17:15 〜 19:15
[AAS11-P14] Impact of vibrationally-excited- and stabilized-Criegee intermediates on the global-scale aerosol formation: Detailed kinetics and sensitivity analysis
キーワード：クリーギー中間体、全球化学輸送モデル、硫酸エアロゾル、反応速度論
Understanding aerosol chemistry is required to address climate change and air pollution. The ozonolysis of alkenes produces vibrationally-excited-Criegee intermediates (vCIs) and carbonyl species. vCIs decompose into OH radicals through unimolecular decomposition or are quenched by bath gases such as N2 and O2, forming stabilized-Criegee intermediates (sCIs). While vCIs contribute to the formation of sulfate aerosol (SO42-(p)) through the reaction of the generated OH and sulfur dioxide (SO2), sCIs are also known to be strong oxidizers of SO2. Several studies evaluated the impact of sCIs on global-scale SO42-(p) formation using chemical transport model (CTM), showcasing maximally ~5% of the total contribution of SO42-(p). Nevertheless, no studies evaluated which CIs, vCIs or sCIs, are more relevant to contribute to the formation of SO42-(p) and other aerosols, which is the main purpose of this study.
The CTM calculations were conducted by the Goddard Earth observing system chemistry model (GEOS-Chem v14.2.3), adding detailed Criegee chemistry, most of which were based on the reaction mechanisms proposed by our previous study (Nakamura et al. Environ. Sci.: Atmos. 2023, 3, 1758-1766). The added chemistry included the reactions of sCIs with SO2, NO2, HNO3, organic acids, H2O, and (H2O)2, as well as the unimolecular decomposition of sCIs. The reactions of the ozonolysis of alkenes were also substituted from the default chemical mechanism defined in GEOS-Chem to the definitions provided by Master Chemical Mechanism. Sensitivity analyses were conducted by slightly changing the rate constants of the targeted reaction schemes. For example, to clarify the sensitivity of SO42-(p) formation caused by the sCIs, all the rate constants of the reactions of sCIs + SO2 were multiplied by 1.1. The results suggested that in highly industrialized regions of China and India, vCIs are dominant for SO42-(p) formation. In contrast, in the Amazon rainforests, the contribution of vCIs and sCIs is almost comparable, indicating the importance of sCIs on aerosol formations in remote sites.
This study was supported by a Grant-in-Aid for Scientific Research (B) from the Japan Society for the Promotion of Science (JSPS; Grant Number JP24K03088).
The CTM calculations were conducted by the Goddard Earth observing system chemistry model (GEOS-Chem v14.2.3), adding detailed Criegee chemistry, most of which were based on the reaction mechanisms proposed by our previous study (Nakamura et al. Environ. Sci.: Atmos. 2023, 3, 1758-1766). The added chemistry included the reactions of sCIs with SO2, NO2, HNO3, organic acids, H2O, and (H2O)2, as well as the unimolecular decomposition of sCIs. The reactions of the ozonolysis of alkenes were also substituted from the default chemical mechanism defined in GEOS-Chem to the definitions provided by Master Chemical Mechanism. Sensitivity analyses were conducted by slightly changing the rate constants of the targeted reaction schemes. For example, to clarify the sensitivity of SO42-(p) formation caused by the sCIs, all the rate constants of the reactions of sCIs + SO2 were multiplied by 1.1. The results suggested that in highly industrialized regions of China and India, vCIs are dominant for SO42-(p) formation. In contrast, in the Amazon rainforests, the contribution of vCIs and sCIs is almost comparable, indicating the importance of sCIs on aerosol formations in remote sites.
This study was supported by a Grant-in-Aid for Scientific Research (B) from the Japan Society for the Promotion of Science (JSPS; Grant Number JP24K03088).