中文关键词天津重污染PM_2.5污染特征来源解析 英文关键词Tianjinheavy pollutionPM_2.5pollution characterizationsource apportionment

作者	单位	E-mail
肖致美	天津市生态环境监测中心, 天津 300191	xiaozhimei01@163.com
徐虹	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
李鹏	天津市生态环境监测中心, 天津 300191
刘彬	天津市生态环境监测中心, 天津 300191
元洁	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
陈魁	天津市生态环境监测中心, 天津 300191	kuichen@126.com
邓小文	天津市生态环境监测中心, 天津 300191	dxwpp@163.com

中文摘要 为了解2020年天津市两次重污染天气污染特征，基于2020年1~2月高时间分辨率的在线监测数据，对天津市2020年1月16~18日（重污染过程Ⅰ）和2020年2月9~10日（重污染过程Ⅱ）进行分析，结果表明，两次重污染过程均呈现前期区域输送和后期本地不利气象条件叠加双重影响的特点，重污染过程期间平均风速均较低，平均相对湿度接近70%，部分时段接近饱和，边界层高度低于300 m，水平和垂直扩散条件均较差.与重污染过程Ⅰ相比，重污染过程Ⅱ主要污染物浓度和污染程度均降低，尤其是NO₂浓度下降明显，重污染过程Ⅱ北部地区PM_2.5和CO浓度较高.两次重污染过程PM_2.5中化学组分浓度和占比发生明显变化，重污染过程Ⅰ二次无机离子（SO₄^2-、NO₃^-和NH₄⁺）、EC和Ca²⁺平均浓度较高，OC和Cl^-平均浓度略低于重污染过程Ⅱ，K⁺平均浓度低于重污染过程Ⅱ.与重污染过程Ⅰ相比，受燃烧源增加和移动源大幅降低影响，重污染过程Ⅱ中SO₄^2-、OC和K⁺在PM_2.5中占比明显上升，NO₃^-和EC在PM_2.5中占比明显下降；工业持续生产使重污染Ⅱ中NH₄⁺和Cl^-在PM_2.5中占比相对较高；工地的停工使两次重污染过程中Ca²⁺占比均较低.PMF解析结果表明，重污染过程Ⅰ中PM_2.5来源为二次离子、燃煤和工业、机动车、扬尘、烟花爆竹及生物质燃烧，贡献率分别为53.8%、20.2%、18.6%、6.3%和1.1%；重污染过程Ⅱ中各源对PM_2.5的贡献率分别为48.3%、28.2%、8.7%、2.6%和12.2%.与重污染过程Ⅰ相比，重污染过程Ⅱ燃煤和工业、烟花爆竹及生物质燃烧对PM_2.5贡献率明显上升，二次离子、机动车和扬尘贡献率明显下降，尤其是机动车和扬尘，贡献率分别下降53.2%和58.7%. 英文摘要 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 NO₂. During the episode Ⅱ, the concentrations of PM_2.5 and CO were higher in the north of Tianjin. The chemical component concentrations and their mass ratios to PM_2.5 changed significantly in both episodes; the concentrations of secondary inorganic ions (NO₃^-, SO₄^2-, and NH₄⁺), elemental carbon (EC) and Ca²⁺were higher in episode Ⅰ, the concentrations of organic carbon (OC) and Cl^- slightly increased in episode Ⅱ; and the concentrations of K⁺were 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 SO₄^2-, OC, and K⁺ to PM_2.5 increased while the mass ratios of NO₃^- and EC to PM_2.5 decreased in episode Ⅱ; the mass ratios of NH₄⁺ and Cl^- to PM_2.5 were relatively higher due to the continuity of the industrial production processes; the mass ratios of Ca²⁺ to PM_2.5 were lower in two heavy pollution episodes because construction activities were halted. Source apportionment of PM_2.5 was performed using the positive matrix factorization (PMF) model. In episode Ⅰ, the major sources of PM_2.5 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.

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