碳来源与大气过程对碳质气溶胶分子组成和光吸收特性的影响

Organic aerosol is one of the most important components of atmospheric aerosols. In recent years, organic aerosol, not including black carbon, has been found and proved to be light absorbing in UV-Visible region. Light absorbing organic carbon (also named as brown carbon) sources and composition are complex, and its light absorption contributions to radiative forcing, regional air quality, and global climate change have drawn much attention. With the impact of climate change, the BrC has been one of the forefronts in the field of atmospheric research. However, up to now, basic researches on light absorbing organic carbon are still limited in China. Proportioning the BrC sources can accurately estimate the relative contribution of climatic effects of atmospheric aerosols and is the scientific basis for rational pollution reduction policy. Radiocarbon analysis is a powerful tool, which allows to quantitatively apportion between combustion and non-combustion products derived from fossil fuels (14C free or “dead”) and those formed from modern biomass (contemporary levels of 14C; “alive”). In this project, PM2.5 in the Pearl River Delta will be collected by the active sampler, and samples will be analyzed for Brown Carbon. The aims of the project is (1) to character the spatial and seasonal variation of the light absorption of BrC across the PRD; (2) to reveal the relationship between the chemical composition and optical absorption properties of BrC based on High resolution mass spectrometry (FT-ICR); (3) to find out the effects of carbon source and atmospheric processing on the chemical composition and optical absorption properties of BrC based on carbon isotopes (14C and 13C) and biomarkers; (4) clarify the potential controlling factors on the spatial and seasonal variation of optical absorption properties of BrC. Finally, the results of this project will be a scientific basis and theoretical support for the development of air pollution control countermeasures.

有机气溶胶(CA)是大气PM2.5中的重要组份。近年发现,CA中非黑碳类组份具有在紫外-近可见光波段较强的光吸收能力,此类吸光CA(即棕色碳BrC)来源广泛,组成复杂,对人体健康、大气能见度和辐射强迫有着重要的影响。随着气候变化的影响加剧,BrC成为目前大气领域的研究热点与重点之一。然而,BrC的基础研究较为薄弱,特别是其组成及来源的认识仍十分有限。识别BrC的来源是准确估算气溶胶的气候效应、制定合理的污染减排措施的科学基础。碳同位素（14C和13C）是判别CA来源的有效手段。本研究拟以珠三角BrC为研究对象，获得珠三角BrC吸光特性的时空分布特征，基于FT-ICR高分辨质谱技术和碳同位素示踪作用，揭示BrC分子组成影响其光吸收特征的内在机理，查明碳源与大气过程如何决定有机碳分子组成与光学特性，厘清BrC光吸收特征时空变化的影响因素和控制因子，为制定大气污染防治对策提供科学依据和理论支持。

有机气溶胶(CA)是大气PM2.5中的重要组份。近年发现，CA中非黑碳类组份具有在紫外-近可见光波段较强的光吸收能力,此类吸光CA（即棕色碳BrC）来源广泛,组成复杂,对人体健康、大气能见度和辐射强迫有着重要的影响。随着气候变化的影响加剧，BrC成为目前大气领域的研究热点与重点之一。然而，BrC的基础研究较为薄弱，特别是其组成及来源的认识仍十分有限。识别BrC的来源是准确估算气溶胶的气候效应、制定合理的污染减排措施的科学基础。本项目结合多种方法和手段，对典型棕色碳排放源的分子组成做了高分辨质谱特征的定性和定量研究；对棕色碳在气溶胶中的存在形态、分子组成、吸光特性和来源开展了系统研究；利用机器学习技术揭示了大气环境中棕色碳分子组成与吸光特性变化的影响因素；并利用同位素示踪技术，定量解析了广州市大气棕色碳的来源。研究结果显示，生物质燃烧产生的气溶胶中吸光能力要高于燃煤和机动车尾气排放；珠三角大气中主要吸光物质为HULIS，其次为弱极性组分，各组分吸光能力受生物质燃烧贡献大小的影响；大数据分析显示，主要吸光分子以含氮的苯系物和稠环芳烃物质为主，其吸光增强主要受生物质燃烧和二次硝化反应产物的影响；大气中OH自由基是导致棕色碳吸光能力降低的最主要环境因子；210Pb和7Be的结果显示，近地面的区域外源性输入是导致广州市大气棕色碳秋冬季增强的主要原因，外源输入约占总吸光50%，主要来源为生物质燃烧和二次硝化反应产物，其中生物质燃烧占外源性输入总吸光值的三分之二。本项目所获结果揭示了BrC分子组成影响其光吸收特征的内在机理，查明了碳源与大气过程如何决定有机碳分子组成与光学特性，厘清了BrC光吸收特征时空变化的影响因素和控制因子，为科学认识大气棕色碳和制定大气污染防治对策提供了重要的科学依据和理论支持。 依托本项目，共发表论文16篇，其中SCI论文14篇，中文核心期刊2篇。培养博士研究生2名（莫扬之和姜鸿兴）。