基于PAM模拟的溴自由基氧化大气汞的二阶转化机制研究

大气氧化是造成汞由大气迁移至地表环境的关键过程，而溴自由基(Br·)则是引起全球大气汞氧化的主要氧化剂。Br·氧化大气汞的路径未完全知晓，及其反应速率不确定性较大是制约汞形态转化机制理解的核心因素。理论计算研究指出NO2·与HO2·可取代Br·进行第二阶的汞氧化过程，但其对形态汞转化的影响仍缺乏系统研究。针对以上科学问题，本研究拟在上海崇明岛进行形态汞与溴、NO2·、HO2·等观测分析，明确Br·、NO2·与HO2·等对形态汞的影响规律；结合PAM流动管模拟实验与箱式模型模拟等方式，探讨Br·氧化Hg0的二阶转化机制并揭示NO2·与HO2·的作用机制；改进GEOS-Chem模式模拟大气汞行为，阐明Br·氧化对大气汞迁移沉降等行为的影响。本研究成果，将为理解大气汞转化与去除提供理论和技术支撑，对推动我国大气强氧化性氛围下履行国际汞公约具有重要实际应用价值。

Atmosphere oxidation is the crucial process for mercury migration from air to land surface, in which bromine radical (Br·) is the primary oxidant initiated the global atmospheric mercury oxidation behavior. However, the specific pathway of mercury oxidation initiated by Br· was still not well known, there were also many uncertainties in its reaction rates. Both of them were the core factors which limit understanding of mercury transformation mechanism. Additionally, theoretical calculation researches suggested that NO2· and HO2·radicals can replace Br· radical further oxidize mercury in the second step oxidation process, but there still lacks systematical research of the influence on speciated mercury transformation from NO2· and HO2·. To solve these scientific problems, this application proposes to carry out a comprehensive investigation of speciated mercury, bromine, NO2· and HO2·radicals at Chongming Island Observation station, Shanghai, to understand the dynamic effects on speciated mercury variations caused from Br·, NO2· and HO2·radicals. Combined these observations with PAM (potential air mass) reactor simulation experiments, as well as atmospheric chemical box model simulation, some results will be given: the specific two-step reaction mechanism for Br· oxidizing Hg0, and the relative influence from NO2· and HO2·radicals. Finally, the mercury chemistry module of GEOS-Chem model will be updated via the mechanism of mercury oxidation caused by Br∙, and based on the model simulation and prediction, the effects on the fates of migration and deposition of mercury in atmosphere from of Br· oxidation process will be discussed. The results of this project will not only provide theoretical and technical support for understanding of the conversion and removal behaviors of atmospheric mercury, but also exist important practical application value for promoting the implementation of the international convention on mercury, especially under the background of strong oxidizing atmosphere environment in China.