Chemical Nature and Origins of Atmospheric Brown Carbon Aerosol

棕色碳（BrC）是大气气溶胶中一类特殊的吸光有机物，具有潜在的直接和间接气候效应。据推测，BrC的形成与生物质燃烧羽流或光化学烟雾中有机化合物的氧化和/或齐聚有关，从而产生相对高分子量（MW）、低挥发性的多羧基化合物。该项目旨在更好地了解BrC的化学性质，并解决有关BrC来源的假设。首先，将开发一种独特的分析方法，可以同时进行热/光学表征以及质谱分析（软电离和硬电离），并将其应用于标准和现实世界气溶胶样品的全面收集。该方法将集成内华达州里诺沙漠研究所（DRI）开发的碳分析仪，以及罗斯托克大学（UR）开发的光电离飞行时间质谱仪（TOF-MS），增强了多元素和光谱检测能力。BrC和黑碳（BC）可以通过光谱光吸收测量来量化，并在不同加热温度下形成的气体中使用分子模式/源特征进行研究。研究BrC与各种有机基团的关系。我们将探索一种动态温度梯度，以便更好地分离BrC和其他有机成分，以获得更具体的表征。最后，建立主要气溶胶类型的二维质谱热图库，包括城乡环境颗粒物和实验室产生的燃烧和二次有机气溶胶。当与先进的化学计量分析相结合时，该库将促进源归因。

Brown carbon (BrC) is a special class of light-absorbing organic matter in atmospheric aerosol that has potential direct and indirect climate effects. The formation of BrC is hypothesized to be related to the oxidation and/or oligomerization of organic compounds in biomass burning plumes or photochemical smog leading to relatively high-molecular weight (MW), low-volatility polycarboxylic compounds. This project seeks to better understand the chemical nature of BrC and address hypotheses regarding BrC sources. First, an unique analytical method that allows simultaneous thermal/optical characterization as well as mass spectrometric analysis (soft and hard ionization) of the evolved gases will be developed and applied to a comprehensive collection of standard and real-world aerosol samples. The method will integrate a carbon analyzer developed at the Desert Research Institute (DRI) in Reno,Nevada, enhanced for multi-elemental and spectral detection with photo-ionization time-of-flight mass spectrometers (TOF-MS) developed at the University of Rostock (UR). BrC and black carbon (BC) can then be quantified from spectral light absorption measurements and studied with molecular patterns/source signatures in gases evolved at different heating temperatures. The relationship of BrC to various organic groups will be investigated. A dynamic temperature ramping will be explored to better isolate BrC and other organic components for a more specific characterization. Finally, a library consisting of two-dimensional MS-thermograms for major aerosol types, including urban and rural environmental particulate matter and laboratory-generated combustion and secondary organic aerosol, will be established. This library will facilitate source attribution when coupled with advanced chemometric analysis.