Kinetics and Products of Heterogeneous Hydroxyl Radical Oxidation of Isoprene Epoxydiol-Derived Secondary Organic Aerosol
Kinetics and Products of Heterogeneous Hydroxyl Radical Oxidation of Isoprene Epoxydiol-Derived Secondary Organic Aerosol
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DOI：
10.1021/acsearthspacechem.3c00073
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发表时间：
2023-09
影响因子：
3.4
通讯作者：
Jin Yan;Yue Zhang;Yuzhi Chen;N. C. Armstrong;Nicolas A. Buchenau;Ziying Lei;Yao Xiao;Zhenfa Zhang;A. Lambe;M. N. Chan;Barbara J. Turpin;A. Gold;A. Ault;J. Surratt
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文献类型：
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作者：
Jin Yan;Yue Zhang;Yuzhi Chen;N. C. Armstrong;Nicolas A. Buchenau;Ziying Lei;Yao Xiao;Zhenfa Zhang;A. Lambe;M. N. Chan;Barbara J. Turpin;A. Gold;A. Ault;J. Surratt
异戊二烯环氧二醇衍生二次有机气溶胶(IEPOX-SOA)的非均相氧自由基(·OH)氧化是改变其化学组成的重要老化过程。最近的研究表明，非均相·OH氧化可以老化单组分颗粒甲基四氢呋喃硫酸盐(MTS)，导致∼55%的质量损失。然而，我们最近对新生成的IEPOX-SOA颗粒混合物的研究表明，通过高阶低聚物的碎裂，可以延长完整的IEPOX-SOA混合物对抗非均相·OH氧化的寿命。已发表的研究表明，IEPOX-SOA的非均相·OH氧化可能以不同的速率影响有机大气气溶胶的收支，这取决于气溶胶的化学组成。然而，IEPOX-SOA颗粒混合物的非均相·OH氧化动力学尚未见报道。在这里，我们在潮湿的条件下(相对湿度∼57%)将新鲜生成的IEPOX-SOA颗粒暴露于·OH的非均相氧化中，老化时间为0-15个大气压当量天数，得到有效的非均相·OH速率系数(KOH)为2.64±0.4×10-13cm3分子-1s-1。而未氧化的IEPOX-SOA颗粒有机物的44%在整个老化过程中被消耗，而在老化的最初10天中只消耗了<；7%。通过分子水平的化学分析，我们确定低聚物的消耗速度(快2-4倍)比单体快。气溶胶物理化学性质分析表明，IEPOX-SOA具有核-壳结构，且随着·OH的氧化，壳层变薄。综上所述，本研究表明IEPOX-SOA颗粒的非均相·OH氧化是一个动态过程，气溶胶的化学成分和物理化学性质在其中起着重要的作用。
Heterogeneous hydroxyl radical (•OH) oxidation is an important aging process for isoprene epoxydiol-derived secondary organic aerosol (IEPOX-SOA) that alters its chemical composition. It was recently demonstrated that heterogeneous•OH oxidation can age single-component particulate methyltetrol sulfates (MTSs), causing ∼55% of the SOA mass loss. However, our most recent study of freshly generated IEPOX-SOA particulate mixtures suggests that the lifetime of the complete IEPOX-SOA mixture against heterogeneous•OH oxidation can be prolonged through the fragmentation of higher-order oligomers. Published studies suggest that the heterogeneous•OH oxidation of IEPOX-SOA could affect the organic atmospheric aerosol budget at varying rates, depending on aerosol chemical composition. However, heterogeneous•OH oxidation kinetics for the full IEPOX-SOA particulate mixture have not been reported. Here, we exposed freshly generated IEPOX-SOA particles to heterogeneous oxidation by•OH under humid conditions (relative humidity ∼57%) for 0–15 atmospheric-equivalent days of aging and derived an effective heterogeneous•OH rate coefficient (kOH) of 2.64 ± 0.4 × 10–13cm3molecules–1s–1. While ∼44% of particulate organic mass of nonoxidized IEPOX-SOA was consumed over the entire 15 day aging period, only <7% was consumed during the initial 10 aging days. By molecular-level chemical analysis, we determined oligomers were consumed at a faster rate (by a factor of 2–4) than monomers. Analysis of aerosol physicochemical properties shows that IEPOX-SOA has a core–shell morphology, and the shell becomes thinner with•OH oxidation. In summary, this study demonstrates that heterogeneous•OH oxidation of IEPOX-SOA particles is a dynamic process in which aerosol chemical composition and physicochemical properties play important roles.