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© 2016. This work is published under http://creativecommons.org/licenses/by/3.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

Recent laboratory studies suggest that secondary organic aerosol (SOA) formation rates are higher than assumed in current models. There is also evidence that SOA removal by dry and wet deposition occurs more efficiently than some current models suggest and that photolysis and heterogeneous oxidation may be important (but currently ignored) SOA sinks. Here, we have updated the global GEOS-Chem model to include this new information on formation (i.e., wall-corrected yields and emissions of semi-volatile and intermediate volatility organic compounds) and on removal processes (photolysis and heterogeneous oxidation). We compare simulated SOA from various model configurations against ground, aircraft and satellite measurements to assess the extent to which these improved representations of SOA formation and removal processes are consistent with observed characteristics of the SOA distribution. The updated model presents a more dynamic picture of the life cycle of atmospheric SOA, with production rates 3.9 times higher and sinks a factor of 3.6 more efficient than in the base model. In particular, the updated model predicts larger SOA concentrations in the boundary layer and lower concentrations in the upper troposphere, leading to better agreement with surface and aircraft measurements of organic aerosol compared to the base model. Our analysis thus suggests that the long-standing discrepancy in model predictions of the vertical SOA distribution can now be resolved, at least in part, by a stronger source and stronger sinks leading to a shorter lifetime. The predicted global SOA burden in the updated model is 0.88 Tg and the corresponding direct radiative effect at top of the atmosphere is -0.33 W m-2, which is comparable to recent model estimates constrained by observations. The updated model predicts a population-weighed global mean surface SOA concentration that is a factor of 2 higher than in the base model, suggesting the need for a reanalysis of the contribution of SOA to PM pollution-related human health effects. The potential importance of our estimates highlights the need for more extensive field and laboratory studies focused on characterizing organic aerosol removal mechanisms and rates.

Details

Title
Rethinking the global secondary organic aerosol (SOA) budget: stronger production, faster removal, shorter lifetime
Author
Hodzic, Alma 1 ; Kasibhatla, Prasad S 2   VIAFID ORCID Logo  ; Jo, Duseong S 3 ; Cappa, Christopher D 4   VIAFID ORCID Logo  ; Jimenez, Jose L 5   VIAFID ORCID Logo  ; Madronich, Sasha 1 ; Park, Rokjin J 3   VIAFID ORCID Logo 

 National Center for Atmospheric Research, Boulder, CO, USA 
 Nicholas School of the Environment, Duke University, Durham, USA 
 School of Earth and Environmental Science, Seoul National University, Seoul, Republic of Korea 
 Department of Civil and Environmental Engineering, University of California, Davis, CA, USA 
 Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA 
Pages
7917-7941
Publication year
2016
Publication date
2016
Publisher
Copernicus GmbH
ISSN
16807316
e-ISSN
16807324
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2414531073
Copyright
© 2016. This work is published under http://creativecommons.org/licenses/by/3.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.