期刊
ENVIRONMENTAL SCIENCE & TECHNOLOGY
卷 56, 期 22, 页码 15337-15346出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.2c04030
关键词
biogenic volatile organic compounds; secondary organic aerosol; nitrate radical; highly oxidized molecules; dinitrate
资金
- National Natural Science Foundation of China [AGS-1953905]
- Science and Technology Foundation of Guizhou Provincial Department of Education, China [CHE-2002413]
- U.S. National Science Foundation
- UC Riverside Faculty Development Fellowship
- [42120104007]
- [KY[2021]014]
This study investigates the nighttime oxidation and secondary organic aerosol (SOA) formation mechanisms of limonene. The results show that limonene can be oxidized rapidly by ozone and nitrate radicals, leading to the formation of highly oxidized organic nitrates and nitrooxy peroxy radicals. Quantum chemical calculations and kinetic simulations reveal the main oxidation pathways, which explain the observed highly oxidized organic nitrates. The study also demonstrates the relevance of these mechanisms in the formation of organic aerosols in the nighttime atmosphere.
Limonene is an abundant monoterpene released into the atmosphere via biogenic emissions and biomass burning. However, the atmospheric oxidation and secondary organic aerosol (SOA) formation mechanisms of limonene, especially during nighttime, remain largely understudied. In this work, limonene was oxidized synergistically by ozone (O3) and nitrate radicals (NO3) in a flow tube reactor and a continuous flow stirred tank reactor. Upon oxidation, many highly oxidized organic nitrates and nitrooxy peroxy radicals (RO2) were observed in the gas phase within 1 min. Combining quantum chemical calculations with kinetic simulations, we found that the primary nitrooxy RO2 (C10H16NO5) through NO3 addition at the more substituted endocyclic double bond and at the exocyclic double bond (previously considered as minor pathways) can undergo autoxidation with rate constants of around 0.02 and 20 s-1 at 298 K, respectively. These pathways could explain a major portion of the observed highly oxidized organic nitrates. In the SOA, highly oxidized mono-and dinitrates (e.g., C10H17NO7-8 and C10H16,18N2O8-10) make up a significant contribution, highlighting nitrooxy RO2 autoxidation and sequential NO3 oxidation of limonene. The same organic nitrates are also observed in ambient aerosol during biomass burning and nighttime in the southeastern United States. Therefore, the present work provides new insights into the nighttime oxidation of limonene and SOA formation in the atmosphere.
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