Leibniz-Institute for Tropospheric Research, Permoserstr. 15, D-04318 Leipzig, Germany.
Faraday Discuss. 2013;165:237-59. doi: 10.1039/c3fd00042g.
Recent studies show that isoprene-derived organosulfates are an important fraction of ambient secondary organic aerosol (SOA), adding up to 20% to the organic mass. Organosulfates with m/z of 199 and 183 relating to C4 compounds are found in ambient and laboratory generated SOA and a sulfate radical induced oxidation of methacrolein (MACR) and methyl vinyl ketone (MVK) has been shown to be a possible formation mechanism. In the present study, experiments on the sulfate radical-induced oxidation of methacrolein and methyl vinyl ketone were performed in bulk aqueous phase, as well as in an aerosol chamber, and finally compared with ambient PM10 samples collected at a rural East German village during the summer 2008, to investigate their relevance in aqueous phase SOA formation. Samples from aqueous phase experiments and extracts from filters were analysed with UPLC/(-)ESI-IMS-QTOFMS. All the samples showed the abundance of highly oxidised organosulfates with m/z 153, 155, 167, 183 and 199 corresponding to the species found in ambient particle samples. In the bulk phase studies with laser-induced sulfate radical formation, the signal intensities increased with increasing number of laser pulses, indicating the sulfate radical-induced formation of these organosulfates. Additionally, the chamber experiments showed a particle mass growth of about 10 microg m(-3) and 4 microg m(-3) for experiments on the reactive uptake of MACR and MVK with a sulfate radical precursor (K2S2O8) in the seed particles. Correlations of the C2 to C5 organosulfate species (including the m/z 215, C5H11O7S-), detected in the ambient samples were found to be very strong (r > 0.8), indicating that these compounds are formed from similar mechanisms and under equal environmental conditions. This study shows that sulfate radical-induced oxidation in the aqueous particle phase provides a reasonable explanation for the formation of these organosulfates from methacrolein and methyl vinyl ketone.
最近的研究表明，异戊二烯衍生的有机硫酸盐是环境中二次有机气溶胶（SOA）的一个重要组成部分，占有机物质的 20%。在环境和实验室生成的 SOA 中发现了与 C4 化合物相关的 m/z 为 199 和 183 的有机硫酸盐，并且已经表明硫酸根自由基诱导的甲基丙烯醛（MACR）和甲基乙烯基酮（MVK）的氧化是一种可能的形成机制。在本研究中，在 bulk aqueous phase 和气溶胶室中进行了硫酸根自由基诱导的甲基丙烯醛和甲基乙烯基酮氧化实验，最后与 2008 年夏季在德国东部一个农村地区采集的环境 PM10 样本进行了比较，以研究它们在水相 SOA 形成中的相关性。对水相实验样品和过滤器提取物进行了 UPLC/（-）ESI-IMS-QTOFMS 分析。所有样品都显示出高度氧化的有机硫酸盐 m/z 153、155、167、183 和 199 的丰度，这些物质与环境颗粒物样品中发现的物质相对应。在 bulk phase 实验中，通过激光诱导形成硫酸根自由基，随着激光脉冲数的增加，信号强度增加，表明这些有机硫酸盐是由硫酸根自由基诱导形成的。此外，在 chamber 实验中，在有硫酸盐自由基前体（K2S2O8）的情况下，实验中 MACR 和 MVK 的反应性吸收使粒子质量分别增长了约 10 μg m(-3) 和 4 μg m(-3)。在环境样品中检测到的 C2 到 C5 有机硫酸盐物种（包括 m/z 215、C5H11O7S-）之间的相关性非常强（r > 0.8），表明这些化合物是由类似的机制在相同的环境条件下形成的。本研究表明，在水相颗粒相中硫酸根自由基的诱导氧化为甲基丙烯醛和甲基乙烯基酮形成这些有机硫酸盐提供了合理的解释。
