大气棕色碳的化学组分与来源解析

The light-absorbing organic aerosol (OA), which is commonly referred to as “brown carbon” (BrC), has become one of the forefronts in the field of atmospheric research due to its significant impacts on photochemical reactions, visibility, and climate change at various geographical scales. However, there is a lack in the standard methods determining brown carbon currently. It is necessary to enhance the inter-comparison between the new solution method and the traditional optical methods, thus to evaluate the accuracy on the analysis of brown carbon optical properties. In addition, our understanding on the chemical composition of brown carbon in the real atmosphere remains limited, which makes it a challenge investigating the relationship between brown carbon sources and light absorption. In this project, we plan to apply both traditional optical methods and the novel solution method in the estimation of brown carbon light absorption, and provide assessments and suggestions on both methods. In addition, by incorporating Mie theory into the BrC determination system, a model on the mixing state of light-absorbing aerosols will be established based on ambient atmospheric conditions. Meanwhile, with the application of multiple mass spectrometry techniques, the chemical composition of brown carbon samples will be analyzed, and further incorporated into source apportionment models. A systematic analysis on the effects and contributions from various sources to BrC light absorbing properties will be performed, which could further provide theoretical and data support for the cooperative control of brown carbon and other emitted pollutants.

大气中的可吸光有机气溶胶，又称棕色碳，因其在不同地域尺度上对光化学过程、能见度、气候变化均有重要影响而成为大气环境研究领域的国际前沿和热点。然而，目前棕色碳的测定尚缺乏统一的标准方法，需要在引入溶液法等新方法的基础上加强与传统光学方法的比照，以确定棕色碳光学性质分析的准确性和可靠性。此外，对真实大气环境中棕色碳化学组成的了解还十分有限，这为探索棕色碳来源对其光学性质的影响增加了难度。本项目拟从传统光学方法和溶液法两个方向出发，对棕色碳的测定方法进行可靠性评估；结合米氏散射理论，建立符合实际情形的可吸光颗粒物混合状态模型；进而在联合运用多种质谱手段细致分析棕色碳化学组成的基础上运用受体模型开展源解析，明确棕色碳各来源对其光吸收特征的影响，为棕色碳和其他污染物的协同控制提供理论依据与数据支持。

近年来，棕色碳，即可吸光有机颗粒物，因其在不同地域尺度上对光化学过程、能见度、气候变化的潜在重要影响而获得了大量关注。本项目立足于东北寒区城市这一典型观测现场，基于其颗粒物浓度高、化学组成和来源复杂的宏观背景，针对棕色碳的理化性质、来源解析和气候效应开展了研究。在实现棕色碳吸收光谱分析平台搭建的基础上，探索并改进了高浓度颗粒物样品理化性质的分析方法，发现甲醇提取方法可以有效抑制热-光学分析过程中从有机碳到焦化碳的转化过程，进而显著提高棕色碳和黑碳质量浓度的测定准确性。对哈尔滨地区棕色碳的季节变化规律进行探讨时，发现生物质燃烧排放是大气棕色碳的重要影响因素，并将哈尔滨地区的生物质燃烧确定为低效率的户外秸秆焚烧。将左旋葡聚糖等生物质燃烧有机示踪物种和棕色碳的理化性质参数共同引入PMF源解析模型，发现生物质燃烧对棕色碳的质量浓度与吸光系数均有重要贡献，且棕色碳污染水平变化主要受秸秆焚烧这一因子的驱动。基于醇提后棕色碳和黑碳结果的计算表明，棕色碳对吸光的相对贡献在紫外波段可高达~275%，在可见光波段也能达到80%以上。可见东北寒区的高强度生物质燃烧排放不仅能导致严重的雾霾污染，还有可能对辐射强迫产生重要影响。

内容获取失败，请点击重试