Air Pollution Research Center, University of California, Riverside, Riverside, CA 92521, USA.
Chem Soc Rev. 2012 Oct 7;41(19):6582-605. doi: 10.1039/c2cs35122f. Epub 2012 Aug 31.
Secondary organic aerosol (SOA) is formed in the atmosphere when volatile organic compounds (VOCs) emitted from anthropogenic and biogenic sources are oxidized by reactions with OH radicals, O(3), NO(3) radicals, or Cl atoms to form less volatile products that subsequently partition into aerosol particles. Once in particles, these organic compounds can undergo heterogenous/multiphase reactions to form more highly oxidized or oligomeric products. SOA comprises a large fraction of atmospheric aerosol mass and can have significant effects on atmospheric chemistry, visibility, human health, and climate. Previous articles have reviewed the kinetics, products, and mechanisms of atmospheric VOC reactions and the general chemistry and physics involved in SOA formation. In this article we present a detailed review of VOC and heterogeneous/multiphase chemistry as they apply to SOA formation, with a focus on the effects of VOC molecular structure on the kinetics of initial reactions with the major atmospheric oxidants, the subsequent reactions of alkyl, alkyl peroxy, and alkoxy radical intermediates, and the composition of the resulting products. Structural features of reactants and products discussed include compound carbon number; linear, branched, and cyclic configurations; the presence of C[double bond, length as m-dash]C bonds and aromatic rings; and functional groups such as carbonyl, hydroxyl, ester, hydroxperoxy, carboxyl, peroxycarboxyl, nitrate, and peroxynitrate. The intention of this review is to provide atmospheric chemists with sufficient information to understand the dominant pathways by which the major classes of atmospheric VOCs react to form SOA products, and the further reactions of these products in particles. This will allow reasonable predictions to be made, based on molecular structure, about the kinetics, products, and mechanisms of VOC and heterogeneous/multiphase reactions, including the effects of important variables such as VOC, oxidant, and NO(x) concentrations as well as temperature, humidity, and particle acidity. Such knowledge should be useful for interpreting the results of laboratory and field studies and for developing atmospheric chemistry models. A number of recommendations for future research are also presented.
二次有机气溶胶（SOA）是在大气中形成的，当挥发性有机化合物（VOCs）从人为和生物源排放出来时，会与 OH 自由基、O（3）、NO（3）自由基或 Cl 原子发生氧化反应，形成挥发性较低的产物，随后这些产物分配到气溶胶颗粒中。一旦进入颗粒，这些有机化合物就可以进行非均相/多相反应，形成更高氧化或低聚物产物。SOA 构成了大气气溶胶质量的很大一部分，对大气化学、能见度、人类健康和气候都有重大影响。以前的文章已经综述了大气 VOC 反应的动力学、产物和机制，以及 SOA 形成所涉及的一般化学和物理。在本文中，我们详细回顾了 VOC 和非均相/多相化学在 SOA 形成中的应用，重点关注 VOC 分子结构对与主要大气氧化剂初始反应动力学的影响、烷基、过氧烷基和烷氧基自由基中间体随后的反应，以及产物的组成。讨论的反应物和产物的结构特征包括化合物的碳数；线性、支链和环状结构；C[双键，长度为破折号]C 键和芳环的存在；以及羰基、羟基、酯、羟过氧基、羧基、过氧羧酸、硝酸盐和过氧硝酸盐等官能团。本文的目的是为大气化学家提供足够的信息，以了解大气中主要类别的 VOC 反应形成 SOA 产物的主要途径，以及这些产物在颗粒中的进一步反应。这将允许根据分子结构，对 VOC 和非均相/多相反应的动力学、产物和机制，包括 VOC、氧化剂和 NO（x）浓度以及温度、湿度和颗粒酸度等重要变量的影响，做出合理的预测。这种知识对于解释实验室和现场研究的结果以及开发大气化学模型应该是有用的。本文还提出了一些未来研究的建议。
