Cai Dongmei, Li Chunlin, Lin Jingxin, Sun Wenwen, Zhang Miaomiao, Wang Tao, Abudumutailifu Munila, Lyu Yan, Huang Xiaojuan, Li Xiang, Chen Jianmin
Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science & Engineering, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, Fudan University, Shanghai 200438, China.
College of Environmental Science and Engineering, Tongji University, Shanghai 200072, China.
Sci Total Environ. 2024 Sep 1;941:173782. doi: 10.1016/j.scitotenv.2024.173782. Epub 2024 Jun 5.
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/C, lower molecule conjugation degree, and reduced mass absorption efficiency at 365 nm (MAE) 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.
大气棕碳（BrC）的污染负担和组成决定了它们对气候、健康和生态系统的影响，但尚未得到充分研究，尤其是在一些经济发达的沿海地区。在此，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）对冬季期间在中国东部上海市区（SH）和东海花鸟岛（HNI）同步采集的大气BrC样本进行了表征。三种极性相关的BrC组分在光吸收和发色团组成方面均表现出显著差异。SH地区BrC亚组分在365nm处的平均光吸收系数比HNI地区高2.6-3.7倍。水不溶性BrC（WIS-BrC）和类腐殖质BrC（HULIS-BrC）分别在SH地区（45±7%）和HNI地区（43±6%）的总BrC吸收中占主导地位。与SH相比，HNI地区较高的O/C、较低的分子共轭度以及365nm处较低的质量吸收效率（MAE）意味着在传输氧化过程中存在潜在的漂白机制。在两个地点都检测到了数千种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，在两个地点均占365nm处HULIS光吸收的约40%。SH地区HULIS-BrC中的这些发色团以氧化芳烃和硝基芳烃为特征，而在HNI地区HULIS-BrC中发现了来自货船排放的烷基苯磺酸。此外，在WIS-BrC中鉴定出的22种主要发色团包括生物碱、多环芳烃（PAHs）和羰基氧化PAHs，分别占SH和HNI地区365nm处WIS-BrC光吸收的39%和49%。确定经济发达沿海地区BrC发色团的分子特异性光学性质有助于预测性地了解BrC的来源和演变及其从陆地到海洋的大气行为。
