Comparison of the Yield and Chemical Composition of Secondary Organic Aerosol Generated from the OH and Cl Oxidation of Decamethylcyclopentasiloxane
Comparison of the Yield and Chemical Composition of Secondary Organic Aerosol Generated from the OH and Cl Oxidation of Decamethylcyclopentasiloxane
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DOI：
10.1021/acsearthspacechem.2c00304
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发表时间：
2023-01-05
影响因子：
3.4
通讯作者：
Lambe, Andrew T.
中科院分区：
文献类型：
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作者：
Avery, Anita M.;Alton, Mitchell W.;Lambe, Andrew T.
工业过程和消费品排放的环状挥发性甲基硅氧烷（cVMS）通常是占用空间中挥发性有机化合物（VOC）的主要负担。cVMS可能有助于氧化VOC和二次有机气溶胶（SOA）的形成后，在室内和室外源区域的气相自由基氧化。最近的几项研究检查了十甲基环戊硅氧烷（D5）暴露于羟基自由基（OH）后形成SOA的可能性，发现该反应在氧化老化多天后以高产率生成SOA。氯原子（Cl）可能会与OH竞争的D5的氧化损失在室内和室外的源区域与活跃的氯化学，但SOA的形成潜力的D5 + Cl反应还没有研究。在这里，我们表征了在干燥[相对湿度（RH）< 5%]和潮湿（RH = 40%）条件下在氧化流动反应器（OFR）中由D5的Cl氧化产生的SOA的产率和化学组成，并将结果与由D5的OH氧化产生的SOA的产率和组成进行比较。使用范围分别为1.1 x 1012 - 8.2 x 1012 cm-3 s和1.6 x 1010 - 1.6 x 1012 cm-3 s的综合OH和Cl暴露（OHexp和Clexp）氧化D5。像OH，Cl促进多步SOA氧化老化的OFR条件的范围内进行了研究，与最大SOA的质量收率为1.5和1.3以下的OH和Cl氧化D5在潮湿的条件下获得。这些结果表明，室内和室外的源区域，显着影响氯化学可能会提高大气SOA的形成潜力的D5。
Cyclic volatile methyl siloxanes (cVMS) that are emitted from industrial processes and consumer products often dominate the burden of volatile organic compounds (VOCs) in occupied spaces. cVMS may contribute to oxygenated VOC and secondary organic aerosol (SOA) formation following oxidation by gas-phase radicals in both indoor and outdoor source regions. Several recent studies examined the SOA formation potential of decamethylcyclopentasiloxane (D5) following exposure to hydroxyl radicals (OH) and found that this reaction generates SOA in high yield following multiple days of oxidative aging. Chlorine atoms (Cl) may compete with OH for the oxidative loss of D5 in indoor and outdoor source regions with active chlorine chemistry, but the SOA formation potential of D5 + Cl reactions has not been studied. Here, we characterized the yield and chemical composition of SOA generated from Cl oxidation of D5 in an oxidation flow reactor (OFR) under dry [relative humidity (RH) < 5%] and humid (RH = 40%) conditions and compared results to the yield and composition of SOA generated from OH oxidation of D5. D5 was oxidized using integrated OH and Cl exposures (OHexp and Clexp) ranging from 1.1 x 1012 to 8.2 x 1012 cm-3 s and from 1.6 x 1010 to 1.6 x 1012 cm-3 s, respectively. Like OH, Cl facilitated multistep SOA oxidative aging over the range of OFR conditions that were studied, with maximum SOA mass yields of 1.5 and 1.3 obtained following OH and Cl oxidation of D5 under humid conditions. These results suggest that indoor and outdoor source regions that are significantly influenced by chlorine chemistry may enhance the atmospheric SOA formation potential of D5.