Key Laboratory of Middle Atmosphere and Global Environment Observation (LAGEO), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
Key Laboratory of Middle Atmosphere and Global Environment Observation (LAGEO), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China.
J Environ Manage. 2021 Jun 15;288:112370. doi: 10.1016/j.jenvman.2021.112370. Epub 2021 Mar 21.
Central North China Plain (NCP) is one of the most important source region of air pollutants over the Beijing-Tianjin-Hebei (BTH) region. The national government has issued abatement measures to improve the air quality in this area from 2017. To examine the effects of control measures, observational analysis on PM characteristics was performed in a city of central NCP during 2017-2019 to investigate the variation in mass concentration, chemical composition, and emission source of PM. Annual PM concentration significantly reduced by 16% from 2017 to 2019, implying substantial improvements in air quality. PM enriched in autumn-winter seasons was dominated by SNA (sum of sulfate, nitrate and ammonium; ~38%), followed by organic carbon matters (OM; ~24%) and fine soil (FS; ~12%). This chemical composition was different from that in a megacity in NCP (Beijing) where OM accounted for a comparable fraction to SNA. Approximately half of SNA was attributed to nitrate, indicating that SNA changed from sulfate-driven to nitrate-driven, and the considerable effects of coal combustion cutoff, in which sulfate was concentrated. Decreased mass fraction of SNA and increased OM fraction in PM were observed in 2018-2019 partly contributed to the decrease in PM. A progressive increase in the contribution of heterogeneous formed SNA whilst a decrease in OM was observed as the pollution elevated from clean to heavily polluted. Six sources (soil dust, biomass burning, secondary emission, road traffic, coal combustion and industry) were identified by the Positive Matrix Factorization (PMF) model in both years and dominated by secondary aerosols, respectively contributing 39% and 41% to PM. The decreasing concentrations (with reductions of 17%-61%) of the secondary source, coal combustion, soil dust and biomass burning largely accounted for the reduction in PM, as a consequence of the recent abatement measures. By contrast, contributions of vehicle-related emissions, similar to the increasing contribution of vehicles at sites in NCP after 2013, should receive increased attention.
华北中部平原（NCP）是京津冀（BTH）地区空气污染的最重要来源地之一。自 2017 年以来，国家政府已发布减排措施，以改善该地区的空气质量。为了检验控制措施的效果，我们在 NCP 的一个城市进行了 PM 特征的观测分析，以研究 PM 质量浓度、化学组成和排放源的变化。2017 年至 2019 年，年 PM 浓度显著降低了 16%，表明空气质量有了实质性改善。秋冬季 PM 富集，主要由 SNA（硫酸盐、硝酸盐和铵盐之和；约 38%）组成，其次是有机碳物质（OM；约 24%）和细土（FS；约 12%）。这种化学成分与 NCP 内一个特大城市（北京）的化学成分不同，其中 OM 与 SNA 相当。约一半的 SNA 归因于硝酸盐，表明 SNA 由硫酸盐驱动转变为硝酸盐驱动，且燃煤切断的影响相当大，其中硫酸盐被浓缩。2018 年至 2019 年，PM 中 SNA 质量分数减少，OM 分数增加，这在一定程度上导致了 PM 的减少。随着污染程度从清洁到严重污染的升高，观察到 SNA 中异质形成的贡献逐渐增加，而 OM 的贡献减少。正矩阵因子化（PMF）模型在这两年中识别出六个来源（土壤尘、生物质燃烧、二次排放、道路交通、燃煤和工业），分别对 PM 贡献 39%和 41%，主要为二次气溶胶。由于最近的减排措施，二次源、燃煤、土壤尘和生物质燃烧的浓度（减少 17%-61%）降低，是 PM 减少的主要原因。相比之下，应更加关注车辆相关排放的贡献，这与 2013 年后 NCP 站点车辆数量的增加贡献相似。
