A global model of tropospheric chlorine chemistry: Organic versus inorganic sources and impact on methane oxidation
A global model of tropospheric chlorine chemistry: Organic versus inorganic sources and impact on methane oxidation
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DOI：
10.1002/2016jd025756
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发表时间：
2016-12-16
影响因子：
4.4
通讯作者：
von Glasow, Roland
中科院分区：
文献类型：
--
作者：
Hossaini, Ryan;Chipperfield, Martyn P.;von Glasow, Roland
氯原子（Cl）对地球对流层中的碳氢化合物具有高度反应性，包括温室气体甲烷（CH 4）。然而，由于对流层氯浓度（[Cl]）的不确定性接近2个数量级，因此区域和全球Cl的CH 4汇难以量化。在这里，我们描述了一个详细的对流层氯计划的TOMCAT化学传输模式。该模型包括对流层无机氯（Cly）的几个来源，包括（i）天然（CH 3Cl，CHBr 2Cl，CH 2BrCl和CHBrCl 2）和人为（CH 2Cl 2，CHCl 3，C2Cl 4，C2 HCl 3和CH 2ClCH 2Cl）来源的氯烃的氧化和（ii）海盐气溶胶脱氯。模拟进行量化对流层[Cl]，重点是海洋边界层，并量化Cl原子CH 4氧化的全球意义。与观测结果一致，模拟的表面水平的氯化氢（HCl），最丰富的氯-y水库，达到十亿分之几（ppb）的污染沿海/大陆地区，与亚ppb的水平在更偏远的地区典型。模拟的年平均表面[Cl]表现出很大的空间变异性，在受污染的北方半球，其最大水平通常在1- 5x 10（4）原子cm（-3）的范围内。氯碳氧化提供了一个对流层Cly源，其浓度高达4320 Gg Cl/yr，在大面积区域维持< 0.1至0.5 x 10（3）原子cm（-3）的背景表面[Cl]。在全球范围内，我们估计对流层甲烷汇类似于12-13 Tg CH 4/年，由于CH 4 + Cl反应（类似于总CH 4氧化的2.5%）。预计会产生更大的区域效应，在某些地点，Cl占边界层CH 4氧化总量的10%至> 20%。
Chlorine atoms (Cl) are highly reactive toward hydrocarbons in the Earth's troposphere, including the greenhouse gas methane (CH4). However, the regional and global CH4 sink from Cl is poorly quantified as tropospheric Cl concentrations ([Cl]) are uncertain by similar to 2 orders of magnitude. Here we describe the addition of a detailed tropospheric chlorine scheme to the TOMCAT chemical transport model. The model includes several sources of tropospheric inorganic chlorine (Cly), including (i) the oxidation of chlorocarbons of natural (CH3Cl, CHBr2Cl, CH2BrCl, and CHBrCl2) and anthropogenic ( CH2Cl2, CHCl3, C2Cl4, C2HCl3, and CH2ClCH2Cl) origin and ( ii) sea-salt aerosol dechlorination. Simulations were performed to quantify tropospheric [Cl], with a focus on the marine boundary layer, and quantify the global significance of Cl atom CH4 oxidation. In agreement with observations, simulated surface levels of hydrogen chloride (HCl), the most abundant Cl-y reservoir, reach several parts per billion (ppb) over polluted coastal/continental regions, with sub-ppb levels typical in more remote regions. Modeled annual mean surface [Cl] exhibits large spatial variability with the largest levels, typically in the range of 1-5x10(4) atoms cm(-3), in the polluted northern hemisphere. Chlorocarbon oxidation provides a tropospheric Cly source of up to similar to 4320 Gg Cl/yr, sustaining a background surface [Cl] of < 0.1 to 0.5 x 10(3) atoms cm(-3) over large areas. Globally, we estimate a tropospheric methane sink of similar to 12-13 Tg CH4/yr due the CH4 + Cl reaction (similar to 2.5% of total CH4 oxidation). Larger regional effects are predicted, with Cl accounting for similar to 10 to > 20% of total boundary layer CH4 oxidation in some locations.