Assessing the Potential for Diol and Hydroxy Sulfate Ester Formation from the Reaction of Epoxides in Tropospheric Aerosols
Assessing the Potential for Diol and Hydroxy Sulfate Ester Formation from the Reaction of Epoxides in Tropospheric Aerosols
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DOI：
10.1021/es8029076
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发表时间：
2009-03-01
影响因子：
11.4
通讯作者：
Elrod, Matthew J.
中科院分区：
文献类型：
--
作者：
Minerath, Emily C.;Elrod, Matthew J.
多元醇和硫酸酯最近已被确定在二次有机气溶胶（SOA）中形成的生物烃在实验室和环境大气条件下的光氧化。在本研究中，环氧化合物在SOA中形成二醇和羟基硫酸酯的反应的潜在作用进行了探索。核磁共振方法被用来监测一些简单的环氧化物的环氧化物水解反应的本体反应动力学。在不同的酸浓度下进行实验，以确认酸催化速率顺序，并确定在气溶胶中的这种反应的二级速率常数，在先前研究的实验室条件下测量的速率和环境大气条件下。常数系统地依赖于环氧环的碳取代性质，叔环氧化物的特点是最大的速率常数。观察到羟基硫酸盐产率线性依赖于总硫酸盐浓度，在高硫酸盐浓度下观察到产率高达30%。由于所观察到的速率常数的大值，这些反应预计是有效的，即使是大多数中和对流层SOA，更不用说更酸性的SOA颗粒先前在实验室中研究的环氧化物水解机制实验。因此，似乎是一个动力学上可行的路线形成的二醇和羟基硫酸酯中观察到的SOA导致的生物烃的光氧化。
Polyols and sulfate esters have recently been identified in the secondary organic aerosol (SOA) formed in the photooxidation of biogenic hydrocarbons both in the laboratory and under ambient atmospheric conditions. In the present study, the potential role of the reactions of epoxides in SOA to form diols and hydroxy sulfate esters is explored. Nuclear magnetic resonance methods were used to monitor the bulk reaction kinetics of the epoxide hydrolysis reactions for a number of simple epoxides. The experiments were carried out at various acid concentrations in order to confirm the acid-catalysis rate order and to determine the second-order rate constants for such reactions in aerosols under the previously studied laboratory conditions The measured rate and under ambient atmospheric conditions. constants depended systematically on the carbon substitution nature of the epoxide ring, with the tertiary epoxides characterized by the largest rate constants. The hydroxy sulfate yield was observed to depend linearly on the total sulfate concentration, with yields as high as 30% observed at high sulfate concentrations. Due to the large values of the observed rate constants, these reactions are expected to be efficient even for mostly neutralized tropospheric SOA, let alone the much more acidic SOA particles previously studied in laboratory the epoxide hydrolysis mechanism experiments. Therefore, appears to be a kinetically feasible route to the formation of the diols and hydroxy sulfate esters observed in the SOA resulting from the photooxidation of biogenic hydrocarbons.