Xiao Zhi-Mei, Xu Hong, Cai Zi-Ying, Li Peng, Liu Bin, Yuan Jie, Zheng Nai-Yuan, Tang Miao, Chen Kui, Deng Xiao-Wen
Tianjin Eco-Environmental Monitoring Center, Tianjin 300191, China.
Tianjin Environmental Meteorological Center, Tianjin 300074, China.
Huan Jing Ke Xue. 2020 Sep 8;41(9):3879-3888. doi: 10.13227/j.hjkx.202003109.
High-resolution online monitoring data from January to February in 2020 was used to study the characterization of two heavy pollution episodes in Tianjin in 2020; the heavy pollution episode that lasted from January 16 to 18, 2020 (referred to as episode Ⅰ) and that from February 9 to 10, 2020 (referred to as episode Ⅱ) were analyzed. The results showed that two heavy pollution episodes were influenced by regional transportation in the early stage and local adverse meteorological conditions in the later stage. During these episodes, the average wind speed was low, the average relative humidity was close to 70%, and relative humidity approached the saturated, the boundary layer heights were below 300 m, and the horizontal and vertical diffusion conditions were poor. Compared to episode Ⅰ, the concentration of pollutants decreased during episode Ⅱ, especially for the concentration of NO. During the episode Ⅱ, the concentrations of PM and CO were higher in the north of Tianjin. The chemical component concentrations and their mass ratios to PM changed significantly in both episodes; the concentrations of secondary inorganic ions (NO, SO, and NH), elemental carbon (EC) and Cawere higher in episode Ⅰ, the concentrations of organic carbon (OC) and Cl slightly increased in episode Ⅱ; and the concentrations of Kwere higher in episode Ⅱ. Compared to episode Ⅰ, because of the increase in the combustion sources and significant reductions in the number of vehicles, the mass ratios of SO, OC, and K to PM increased while the mass ratios of NO and EC to PM decreased in episode Ⅱ; the mass ratios of NH and Cl to PM were relatively higher due to the continuity of the industrial production processes; the mass ratios of Ca to PM were lower in two heavy pollution episodes because construction activities were halted. Source apportionment of PM was performed using the positive matrix factorization (PMF) model. In episode Ⅰ, the major sources of PM in Tianjin were secondary sources, industrial and coal combustion, vehicle exhaust, crustal dust, fireworks and biomass burning, with contributions of 53.8%, 20.2%, 18.6%, 6.3%, and 1.1%, respectively. In episode Ⅱ, the same sources were identified in the PMF analysis with contributions of 48.3%, 28.2%, 8.7%, 2.6%, and 12.2%, respectively. Compared to episode Ⅰ, the contributions of industrial and coal combustion, fireworks and biomass burning increased, and the contributions of secondary sources, vehicle exhaust, and crustal dust decreased in episode Ⅱ; contributions of vehicle exhaust and crustal dust decreased by 53.2% and 58.7%, respectively.
利用2020年1月至2月的高分辨率在线监测数据，研究了2020年天津市两次重污染过程的特征；分析了2020年1月16日至18日持续的重污染过程（简称过程Ⅰ）和2月9日至10日持续的重污染过程（简称过程Ⅱ）。结果表明，两次重污染过程前期受区域传输影响，后期受本地不利气象条件影响。在这些过程中，平均风速较低，平均相对湿度接近70%，相对湿度接近饱和，边界层高度低于300米，水平和垂直扩散条件较差。与过程Ⅰ相比，过程Ⅱ中污染物浓度下降，尤其是NO浓度。在过程Ⅱ中，天津市北部的PM和CO浓度较高。两次过程中化学成分浓度及其与PM的质量比均发生了显著变化；过程Ⅰ中二次无机离子（NO、SO和NH）、元素碳（EC）和Ca的浓度较高，过程Ⅱ中有机碳（OC）和Cl的浓度略有增加；过程Ⅱ中K的浓度较高。与过程Ⅰ相比，由于燃烧源增加和车辆数量显著减少，过程Ⅱ中SO、OC和K与PM的质量比增加，而NO和EC与PM的质量比下降；由于工业生产过程的连续性，NH和Cl与PM的质量比相对较高；由于施工活动停止，两次重污染过程中Ca与PM的质量比均较低。利用正定矩阵因子分解（PMF）模型对PM进行了源解析。在过程Ⅰ中，天津市PM的主要来源是二次源、工业和煤炭燃烧、汽车尾气、地壳扬尘、烟花爆竹和生物质燃烧，贡献率分别为53.8%、20.2%、18.6%、6.3%和1.1%。在过程Ⅱ中，PMF分析识别出相同的来源，贡献率分别为48.3%、28.2%、8.7%、2.6%和12.2%。与过程Ⅰ相比，过程Ⅱ中工业和煤炭燃烧、烟花爆竹和生物质燃烧的贡献率增加，二次源、汽车尾气和地壳扬尘的贡献率下降；汽车尾气和地壳扬尘的贡献率分别下降了53.2%和58.7%。
