| Title: | Synergistic O(3) + OH oxidation pathway to extremely low-volatility dimers revealed in beta-pinene secondary organic aerosol |
| Author(s): | Kenseth CM; Huang Y; Zhao R; Dalleska NF; Hethcox JC; Stoltz BM; Seinfeld JH; |
| Address: | "Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125. Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125; seinfeld@caltech.edu. Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125" |
| ISSN/ISBN: | 1091-6490 (Electronic) 0027-8424 (Print) 0027-8424 (Linking) |
| Abstract: | "Dimeric compounds contribute significantly to the formation and growth of atmospheric secondary organic aerosol (SOA) derived from monoterpene oxidation. However, the mechanisms of dimer production, in particular the relevance of gas- vs. particle-phase chemistry, remain unclear. Here, through a combination of mass spectrometric, chromatographic, and synthetic techniques, we identify a suite of dimeric compounds (C(15-19)H(24-32)O(5-11)) formed from concerted O(3) and OH oxidation of beta-pinene (i.e., accretion of O(3)- and OH-derived products/intermediates). These dimers account for an appreciable fraction (5.9-25.4%) of the beta-pinene SOA mass and are designated as extremely low-volatility organic compounds. Certain dimers, characterized as covalent dimer esters, are conclusively shown to form through heterogeneous chemistry, while evidence of dimer production via gas-phase reactions is also presented. The formation of dimers through synergistic O(3) + OH oxidation represents a potentially significant, heretofore-unidentified source of low-volatility monoterpene SOA. This reactivity also suggests that the current treatment of SOA formation as a sum of products originating from the isolated oxidation of individual precursors fails to accurately reflect the complexity of oxidation pathways at play in the real atmosphere. Accounting for the role of synergistic oxidation in ambient SOA formation could help to resolve the discrepancy between the measured atmospheric burden of SOA and that predicted by regional air quality and global climate models" |
| Keywords: | atmospheric accretion chemistry dimer formation monoterpenes secondary organic aerosol synergistic oxidation; |
| Notes: | "PubMed-not-MEDLINEKenseth, Christopher M Huang, Yuanlong Zhao, Ran Dalleska, Nathan F Hethcox, J Caleb Stoltz, Brian M Seinfeld, John H eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. 2018/08/05 Proc Natl Acad Sci U S A. 2018 Aug 14; 115(33):8301-8306. doi: 10.1073/pnas.1804671115. Epub 2018 Aug 3" |
