Formation and evolution of molecular products in α-pinene secondary organic aerosol
Formation and evolution of molecular products in α-pinene secondary organic aerosol
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DOI：
10.1073/pnas.1517742112
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发表时间：
2015-11
期刊：
影响因子：
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通讯作者：
Xuan Zhang;Renee McVay;D. Huang;N. Dalleska;B. Aumont;R. Flagan;J. Seinfeld
中科院分区：
文献类型：
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作者：
Xuan Zhang;Renee McVay;D. Huang;N. Dalleska;B. Aumont;R. Flagan;J. Seinfeld
二次有机气溶胶（SOA）在气候和空气质量中起着关键作用。几十年来，SOA的分子组成特征一直是一个主要的研究目标，但大多数人为和生物SOA系统的化学动力学仍然没有得到很好的解决。我们在这里报告的SOA的时间分辨分子特征来自典型的α-蒎烯系统，在对流层中最丰富的生物排放之一。我们揭示了SOA组件的分子结构，丰度，生长速率，演化模式，以及对温度，相对湿度和氧化剂类型变化的响应方面的独特功能。我们的研究结果提供了一个全面的分析过程中，管理α-蒎烯SOA的形成和老化。我们对挥发性有机化合物形成大气二次有机气溶胶（SOA）的认识大多来自实验室室测量，包括质量产率和元素组成。仅这些测量不足以确定SOA产生的化学机制。我们在这里提出了一个全面的数据集的分子身份，丰度和动力学的α-蒎烯SOA，一个典型的系统，已受到广泛关注，由于其重要性，作为一个有机气溶胶源在原始大气中。已鉴定的有机物质占α-蒎烯SOA质量的10.58 -72%，其特征在于半挥发性/低挥发性单体和极低挥发性二聚体，它们表现出相当的氧化态，但具有不同的官能度。据我们所知，首次从单个颗粒相组分的动力学揭示了α-蒎烯SOA形成过程的特征。虽然单体产品占主导地位的整体气溶胶质量，二聚体的快速生产起着关键作用，在启动颗粒的增长。在母体α-蒎烯被消耗后，观察到单体的连续生产，这不能仅用气相光化学生产来解释。此外，观察到单体和二聚体对臭氧氧化α-蒎烯与羟基自由基、温度和相对湿度的不同反应。气相自由基结合反应以及不稳定分子的凝聚相重排反应可能解释了新表征的SOA特征，从而为理解α-蒎烯SOA的形成和演化机制开辟了进一步的途径。
Significance Secondary organic aerosol (SOA) plays a pivotal role in climate and air quality. Characterizing the molecular makeup of SOA has been a major research goal for several decades, yet the chemical dynamics of most anthropogenic and biogenic SOA systems remain poorly resolved. We report here the time-resolved molecular characterization of SOA derived from the canonical α-pinene system, one of the most abundant biogenic emissions in the troposphere. We reveal distinct features of SOA components in terms of molecular structure, abundance, growth rates, evolution patterns, and responses to variations in temperature, relative humidity, and oxidant type. Our findings provide a comprehensive analysis of processes governing α-pinene SOA formation and aging. Much of our understanding of atmospheric secondary organic aerosol (SOA) formation from volatile organic compounds derives from laboratory chamber measurements, including mass yield and elemental composition. These measurements alone are insufficient to identify the chemical mechanisms of SOA production. We present here a comprehensive dataset on the molecular identity, abundance, and kinetics of α-pinene SOA, a canonical system that has received much attention owing to its importance as an organic aerosol source in the pristine atmosphere. Identified organic species account for ∼58–72% of the α-pinene SOA mass, and are characterized as semivolatile/low-volatility monomers and extremely low volatility dimers, which exhibit comparable oxidation states yet different functionalities. Features of the α-pinene SOA formation process are revealed for the first time, to our knowledge, from the dynamics of individual particle-phase components. Although monomeric products dominate the overall aerosol mass, rapid production of dimers plays a key role in initiating particle growth. Continuous production of monomers is observed after the parent α-pinene is consumed, which cannot be explained solely by gas-phase photochemical production. Additionally, distinct responses of monomers and dimers to α-pinene oxidation by ozone vs. hydroxyl radicals, temperature, and relative humidity are observed. Gas-phase radical combination reactions together with condensed phase rearrangement of labile molecules potentially explain the newly characterized SOA features, thereby opening up further avenues for understanding formation and evolution mechanisms of α-pinene SOA.