Functional Group Composition of Secondary Organic Aerosol Formed from Ozonolysis of α-Pinene Under High VOC and Autoxidation Conditions
Functional Group Composition of Secondary Organic Aerosol Formed from Ozonolysis of α-Pinene Under High VOC and Autoxidation Conditions
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DOI：
10.1021/acsearthspacechem.8b00117
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发表时间：
2018-11-01
影响因子：
3.4
通讯作者：
Ziemann, Paul J.
中科院分区：
文献类型：
--
作者：
Claflin, Megan S.;Krechmer, Jordan E.;Ziemann, Paul J.
二次有机气溶胶（SOA）的形成从α-蒎烯臭氧分解已被广泛研究，最近的重点是高度氧化的多功能化合物（HOMs），已在实验室和现场研究中观察到的贡献。然而，大多数关于SOA和HOM的化学组成的已知信息包括分子式和基于质谱分析的有限的分子结构鉴定。在这里，我们的特点是SOA形成的α-蒎烯臭氧分解使用衍生化分光光度法定量过氧化物，羰基，羧基，酯和羟基。实验进行了一系列的α-蒎烯浓度和相对湿度，包括制度，其中气相HOMs使用NO3-化学电离质谱检测。与高浓度的α-蒎烯进行的实验结果进行了比较，采用主化学机制，包括气体颗粒和气体壁分区的模型的预测。通过RO 2中心点+RO 2中心点、RO 2中心点+HO 2、RO 2中心点异构化和稳定的Criegee中间体+羧酸或水反应形成的气相单体和二聚体产物似乎有助于SOA的形成，但在颗粒中，这些化合物中的醛和酮基团通常通过Baeyer-与氢过氧化物和过氧羧酸的Villiger反应。证据还表明，含有二酰基过氧化物基团的二聚体的水解有助于羧基和酯基的形成，羟基在SOA中的丰度低于预期（因为少量的气相烷氧基自由基异构化或转化为无法检测到的缩醛低聚物），以及小羰基化合物的气体-颗粒分配可能有助于SOA。
The formation of secondary organic aerosol (SOA) from alpha-pinene ozonolysis has been widely studied, with a recent focus on contributions from highly oxidized multifunctional compounds (HOMs) that have been observed in laboratory and field studies. Most of what is known about the chemical composition of SOA and HOMs, however, consists of molecular formulas and limited molecular structure identification based on mass spectrometric analysis. Here, we characterized the SOA formed from alpha-pinene ozonolysis using derivatization-spectrophotometric methods to quantify peroxide, carbonyl, carboxyl, ester, and hydroxyl groups. Experiments were conducted over a range of alpha-pinene concentrations and relative humidities, including regimes in which gas-phase HOMs were detected using NO3- chemical ionization mass spectrometry. Results for experiments conducted with high concentrations of alpha-pinene were also compared with predictions of a model that employed the Master Chemical Mechanism and included gas-particle and gas-wall partitioning. It appears that gas-phase monomer and dimer products formed through RO2 center dot + RO2 center dot, RO2 center dot + HO2, RO2 center dot isomerization, and stabilized Criegee intermediate + carboxylic acid or water reactions contributed to SOA formation, but that in particles the aldehyde and ketone groups in these compounds were often converted to carboxyl and ester groups through Baeyer-Villiger reactions with hydroperoxides and peroxycarboxylic acids. Evidence also indicates that hydrolysis of dimers containing diacyl peroxide groups contributed to the formation of carboxyl and ester groups, that hydroxyl groups were less abundant in SOA than expected (because of minor gas-phase alkoxy radical isomerization or conversion to an undetectable acetal oligomer), and that gas-to-particle partitioning of small carbonyl compounds may have contributed to SOA.