Abstract：
Alkene ozonolysis can produce stabilized Criegee intermediates (SCIs), which play a key role in oligomers\' formation. Though styrene and isoprene coexist in the ambient atmosphere as important anthropogenic and biogenic secondary organic aerosol (SOA) precursors, respectively, their cross-reactions have not received attention. This study investigated the interactions of SCIs from styrene and isoprene ozonolysis for the first time. The high-resolution Orbitrap mass spectrometer was used to determine the unique ion mass spectra of the isoprene-styrene-O3 mixture. The results show that the signal intensities of new ions account for >8.4% of total ions in the mass spectra of the styrene-isoprene-O3 mixed system. Styrene and isoprene ozonolysis can produce characteristic C7-SCI and C4-SCI, respectively. C7-SCI and C4-SCI can be involved in the cross-reactions, and the results of tandem mass spectra directly confirmed both C7-SCI and C4-SCI as chain units. The O/C and H/C ratios of cross-products are in the range of 0.38-1.07 and 1.00-1.50, respectively, which are consistent with cross-reaction products. Adding a C7-SCI unit reduces the oligomer\'s volatility by 1.3-1.4 orders of magnitude lower than adding a C4-SCI unit. Thus, C4-SCI can compete with C7-SCI to react with styrene-derived RO2/RC(O)OH to produce more volatile cross-products, while the less volatile cross-products can be formed when isoprene-derived RO2/RC(O)OH reacted with C7-SCI instead of C4-SCI. The SOA yield of the mixed system is lower than that of the single styrene-O3 system but higher than that of the single isoprene-O3 system. Ambient particles were also collected, and 5 possible SCI-related cross-products were identified. This study illustrates the effects of SCI-related cross-reactions on SOA components and physicochemical properties, providing a basis for future research on SCI-related cross-reactions that frequently occur in the ambient atmosphere.
摘要：
烯烃臭氧分解可以产生稳定的Criegee中间体（SCI），在低聚物的形成中起关键作用。尽管苯乙烯和异戊二烯作为重要的人为和生物次级有机气溶胶（SOA）前体在环境大气中共存，分别,他们的交叉反应没有引起注意。这项研究首次研究了苯乙烯和异戊二烯臭氧分解的SCIs的相互作用。高分辨率Orbitrap质谱仪用于确定异戊二烯-苯乙烯-O3混合物的独特离子质谱。结果表明，在苯乙烯-异戊二烯-O3混合体系的质谱中，新离子的信号强度占总离子的8.4％以上。苯乙烯和异戊二烯臭氧分解可以分别产生特征性的C7-SCI和C4-SCI。C7-SCI和C4-SCI可以参与交叉反应，串联质谱的结果直接证实了C7-SCI和C4-SCI均为链单元。交叉产品的O/C和H/C比分别在0.38-1.07和1.00-1.50范围内，与交叉反应产物一致。添加C7-SCI单位比添加C4-SCI单位降低了1.3-1.4个数量级。因此，C4-SCI可以与C7-SCI竞争，与苯乙烯衍生的RO2/RC（O）OH反应，产生更多的挥发性交叉产物，而当异戊二烯衍生的RO2/RC（O）OH与C7-SCI代替C4-SCI反应时，可以形成挥发性较低的交叉产物。混合体系的SOA产率低于单一苯乙烯-O3体系，但高于单一异戊二烯-O3体系。还收集了环境颗粒，并确定了5种可能的SCI相关交叉产品。这项研究说明了SCI相关的交叉反应对SOA成分和理化性质的影响，为未来研究环境大气中频繁发生的SCI相关交叉反应提供基础。
