Department of Environmental Toxicology, University of California, Davis, CA 95616, USA.
Anal Bioanal Chem. 2011 Dec;401(10):3045-67. doi: 10.1007/s00216-011-5355-y. Epub 2011 Oct 5.
Organic species are an important but poorly characterized constituent of airborne particulate matter. A quantitative understanding of the organic fraction of particles (organic aerosol, OA) is necessary to reduce some of the largest uncertainties that confound the assessment of the radiative forcing of climate and air quality management policies. In recent years, aerosol mass spectrometry has been increasingly relied upon for highly time-resolved characterization of OA chemistry and for elucidation of aerosol sources and lifecycle processes. Aerodyne aerosol mass spectrometers (AMS) are particularly widely used, because of their ability to quantitatively characterize the size-resolved composition of submicron particles (PM(1)). AMS report the bulk composition and temporal variations of OA in the form of ensemble mass spectra (MS) acquired over short time intervals. Because each MS represents the linear superposition of the spectra of individual components weighed by their concentrations, multivariate factor analysis of the MS matrix has proved effective at retrieving OA factors that offer a quantitative and simplified description of the thousands of individual organic species. The sum of the factors accounts for nearly 100% of the OA mass and each individual factor typically corresponds to a large group of OA constituents with similar chemical composition and temporal behavior that are characteristic of different sources and/or atmospheric processes. The application of this technique in aerosol mass spectrometry has grown rapidly in the last six years. Here we review multivariate factor analysis techniques applied to AMS and other aerosol mass spectrometers, and summarize key findings from field observations. Results that provide valuable information about aerosol sources and, in particular, secondary OA evolution on regional and global scales are highlighted. Advanced methods, for example a-priori constraints on factor mass spectra and the application of factor analysis to combined aerosol and gas phase data are discussed. Integrated analysis of worldwide OA factors is used to present a holistic regional and global description of OA. Finally, different ways in which OA factors can constrain global and regional models are discussed.
有机物种是空气中颗粒物的一个重要但特征描述较差的组成部分。定量了解颗粒的有机部分（有机气溶胶，OA）对于减少一些混淆气候辐射强迫评估和空气质量管理政策的最大不确定性是必要的。近年来，气溶胶质谱仪越来越多地用于高度时间分辨的 OA 化学特性描述以及气溶胶源和生命周期过程的阐明。由于 Aerodyne 气溶胶质谱仪（AMS）能够定量描述亚微米颗粒（PM(1)）的大小分辨组成，因此特别广泛使用。AMS 以在短时间间隔内获得的集合质谱（MS）的形式报告 OA 的总体组成和时间变化。由于每个 MS 代表由其浓度加权的各个组分的光谱的线性叠加，因此对 MS 矩阵进行多元因子分析已被证明可有效地检索 OA 因子，该因子可提供对数千种单个有机物种的定量和简化描述。因子的总和几乎占 OA 质量的 100%，每个单个因子通常对应于大量具有相似化学成分和时间行为的 OA 成分，这些成分是不同来源和/或大气过程的特征。该技术在气溶胶质谱中的应用在过去六年中迅速发展。在这里，我们回顾了应用于 AMS 和其他气溶胶质谱仪的多元因子分析技术，并总结了现场观测的关键发现。突出显示了提供有关气溶胶源，特别是区域和全球范围内二次 OA 演化的有价值信息的结果。讨论了高级方法，例如对因子质量光谱的先验约束以及将因子分析应用于组合气溶胶和气相数据。对全球 OA 因子的综合分析用于呈现 OA 的整体区域和全球描述。最后，讨论了 OA 因子可以约束全球和区域模型的不同方式。
