中国长三角背景点冬季大气棕碳污染特征及来源解析  

Pollution Characteristics and Sources of Wintertime Atmospheric Brown Carbon at a Background Site of the Yangtze River Delta Region in China

作　　者：赵宇[1] 吴灿 王益倩 陈玉宝 吕少君 汪芳琳 杜伟 刘仕杰[1] 丁志健 王格慧 ZHAO Yu;WU Can;WANG Yi-qian;CHEN Yu-bao;LÜShao-jun;WANG Fang-lin;DU Wei;LIU Shi-jie;DING Zhi-jian;WANG Ge-hui(Key Laboratory of Geographic Information Sciences,Ministry of Education,School of Geographic Sciences,East China Normal University,Shanghai 200241,China;Institute of Eco-Chongming,Shanghai 200062,China)

机构地区：[1]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 [2]崇明生态研究院,上海200062

出　　处：《环境科学》2021年第7期3127-3135,共9页Environmental Science

基　　金：国家自然科学基金项目(41773117);国家重点研发计划项目(2017YFC0212703);华东师范大学幸福之花计划项目。

摘　　要：为探究长三角城市群背景点大气棕碳(brown carbon,Br C)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365nm处的吸光系数(absorption coefficients,Abs365,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p H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(R^(2)=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Br C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%.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 2019were analyzed to determine their chemical compositions and optical properties.The results showed that the light absorption coefficient(Abs365,M) of Br C extracted by methanol at 365 nm was (5.39±3.33) M^(-1)·m^(-1),which was 1.3 times of the water extracted Br C.Both increased significantly with the increase of p H values,suggesting that less acidic conditions can enhance the light absorption ability of Br C.In winter,both Abs365and MAE365(mass absorption efficiency) were higher in the nighttime than in the daytime.Astrong linear correlation observed between Abs365and levoglucosan (R^(2)=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 Br C at 365 nm,respectively.Positive matrix factorization (PMF) analysis further showed that biomass and fossil fuel combustions were the main sources of Br C in Chongming Island in winter,accounting for 56%of the total Br C,followed by secondary formation,accounting for 24%of the total Br C,with road dust contributing only 6%.

关 键 词：棕碳(Br C) 化学组分 硝基芳香族化合物(NACs) 多环芳烃(PAHs) 吸光性质 酸度 

分 类 号：X513[环境科学与工程—环境工程]