A new model mechanism for atmospheric oxidation of isoprene: global effects on oxidants, nitrogen oxides, organic products, and secondary organic aerosol
A new model mechanism for atmospheric oxidation of isoprene: global effects on oxidants, nitrogen oxides, organic products, and secondary organic aerosol
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DOI：
10.5194/acp-19-9613-2019
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发表时间：
2019-07-31
影响因子：
6.3
通讯作者：
Jacob, Daniel J.
中科院分区：
文献类型：
--
作者：
Bates, Kelvin H.;Jacob, Daniel J.
异戊二烯是排放量最大的非甲烷碳氢化合物，其大气氧化会影响臭氧（O-3）、羟基自由基（OH）、氮氧化物自由基（NOx）、一氧化碳（CO）、氧化和硝化有机化合物以及二次有机气溶胶（SOA）的丰度。我们分析了这些影响，在框模型和全球GEOS-Chem化学运输模型中使用新的减少加州理工学院异戊二烯机制（RCIM）凝聚从最近开发的显式异戊二烯氧化机制。我们发现许多相似之处与以前的全球模型的异戊二烯化学沿着一些重要的差异。适当的会计过氧自由基的异构体分布后，除了OH和O-2异戊二烯的影响，随后的产品分布，特别是减少甲基丙烯醛的产率和增加的能力，分子内氢转移迅速再生OH。整个机制的氢转移反应导致增加OH再循环，导致在低NO条件下的OH比以前的机制更少的消耗。更高的有机硝酸盐产率和更快的叔硝酸盐水解导致更有效的NOx去除异戊二烯和转化为无机硝酸盐。只有20%的异戊二烯衍生的有机硝酸酯（不包括过氧酰基硝酸酯）被化学回收为NOx。从异戊二烯的甲醛的全球产率为22%/碳，并且对NO的敏感性低于以前的机制。乙二醛的总摩尔产率为2%，远低于以前的机制，因为乙二醛前体的沉积和气溶胶吸收。全球异戊二烯SOA的产量约有三分之一来自以下每一种：异戊二烯环氧二醇（IEPDX），有机硝酸酯和四官能化合物。我们发现，从异戊二烯的SOA产量为13%每碳，远高于通常假设的模型和可能抵消SOA的化学损失。我们使用我们的模拟结果，以进一步冷凝RCIM成一个迷你加州理工学院异戊二烯机制（Mini-CIM），以更便宜的实施在大气模型中，总规模（108种，345反应），目前使用的机制。
Atmospheric oxidation of isoprene, the most abundantly emitted non-methane hydrocarbon, affects the abundances of ozone (O-3), the hydroxyl radical (OH), nitrogen oxide radicals (NOx), carbon monoxide (CO), oxygenated and nitrated organic compounds, and secondary organic aerosol (SOA). We analyze these effects in box models and in the global GEOS-Chem chemical transport model using the new reduced Caltech isoprene mechanism (RCIM) condensed from a recently developed explicit isoprene oxidation mechanism. We find many similarities with previous global models of isoprene chemistry along with a number of important differences. Proper accounting of the isomer distribution of peroxy radicals following the addition of OH and O-2 to isoprene influences the subsequent distribution of products, decreasing in particular the yield of methacrolein and increasing the capacity of intramolecular hydrogen shifts to promptly regenerate OH. Hydrogen shift reactions throughout the mechanism lead to increased OH recycling, resulting in less depletion of OH under low-NO conditions than in previous mechanisms. Higher organonitrate yields and faster tertiary nitrate hydrolysis lead to more efficient NOx removal by isoprene and conversion to inorganic nitrate. Only 20% of isoprene-derived organonitrates (excluding peroxyacyl nitrates) are chemically recycled to NOx. The global yield of formaldehyde from isoprene is 22% per carbon and less sensitive to NO than in previous mechanisms. The global molar yield of glyoxal is 2%, much lower than in previous mechanisms because of deposition and aerosol uptake of glyoxal precursors. Global production of isoprene SOA is about one-third from each of the following: isoprene epoxydiols (IEPDX), organonitrates, and tetrafunctional compounds. We find a SOA yield from isoprene of 13% per carbon, much higher than commonly assumed in models and likely offset by SOA chemical loss. We use the results of our simulations to further condense RCIM into a mini Caltech isoprene mechanism (Mini-CIM) for less expensive implementation in atmospheric models, with a total size (108 species, 345 reactions) comparable to currently used mechanisms.