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Published September 1, 2015 | Supplemental Material
Journal Article Open

Formation of Low Volatility Organic Compounds and Secondary Organic Aerosol from Isoprene Hydroxyhydroperoxide Low-NO Oxidation


Gas-phase low volatility organic compounds (LVOC), produced from oxidation of isoprene 4-hydroxy-3-hydroperoxide (4,3-ISOPOOH) under low-NO conditions, were observed during the FIXCIT chamber study. Decreases in LVOC directly correspond to appearance and growth in secondary organic aerosol (SOA) of consistent elemental composition, indicating that LVOC condense (at OA below 1 μg m^(–3)). This represents the first simultaneous measurement of condensing low volatility species from isoprene oxidation in both the gas and particle phases. The SOA formation in this study is separate from previously described isoprene epoxydiol (IEPOX) uptake. Assigning all condensing LVOC signals to 4,3-ISOPOOH oxidation in the chamber study implies a wall-loss corrected non-IEPOX SOA mass yield of ∼4%. By contrast to monoterpene oxidation, in which extremely low volatility VOC (ELVOC) constitute the organic aerosol, in the isoprene system LVOC with saturation concentrations from 10^(–2) to 10 μg m^(–3) are the main constituents. These LVOC may be important for the growth of nanoparticles in environments with low OA concentrations. LVOC observed in the chamber were also observed in the atmosphere during SOAS-2013 in the Southeastern United States, with the expected diurnal cycle. This previously uncharacterized aerosol formation pathway could account for ∼5.0 Tg yr^(–1) of SOA production, or 3.3% of global SOA.

Additional Information

© 2015 American Chemical Society. Received: April 23, 2015; Revised: July 17, 2015; Accepted: July 24, 2015; Published: July 24, 2015. This work was supported by grants NSF AGS-1243354, 1243356, 1247421, and 1246918, NOAA NA13OAR4310063, and DOE (BER/ASR) DE-SC0011105. J.K. is grateful for fellowships from CIRES, CU Graduate School, and EPA STAR (FP-91770901-0). We are grateful to the many contributions to the FIXCIT study made by the staff and students of the Wennberg and Seinfeld groups, and fellow participants. We also thank Profs. P. Ziemann and B. Aumount for useful discussions.

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