Thornton Joel A, Mohr Claudia, Schobesberger Siegfried, D'Ambro Emma L, Lee Ben H, Lopez-Hilfiker Felipe D
Department of Atmospheric Sciences, University of Washington, 408 ATG Building, 3920 Okanogan Lane NE, Seattle, Washington 98195, United States.
Department of Environmental Science, Stockholm University, Svante Arrhenius Väg 8, Stockholm 10691, Sweden.
Acc Chem Res. 2020 Aug 18;53(8):1415-1426. doi: 10.1021/acs.accounts.0c00259. Epub 2020 Jul 10.
ConspectusThe complex array of sources and transformations of organic carbonaceous material that comprises an important fraction of atmospheric fine particle mass, known as organic aerosol, has presented a long running challenge for accurate predictions of its abundance, distribution, and sensitivity to anthropogenic activities. Uncertainties about changes in atmospheric aerosol particle sources and abundance over time translate to uncertainties in their impact on Earth's climate and their response to changes in air quality policy. One limitation in our understanding of organic aerosol has been a lack of comprehensive measurements of its molecular composition and volatility, which can elucidate sources and processes affecting its abundance. Herein we describe advances in the development and application of the Filter Inlet for Gases and Aerosols (FIGAERO) coupled to field-deployable High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometers (HRToF-CIMS). The FIGAERO HRToFCIMS combination broadly probes gas and particulate OA molecular composition by using programmed thermal desorption of particles collected on a Teflon filter with subsequent detection and speciation of desorbed vapors using inherently quantitative selected-ion chemical ionization. The thermal desorption provides a means to obtain quantitative insights into the volatility of particle components and thus the physicochemical nature of the organic material that will govern its evolution in the atmosphere.In this Account, we discuss the design and operation of the FIGAERO, when coupled to the HRToF-CIMS, for quantitative characterization of the molecular-level composition and effective volatility of organic aerosol in the laboratory and field. We provide example insights gleaned from its deployment, which improve our understanding of organic aerosol sources and evolution. Specifically, we connect thermal desorption profiles to the effective equilibrium saturation vapor concentration and enthalpy of vaporization of detected components. We also show how application of the FIGAERO HRToF-CIMS to environmental simulation chamber experiments and the field provide new insights and constraints on the chemical mechanisms governing secondary organic aerosol formation and dynamic evolution. We discuss the associated challenges of thermal decomposition during desorption and calibration of both the volatility axis and signal. We also illustrate how the FIGAERO HRToF-CIMS can provide additional insights into organic aerosol through isothermal evaporation experiments as well as for detection of ultrafine particulate composition. We conclude with a description of future opportunities and needs for its ability to further organic aerosol science.
综述
构成大气细颗粒物质量重要组成部分的有机碳质材料来源复杂且经历多种转化，这种材料被称为有机气溶胶，长期以来一直是准确预测其丰度、分布以及对人为活动敏感性的一大挑战。大气气溶胶颗粒来源和丰度随时间变化的不确定性，转化为它们对地球气候影响以及对空气质量政策变化响应的不确定性。我们对有机气溶胶理解的一个局限在于缺乏对其分子组成和挥发性的全面测量，而这些测量能够阐明影响其丰度的来源和过程。在此，我们描述与可实地部署的高分辨率飞行时间化学电离质谱仪（HRToF - CIMS）联用的气体和气溶胶过滤入口（FIGAERO）在研发和应用方面取得的进展。FIGAERO与HRToF - CIMS的组合通过对聚四氟乙烯滤膜上收集的颗粒进行程序升温热脱附，随后使用本质上可定量的选择离子化学电离对脱附蒸汽进行检测和分类，从而广泛探测气体和气态有机气溶胶的分子组成。热脱附提供了一种手段，可对颗粒成分的挥发性以及将决定其在大气中演化的有机材料的物理化学性质获得定量认识。
在本综述中，我们讨论当FIGAERO与HRToF - CIMS联用时的设计与操作，用于在实验室和实地对有机气溶胶的分子水平组成和有效挥发性进行定量表征。我们提供了从其部署中获得的示例见解，这些见解增进了我们对有机气溶胶来源和演化的理解。具体而言，我们将热脱附曲线与检测到的成分的有效平衡饱和蒸汽浓度和汽化焓联系起来。我们还展示了FIGAERO - HRToF - CIMS在环境模拟舱实验和实地的应用如何为控制二次有机气溶胶形成和动态演化的化学机制提供新的见解和限制。我们讨论了脱附过程中热分解以及挥发性轴和信号校准相关的挑战。我们还说明了FIGAERO - HRToF - CIMS如何通过等温蒸发实验以及对超细颗粒组成的检测为有机气溶胶提供更多见解。我们最后描述了其在推动有机气溶胶科学发展方面未来的机遇和需求。
