Radical loss in the atmosphere from Cu-Fe redox coupling in aerosols
Radical loss in the atmosphere from Cu-Fe redox coupling in aerosols
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DOI：
10.5194/acp-13-509-2013
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发表时间：
2012-10
影响因子：
6.3
通讯作者：
J. Mao;S. Fan;D. Jacob;K. Travis
中科院分区：
文献类型：
--
作者：
J. Mao;S. Fan;D. Jacob;K. Travis
抽象的。过氧化氢自由基(HO2)是OH和对流层臭氧的主要前体。OH是大气的主要氧化剂，而对流层臭氧是一种重要的地表污染物和温室气体。大气化学的标准气相模型倾向于高估观测到的HO2浓度，这暂时被归因于气溶胶颗粒的异质吸收。一般认为，气溶胶对HO2的吸收涉及转化为HO2，但作为HO2汇的效果有限，因为H2O2可以光解生成OH，并从那里重新生成HO2。对HO2和H2O2的联合大气观测表明，气溶胶吸收HO2实际上可能不会产生H2O2。本文提出了一种过渡金属离子Cu(I)/Cu(II)和Fe(II)/Fe(III)在气溶胶中快速转化HO2为H2O的催化机理。潜在的HO2吸收和转化为H2O显著影响了全球模式对对流层OH、臭氧、一氧化碳(CO)和其他物种的预测，改善了与GEOS-Chem模式中的观测结果的对比。它通过对主要温室气体，包括甲烷和氢氟碳化合物(HFCs)的化学收支的影响，代表了以前未被认识到的气溶胶的正辐射强迫。
Abstract. The hydroperoxyl radical (HO2) is a major precursor of OH and tropospheric ozone. OH is the main atmospheric oxidant, while tropospheric ozone is an important surface pollutant and greenhouse gas. Standard gas-phase models for atmospheric chemistry tend to overestimate observed HO2 concentrations, and this has been tentatively attributed to heterogeneous uptake by aerosol particles. It is generally assumed that HO2 uptake by aerosol involves conversion to H2O2, but this is of limited efficacy as an HO2 sink because H2O2 can photolyze to regenerate OH and from there HO2. Joint atmospheric observations of HO2 and H2O2 suggest that HO2 uptake by aerosols may in fact not produce H2O2. Here we propose a catalytic mechanism involving coupling of the transition metal ions Cu(I)/Cu(II) and Fe(II)/Fe(III) to rapidly convert HO2 to H2O in aqueous aerosols. The implied HO2 uptake and conversion to H2O significantly affects global model predictions of tropospheric OH, ozone, carbon monoxide (CO) and other species, improving comparisons to observations in the GEOS-Chem model. It represents a previously unrecognized positive radiative forcing of aerosols through the effects on the chemical budgets of major greenhouse gases including methane and hydrofluorocarbons (HFCs).