中文关键词棕碳(BrC)化学组分硝基芳香族化合物(NACs)多环芳烃(PAHs)吸光性质酸度 英文关键词brown carbon (BrC)chemical compositionnitrated aromatic compounds (NACs)polycyclic aromatic hydrocarbons (PAHs)light-absorbing propertyacidity

作者	单位	E-mail
赵宇	华东师范大学地理科学学院, 地理信息科学教育部重点实验室, 上海 200241	zy08221004@163.com
吴灿	华东师范大学地理科学学院, 地理信息科学教育部重点实验室, 上海 200241
王益倩	华东师范大学地理科学学院, 地理信息科学教育部重点实验室, 上海 200241
陈玉宝	华东师范大学地理科学学院, 地理信息科学教育部重点实验室, 上海 200241
吕少君	华东师范大学地理科学学院, 地理信息科学教育部重点实验室, 上海 200241
汪芳琳	华东师范大学地理科学学院, 地理信息科学教育部重点实验室, 上海 200241
杜伟	华东师范大学地理科学学院, 地理信息科学教育部重点实验室, 上海 200241
刘仕杰	华东师范大学地理科学学院, 地理信息科学教育部重点实验室, 上海 200241
丁志健	华东师范大学地理科学学院, 地理信息科学教育部重点实验室, 上海 200241
王格慧	华东师范大学地理科学学院, 地理信息科学教育部重点实验室, 上海 200241 崇明生态研究院, 上海 200062	ghwang@geo.ecnu.edu.cn

中文摘要 为探究长三角城市群背景点大气棕碳（brown carbon，BrC）的污染特征及来源，本研究采集并分析了长三角城市群下风向地区上海崇明岛2018年12月~2019年1月大气PM_2.5样品的化学组成及光学特性.结果表明，甲醇萃取的棕碳在波长365 nm处的吸光系数（absorption coefficients，Abs_365，M）平均为（5.39±3.33）M^-1·m^-1，是水萃取棕碳的1.3倍，且二者均随pH值的增大而显著增加，显示大气颗粒物酸度较弱时有利于棕碳光吸收.冬季Abs₃₆₅和单位质量吸光效率（mass absorption efficiency，MAE₃₆₅）均呈现出夜高昼低的变化趋势，且夜间Abs₃₆₅与左旋葡聚糖呈强线性相关（R²=0.72），说明生物质燃烧排放大量的吸光性物质是导致夜间Abs₃₆₅较高的一个重要原因.冬季硝基芳香族化合物（nitro-aromatic compounds，NACs）和多环芳烃（polycyclic aromatic hydrocarbons，PAHs）平均浓度分别为（1.5±1.1）ng·m^-3和（8.3±4.7）ng·m^-3，作为棕碳重要的发色基团，二者在365 nm波长处对BrC的吸光贡献分别为0.1%和0.067%.正交矩阵源解析（positive matrix factorization，PMF）分析表明，生物质和化石燃料等燃烧源的直接排放是冬季崇明岛棕碳的主要来源，贡献达56%，其次是二次生成棕碳，占比为24%，而道路扬尘源仅占6%. 英文摘要 To investigate the pollution characteristics and sources of atmospheric brown carbon (BrC) in Chongming Island, a background site of the Yangtze River Delta (YRD) region in China, PM_2.5 samples collected from December 2018 to January 2019 were analyzed to determine their chemical compositions and optical properties. The results showed that the light absorption coefficient (Abs_365,M) of BrC extracted by methanol at 365 nm was (5.39±3.33) M^-1·m^-1, which was 1.3 times of the water extracted BrC. Both increased significantly with the increase of pH values, suggesting that less acidic conditions can enhance the light absorption ability of BrC. In winter, both Abs₃₆₅ and MAE₃₆₅ (mass absorption efficiency) were higher in the nighttime than in the daytime. A strong linear correlation observed between Abs₃₆₅ and levoglucosan (R²=0.72) indicated that many light absorbing substances in Chongming Island were derived from biomass burning emissions. During the campaign, nitro-aromatic compounds (NACs) and PAHs accounted for (1.5±1.1) ng·m^-3 and (8.3±4.7) ng·m^-3, respectively, contributing to 0.1% and 0.067% of the absorption of the total BrC at 365 nm, respectively. Positive matrix factorization (PMF) analysis further showed that biomass and fossil fuel combustions were the main sources of BrC in Chongming Island in winter, accounting for 56% of the total BrC, followed by secondary formation, accounting for 24% of the total BrC, with road dust contributing only 6%.

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