棕碳（BrC）是有机气溶胶的重要组成，因其明显的吸光效应而对全球辐射平衡有重要影响。由于对其来源（尤其是二次来源）和大气演化认识不足，准确预测BrC对大气气溶胶全球辐射强迫的贡献仍是当前气溶胶化学领域研究的难点。越来越多的研究表明云滴中的无机硝酸盐在光照作用下可以产生羟基自由基和硝化剂，进而影响BrC的生成。而真实生物质燃烧产生的不同芳香化合物之间的相互作用会使液相反应变得更加复杂。近年来，我国城市群颗粒态无机硝酸盐浓度不断增加，然而硝酸盐在液相反应中对BrC的生成和理化性质改变的影响仍不明确。本项目拟结合液相反应器和最新的高分辨质谱技术，研究无机硝酸盐对生物质燃烧标志物和真实生物质燃烧样品液相反应生成BrC的影响，详细阐明无机硝酸盐对BrC生成量、组成、吸光性质和反应机制的影响。项目成果将为BrC的模型预测和相关空气污染控制提供科学数据和基础依据。

Brown carbon (BrC) constitutes a substantial fraction of organic matter and significantly impacts global radiative balance due to its large optical absorbing properties. However, it remains difficult to accurately estimate the global radiative forcing caused by BrC due to its unclear sources (especially secondary sources) and its unknown aging processes. Increasing evidence also shows that inorganic nitrate in cloud droplets can contribute to the formation of BrC by producing hydroxyl radicals and nitrating agents under illumination. Interactions between different aromatic compounds will further complicate the reaction processes in the real biomass burning smoke. In recent years, particle phase inorganic nitrate concentration has increased continuously in megacities of China. However, our knowledge of the effects of nitrate on the formation and the physiochemical properties of SOA via aqueous-phase processing is still very limited. We propose to investigate the role of inorganic nitrate in the formation of BrC from biomass burning related aromatic compounds, as well as real biomass burning aerosols sampled from fields, using an aqueous reactor and the state-of-the-art high-resolution mass spectrometry. The influence of inorganic nitrate on the production, composition, optical properties and formation mechanisms of BrC will be elucidated. The results will provide scientific data and valuable information for the prediction of SOA and the mitigation of air pollution.