The role of chlorine in global tropospheric chemistry
The role of chlorine in global tropospheric chemistry
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DOI：
10.5194/acp-19-3981-2019
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发表时间：
2019-03
影响因子：
6.3
通讯作者：
Xuan Wang;D. Jacob;S. Eastham;M. Sulprizio;Lei Zhu;Qianjie Chen;B. Alexander;T. Sherwen;M. Ev
中科院分区：
文献类型：
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作者：
Xuan Wang;D. Jacob;S. Eastham;M. Sulprizio;Lei Zhu;Qianjie Chen;B. Alexander;T. Sherwen;M. Ev
抽象的。我们在氧化剂-气溶胶-卤素大气化学的 GEOS-Chem 全球 3-D 模型中对对流层氯进行了全面模拟。该模拟包括通过 HCl 的酸置换和其他非均相过程从海盐气溶胶中动员氯化物的明确计算。还包括对流层氯的其他小来源（燃烧、有机氯、来自平流层的输送）。反应性气相氯 Cl*，包括 Cl、ClO、Cl2、BrCl、ICl、HOCl、ClNO3、ClNO2 和少量物质，是通过 HCl+OH 反应以及海盐气溶胶氯化物非均相转化为 BrCl、ClNO2、Cl2 和 ICl 产生的。该模型成功模拟了观测到的海洋空气中 HCl 的混合比例（北部中纬度地区最高）以及因酸置换而导致的相关 HNO3 减少。它捕获了夜间大陆表面空气中观察到的高 ClNO2 混合比，并将氯归因于从海盐气溶胶中挥发出来的 HCl，并在被细气溶胶吸收后输送到内陆。该模型成功模拟了从飞机上测量的 HCl 的垂直剖面，其中大陆边界层的增强可以再次在很大程度上通过海洋源的内陆运输来解释。它无法重现冬季飞机活动中测量的边界层 Cl2 混合比（白天为 1-5 ppt，夜间较低）；该模型在夜间过高，这可能是由于 ClNO2+Cl- 反应速率的不确定性，但我们无法解释白天观察到的高 Cl2。模型中 Cl 原子的全球平均对流层浓度为 620 cm−3，贡献了全球甲烷氧化的 1.0%、乙烷的 20%、丙烷的 14% 和甲醇的 4%。氯化学主要通过 HOBr+Cl- 反应将全球平均对流层 BrO 增加 85%，并通过相关的溴自由基化学将全球对流层臭氧负担减少 7%，将 OH 负担减少 3%。 ClNO2 化学物质导致冬季污染大陆上的臭氧增加高达 8 ppb。
Abstract. We present a comprehensive simulation of tropospheric chlorine within the GEOS-Chem global 3-D model of oxidant–aerosol–halogen atmospheric chemistry. The simulation includes explicit accounting of chloride mobilization from sea salt aerosol by acid displacement of HCl and by other heterogeneous processes. Additional small sources of tropospheric chlorine (combustion, organochlorines, transport from stratosphere) are also included. Reactive gas-phase chlorine Cl*, including Cl, ClO, Cl2, BrCl, ICl, HOCl, ClNO3, ClNO2, and minor species, is produced by the HCl+OH reaction and by heterogeneous conversion of sea salt aerosol chloride to BrCl, ClNO2, Cl2, and ICl. The model successfully simulates the observed mixing ratios of HCl in marine air (highest at northern midlatitudes) and the associated HNO3 decrease from acid displacement. It captures the high ClNO2 mixing ratios observed in continental surface air at night and attributes the chlorine to HCl volatilized from sea salt aerosol and transported inland following uptake by fine aerosol. The model successfully simulates the vertical profiles of HCl measured from aircraft, where enhancements in the continental boundary layer can again be largely explained by transport inland of the marine source. It does not reproduce the boundary layer Cl2 mixing ratios measured in the WINTER aircraft campaign (1–5 ppt in the daytime, low at night); the model is too high at night, which could be due to uncertainty in the rate of the ClNO2+Cl- reaction, but we have no explanation for the high observed Cl2 in daytime. The global mean tropospheric concentration of Cl atoms in the model is 620 cm−3 and contributes 1.0 % of the global oxidation of methane, 20 % of ethane, 14 % of propane, and 4 % of methanol. Chlorine chemistry increases global mean tropospheric BrO by 85 %, mainly through the HOBr+Cl- reaction, and decreases global burdens of tropospheric ozone by 7 % and OH by 3 % through the associated bromine radical chemistry. ClNO2 chemistry drives increases in ozone of up to 8 ppb over polluted continents in winter.