J.-L. Jimenez, A.A. Frossard, L.M. Russell, Kasper Kristensen, M. Glasius, J. Mao, X. Ren, W. Brune, E.C. Browne, S.E. Pusede, R.C. Cohen, J.H. Seinfeld, A.H. Goldstein

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Abstract

Atmospheric photooxidation of isoprene is an important source of secondary organic aerosol (SOA) and there is increasing evidence that anthropogenic oxidant emissions can enhance this SOA formation. In this work, we use ambient observations of organosulfates formed from isoprene epoxydiols (IEPOX) and methacrylic acid epoxide (MAE) and a broad suite of chemical measurements to investigate the relative importance of nitrogen oxide (NO/NO) and hydroperoxyl (HO) SOA formation pathways from isoprene at a forested site in California. In contrast to IEPOX, the calculated production rate of MAE was observed to be independent of temperature. This is the result of the very fast thermolysis of MPAN at high temperatures that affects the distribution of the MPAN reservoir (MPAN / MPA radical) reducing the fraction that can react with OH to form MAE and subsequently SOA (F). The strong temperature dependence of F helps to explain our observations of similar concentrations of IEPOX-derived organosulfates (IEPOX-OS; ∼1 ng m) and MAE-derived organosulfates (MAE-OS; ∼1 ng m) under cooler conditions (lower isoprene concentrations) and much higher IEPOX-OS (∼20 ng m) relative to MAE-OS (
Original languageEnglish
JournalEnvironmental Science & Technology (Washington)
Volume47
Issue20
Pages (from-to)11403-11413
Number of pages11
ISSN0013-936X
DOIs
Publication statusPublished - 2013

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