Isotopic constraints on the role of hypohalous acids in sulfate aerosol formation in the remote marine boundary layer
Isotopic constraints on the role of hypohalous acids in sulfate aerosol formation in the remote marine boundary layer
复制标题
同位素限制次卤酸在遥远海洋边界层硫酸盐气溶胶形成中的作用
DOI：
10.5194/acp-16-11433-2016
复制
发表时间：
2016-09-14
影响因子：
6.3
通讯作者：
Alexander, Becky
中科院分区：
文献类型：
--
作者：
Chen, Qianjie;Geng, Lei;Alexander, Becky
硫酸盐是全球大气气溶胶的重要组成部分，部分补偿了工业时期温室气体引起的变暖。自工业化前时代以来，气溶胶的直接和间接辐射强迫的大小在气候模型中是一个很大的不确定性，这在很大程度上归因于工业化前环境的不确定性。在这里，我们报告了春季和夏季在偏远海洋边界层（MBL）收集的硫酸盐气溶胶的氧同位素组成（Delta O-17）的观测结果，以评估原始环境中硫酸盐的产生机制。对观测结果的模型辅助分析表明，MBL 中 33-50% 的硫酸盐是通过次卤酸 (HOX = HOBr + HOCl) 氧化形成的，由于反应速率的不确定性（主要是由于活性卤素浓度的不确定性），这种生产机制通常被排除在大规模模型中。根据估计的 HOX 氧化形成的硫酸盐比例，我们进一步估计，春季和夏季偏远 MBL 中每日平均 HOX 混合比例约为万亿分之 0.01-0.1 (ppt = pmol/mol)，足以解释观测结果。
Sulfate is an important component of global atmospheric aerosol, and has partially compensated for greenhouse gas-induced warming during the industrial period. The magnitude of direct and indirect radiative forcing of aerosols since preindustrial times is a large uncertainty in climate models, which has been attributed largely to uncertainties in the preindustrial environment. Here, we report observations of the oxygen isotopic composition (Delta O-17) of sulfate aerosol collected in the remote marine boundary layer (MBL) in spring and summer in order to evaluate sulfate production mechanisms in pristine-like environments. Model-aided analysis of the observations suggests that 33-50% of sulfate in the MBL is formed via oxidation by hypohalous acids (HOX = HOBr + HOCl), a production mechanism typically excluded in large-scale models due to uncertainties in the reaction rates, which are due mainly to uncertainties in reactive halogen concentrations. Based on the estimated fraction of sulfate formed via HOX oxidation, we further estimate that daily-averaged HOX mixing ratios on the order of 0.01-0.1 parts per trillion (ppt = pmol/mol) in the remote MBL during spring and summer are sufficient to explain the observations.