Abstract：
The pollution burdens and compositions of atmospheric brown carbon (BrC) that determine their impacts on climate-health-ecosystems have not been well studied, particularly in some mega-economic coastal areas. Herein, atmospheric BrC samples synchronously collected from urban Shanghai (SH) and Huaniao Island (HNI) in the East China Sea during winter were characterized through ultrahigh-performance liquid chromatography-diode array detector-high resolution mass spectrometry (UHPLC-DAD-HRMS). The three polarity-dependent BrC fractions exhibited significant differences in both light absorption and chromophore composition. The average light absorption coefficients of BrC subfractions at 365 nm in SH were 2.6-3.7 times higher than those in HNI. The water-insoluble BrC (WIS-BrC) and humic-likes BrC (HULIS-BrC) dominated the total BrC absorption in SH (45 ± 7 %) and HNI (43 ± 6 %), respectively. Compared with SH, the higher O/Cw, lower molecule conjugation degree, and reduced mass absorption efficiency at 365 nm (MAE365) in HNI imply a potential bleaching mechanism during the transportation oxidation process. Thousands of BrC chromophores were detected at both sites. >20 major chromophores with strong absorption were unambiguously identified in HULIS-BrC and accounted for ∼40 % of the HULIS light absorption at 365 nm at both sites. These chromophores in SH HULIS-BrC featured oxygenated aromatics and nitroaromatics, while alkyl benzenesulfonic acids with emissions from cargo ships were found in HNI HULIS-BrC. Moreover, 22 major chromophores identified in WIS-BrC included alkaloids, polyaromatic hydrocarbons (PAHs), and carbonyl oxygenated PAHs, contributing 39 % and 49 % of the WIS-BrC light absorption at 365 nm in SH and HNI, respectively. Ascertaining the molecular-specific optical properties of BrC chromophores over the mega-economic coastal area is helpful for the predictive understanding of the sources and evolution of BrC, as well as its atmospheric behavior from land to sea.
摘要：
大气褐碳（BrC）的污染负担和成分决定了它们对气候健康生态系统的影响尚未得到很好的研究。特别是在一些大型经济沿海地区。在这里，通过超高效液相色谱-二极管阵列检测器-高分辨率质谱（UHPLC-DAD-HRMS）对冬季从东海城市（SH）和华庙岛（HNI）同步采集的大气BrC样品进行了表征。三种极性依赖性BrC级分在光吸收和发色团组成方面均表现出显着差异。SH中BrC亚组分在365nm处的平均光吸收系数是HNI中的2.6-3.7倍。水不溶性BrC（WIS-BrC）和类腐殖质BrC（HULIS-BrC）主导了SH（45±7％）和HNI（43±6％）的总BrC吸收，分别。与SH相比,O/Cw越高，较低的分子共轭程度，在HNI中，在365nm（MAE365）处的质量吸收效率降低暗示了运输氧化过程中潜在的漂白机制。在两个位点检测到数千个BrC发色团。在HULIS-BrC中明确鉴定出>20种具有强吸收的主要发色团,并且在两个位点在365nm处占HULIS光吸收的约40%。SHHULIS-BrC中的这些发色团以含氧芳烃和硝基芳烃为特征，而在HNIHULIS-BrC中发现了从货船排放的烷基苯磺酸。此外，在WIS-BrC中鉴定的22种主要发色团包括生物碱，多环芳烃(PAHs)，和羰基氧化的PAHs，在SH和HNI中，在365nm处贡献了39％和49％的WIS-BrC光吸收，分别。确定大型经济沿海地区BrC发色团的分子特异性光学特性有助于对BrC的来源和演化的预测性理解，以及它从陆地到海洋的大气行为。
