1. Constraining nucleation, condensation, and chemistry in oxidation flow reactors using size-distribution measurements and aerosol microphysical modeling
- Author
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Massachusetts Institute of Technology. Department of Civil and Environmental Engineering, Massachusetts Institute of Technology. Department of Materials Science and Engineering, Massachusetts Institute of Technology. Department of Mechanical Engineering, Cross, Eben, Hunter, James Freeman, Kroll, Jesse, Jimenez, Jose L., Hodshire, Anna L., Palm, Brett B., Alexander, M. Lizabeth, Bian, Qijing, Campuzano-Jost, Pedro, Day, Douglas A., de Sá, Suzane S., Guenther, Alex B., Hansel, Armin, Jud, Werner, Karl, Thomas, Kim, Saewung, Park, Jeong-Hoo, Peng, Zhe, Seco, Roger, Smith, James N., Pierce, Jeffrey R., Massachusetts Institute of Technology. Department of Civil and Environmental Engineering, Massachusetts Institute of Technology. Department of Materials Science and Engineering, Massachusetts Institute of Technology. Department of Mechanical Engineering, Cross, Eben, Hunter, James Freeman, Kroll, Jesse, Jimenez, Jose L., Hodshire, Anna L., Palm, Brett B., Alexander, M. Lizabeth, Bian, Qijing, Campuzano-Jost, Pedro, Day, Douglas A., de Sá, Suzane S., Guenther, Alex B., Hansel, Armin, Jud, Werner, Karl, Thomas, Kim, Saewung, Park, Jeong-Hoo, Peng, Zhe, Seco, Roger, Smith, James N., and Pierce, Jeffrey R.
- Abstract
Oxidation flow reactors (OFRs) allow the concentration of a given atmospheric oxidant to be increased beyond ambient levels in order to study secondary organic aerosol (SOA) formation and aging over varying periods of equivalent aging by that oxidant. Previous studies have used these reactors to determine the bulk OA mass and chemical evolution. To our knowledge, no OFR study has focused on the interpretation of the evolving aerosol size distributions. In this study, we use size-distribution measurements of the OFR and an aerosol microphysics model to learn about size-dependent processes in the OFR. Specifically, we use OFR exposures between 0.09 and 0.9 equivalent days of OH aging from the 2011 BEACHON-RoMBAS and GoAmazon2014/5 field campaigns. We use simulations in the TOMAS (TwO-Moment Aerosol Sectional) microphysics box model to constrain the following parameters in the OFR: (1) the rate constant of gas-phase functionalization reactions of organic compounds with OH, (2) the rate constant of gas-phase fragmentation reactions of organic compounds with OH, (3) the reactive uptake coefficient for heterogeneous fragmentation reactions with OH, (4) the nucleation rate constants for three different nucleation schemes, and (5) an effective accommodation coefficient that accounts for possible particle diffusion limitations of particles larger than 60nm in diameter. We find the best model-to-measurement agreement when the accommodation coefficient of the larger particles (Dp>60nm) was 0.1 or lower (with an accommodation coefficient of 1 for smaller particles), which suggests a diffusion limitation in the larger particles. When using these low accommodation-coefficient values, the model agrees with measurements when using a published H2SO4-organics nucleation mechanism and previously published values of rate constants for gas-phase oxidation reactions. Further, gas-phase fragmentation was found to have a significant impact upon the size distribution, and including fragm, United States. Department of Energy. Office of Biological and Environmental Research (grant no. DE-SC0011780), United States. National Oceanic and Atmospheric Administration. Office of Atmospheric Chemistry, Carbon Cycle, and Climate Program (cooperative agreement award no. NA17OAR430001), United States. National Oceanic and Atmospheric Administration. Office of Atmospheric Chemistry, Carbon Cycle, and Climate Program (cooperative agreement award no. NA17OAR4310002), National Science Foundation (U.S.). Atmospheric Chemistry program (grant no. AGS-1559607), National Science Foundation (U.S.). Atmospheric Chemistry program (grant no. AGS-1558966), Fundação de Amparo à Pesquisa do Estado do Amazonas, Fundação de Amparo à Pesquisa do Estado de São Paulo, Brazil Scientific Mobility Program, United States. National Oceanic and Atmospheric Administration (grant NA10OAR4310106 (MIT)), National Science Foundation (U.S.), Austrian Science Fund (project no. L518-N20)
- Published
- 2018