Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 54, Issue 7, Pages 3861-3870Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.9b07051
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Funding
- U.S. Department of Energy (DOE) Office of Science, Office of Biological and Environmental Research, and Atmospheric Systems Research (ASR) program
- U.S. DOE, Office of Science, Office of Biological and Environmental Research through the Early Career Research Program
- Office of Biological and Environmental Research
- DOE [DE-AC05-76RL01830]
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Secondary organic aerosol (SOA) accounts for a large fraction of the tropospheric particulate matter. Although SOA production rates and mechanisms have been extensively investigated, loss pathways remain uncertain. Most large-scale chemistry and transport models account for mechanical deposition of SOA but not chemical losses such as photolysis. There is also a paucity of laboratory measurements of SOA photolysis, which limits how well photolytic losses can be modeled. Here, we show, through a combined experimental and modeling approach, that photolytic loss of SOA mass significantly alters SOA budget predictions. Using environmental chamber experiments at variable relative humidity between 0 and 60%, we find that SOA produced from several biogenic volatile organic compounds undergoes photolysis-induced mass loss at rates between 0 and 2.2 +/- 0.4% of nitrogen dioxide (NO2) photolysis, equivalent to average atmospheric lifetimes as short as 10 h. We incorporate our photolysis rates into a regional chemical transport model to test the sensitivity of predicted SOA mass concentrations to photolytic losses. The addition of photolysis causes a similar to 50% reduction in biogenic SOA loadings over the Amazon, indicating that photolysis exerts a substantial control over the atmospheric SOA lifetime, with a likely dependence upon the SOA molecular composition and thus production mechanisms.
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