Organic aerosols (OAs) have important influences on the climatic implications and health effects of atmospheric aerosols. Among the complex OA constituents, brown carbon (BrC) accounts for a substantial mass fraction and is of special interest because of its light‐absorbing properties. In this study, the chemical composition of atmospheric OAs over the middle‐lower Yangtze River (MLYR) channel, as well as the BrC, was investigated during a ship cruise campaign in winter 2015. In total, more than 1,000 molecular formulas were determined using a combination of ultra‐high performance liquid chromatography (UHPLC), a diode array detector (DAD), and Orbitrap high‐resolution mass spectrometry (HRMS). Large numbers and enhanced signal abundances for known tracers as well as monocyclic and polycyclic aromatics indicate that biomass burning and fossil combustion are important sources of OAs over the MLYR channel. In addition, 13 chromophores with strong light absorption, mostly representing established biomass burning tracers, were unambiguously determined by UHPLC/DAD/HRMS and contributed to 35–37% of the total light absorption of OAs at 290 nm and 58–70% at 350 nm. Sixty‐three previously identified biomass burning chromophores were also positively identified in the mass spectrometric analysis here but embedded in the humped signal during the spectroscopic analysis. These BrC chromophores exhibit high degrees of unsaturation, suggesting that these compounds are aromatic, nitro‐aromatic, and polycyclic aromatic type of species. Our results highlight the significant influence of biomass burning and fossil combustion on atmospheric OAs over the MLYR channel in the winter, strongly enhancing light‐absorbing properties and decreasing air quality.

中文翻译：

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长江航道上大气有机气溶胶的化学特征和棕碳发色团

有机气溶胶（OAs）对大气气溶胶的气候影响和健康影响具有重要影响。在复杂的OA成分中，棕碳（BrC）占了很大的质量比，并且由于其吸光特性而引起了人们的特别关注。在本研究中，在2015年冬季的游轮活动中研究了长江中下游（MLYR）通道和BrC上的大气OAs的化学组成。使用以下方法确定了1000多个分子式超高效液相色谱（UHPLC），二极管阵列检测器（DAD）和Orbitrap高分辨率质谱（HRMS）的组合。已知示踪剂以及单环和多环芳烃的大量存在和增强的信号丰度表明，生物质燃烧和化石燃烧是MLYR通道上OA的重要来源。此外，UHPLC / DAD / HRMS明确测定了13个具有强光吸收能力的发色团，主要代表已建立的生物质燃烧示踪剂，它们占OAs在290 nm的总光吸收率的35–37％和在350 nm的总发光率的58–70％纳米 在这里的质谱分析中也可以肯定地识别出63个先前识别的生物质燃烧发色团，但在光谱分析过程中嵌入了峰信号中。这些BrC发色团表现出高度的不饱和度，表明这些化合物是芳香族，硝基芳香族和多环芳香族类型的物种。