中文关键词天津重污染PM_2.5消光系数来源解析 英文关键词Tianjinheavy pollutionPM_2.5extinction coefficientsource apportionment

作者	单位	E-mail
李立伟	天津市生态环境监测中心, 天津 300191	llwabc2010@163.com
肖致美	天津市生态环境监测中心, 天津 300191
杨宁	天津市生态环境监测中心, 天津 300191
蔡子颖	天津市环境气象中心, 天津 300074
闫斌峰	天津市河东区生态环境监测中心, 天津 300170
元洁	天津市生态环境监测中心, 天津 300191
白宇	天津市生态环境监测中心, 天津 300191
郑乃源	天津市生态环境监测中心, 天津 300191
唐邈	天津市生态环境监测中心, 天津 300191	tangmiao32@163.com

中文摘要 为了解天津市2020年冬季重污染过程气溶胶消光特征，基于2020年1~2月高时间分辨率的在线监测数据，对1月16~18日（重污染过程Ⅰ）、1月26~28日（重污染过程Ⅱ）和2月9~10日（重污染过程Ⅲ）进行气溶胶消光特性及其来源分析.结果表明，3次重污染过程PM_2.5平均浓度分别为（229±52）、（219±48）和（161±25）μg·m^-3，NO₃^-、SO₄^2-、NH₄⁺、OC、EC、Cl^-和K⁺为PM_2.5中主要组分.3次重污染过程气溶胶散射系数（Bsp₅₅₀）和吸收系数（Bap₅₅₀）分别为（1055.65±250.17）、（1054.26±263.22）、（704.44±109.89） Mm^-1和（52.96±13.15）、（39.72±8.21）、（34.50±8.53） Mm^-1，散射效应高于吸收效应.重污染天气下硝酸盐（38.9%~48.8%）、硫酸盐（31.1%~40.7%）和OM （9.9%~21.8%）为PM_2.5中最主要消光成分.3次重污染过程PM_2.5组分对气溶胶消光的贡献发生明显变化，重污染过程Ⅰ，硝酸盐对消光系数的贡献最高；重污染过程Ⅱ，受春节期间烟花爆竹燃放影响，OM对消光系数的贡献升高；重污染过程Ⅲ，交通出行减少但燃煤源排放相对稳定，硝酸盐对消光系数的贡献降低，硫酸盐的贡献升高.来源解析结果显示，重污染天气气溶胶消光的主要来源为二次无机气溶胶（37.1%~42.0%）、燃煤和工业（22.9%~24.2%）、机动车（23.9%~27.2%）、扬尘源（5.0%~6.4%）和烟花爆竹及生物质燃烧排放（3.9%~6.2%）.与重污染过程Ⅰ相比，重污染过程Ⅱ烟花爆竹及生物质燃烧排放对消光系数的贡献升高；重污染过程Ⅲ机动车对消光系数的贡献明显降低；燃煤和工业对消光系数的贡献在3次重污染过程中较接近.后轨迹分析表明，重污染天气期间天津市主要以来自河北的小尺度、短距离以及内蒙古中部的中尺度、中短距离气团传输轨迹为主. 英文摘要 This study examined high-resolution online monitoring data from January to February 2020 to study the extinction characteristics and sources of heavy pollution episodes during winter in Tianjin. Heavy pollution episodes occurred during this period from January 16 to 18 (episode Ⅰ), from January 24 to 26 (episode Ⅱ), and from February 9 to 10 (episode Ⅲ). The results showed that the concentrations of PM_2.5 during the three heavy pollution episodes were (229±52), (219±48), and (161±25) μg·m^-3, respectively, with NO₃^-, SO₄^2-, NH₄⁺, OC, EC, Cl^-, and K⁺ comprising the main species. The values of the scattering coefficient(Bsp₅₅₀) during the three heavy pollution episodes were (1055.65±250.17), (1054.26±263.22), and (704.44±109.89) Mm^-1, respectively, while the absorption coefficient(Bap₅₅₀) showed much lower values of (52.96±13.15), (39.72±8.21), and (34.50±8.53) Mm^-1, respectively. PM_2.5 played a major role in atmospheric extinction during heavy pollution episodes. Specifically, nitrate (38.9%-48.8%), sulfate (31.1%-40.7%), and OM (9.9%-21.8%) were the most important extinction components. The contribution of PM_2.5 chemical components to the extinction coefficient varied significantly between the three episodes; the percentage of nitrate was higher in episode Ⅰ than in the other two episodes; in episode Ⅱ, the percentage of OM was highest, significantly affected by the discharge of fireworks; in episode Ⅲ, as traffic decreased but coal combustion emissions remained constant, the contribution of nitrate to the extinction coefficient decreased, while that of sulfate increased. Source apportionment of extinction coefficients was performed using PMF model combined with IMPROVE. Various pollution sources contributed to the extinction coefficient, namely: secondary sources (37.1%-42.0%), industrial and coal combustion (22.9%-24.2%), vehicle exhaust (23.9%-27.2%), crustal dust (5.0%-6.4%), and fireworks and biomass burning (3.9%-6.2%). Compared with episode Ⅰ, the contribution of fireworks and biomass burning increased significantly during episode Ⅱ, while the contribution of vehicle exhaust decreased significantly during episode Ⅲ. The contribution of industrial and coal combustion was similar during all three heavy pollution episodes. According to backward analysis, the small-scale and short-distance transmissions from Hebei provinces, as well as the medium and short-distance transmissions from central Inner Mongolia, were the major sources during heavy pollution episodes in the winter in Tianjin City.

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