School of Safety and Environmental Engineering, Capital University of Economics and Business,No.121 Zhangjialukou Rd, Fengtai District, Beijing 100070, PR China.
College of Environmental Science and Engineering, Peking University, No.5 Yiheyuan Rd, Haidian District, Beijing 100871, PR China.
Sci Total Environ. 2017 Apr 15;584-585:523-534. doi: 10.1016/j.scitotenv.2017.01.060. Epub 2017 Jan 25.
Chongqing, the largest megacity in southwest China, faces serious aerosol pollution but lacks information on particle characteristics and its sources. Official data released by Chongqing Environmental Protection Bureau demonstrated that urban PM concentrations decreased remarkably from 150μgm in 2000 to 90μgm in 2012. However, only several peer-reviewed studies paid attention to local fine particle (PM) pollution. In the study, PM samples were obtained and subjected to chemical analysis in an urban site of the city during 2012 to 2013. The annual mean PM and PM concentrations in urban Chongqing were 103.9±52.5 and 75.4±42.2μgm, respectively. PM showed a distinct seasonality of high concentration in winter and similar levels in other seasons. The average OC/EC (organic carbon/element carbon) ratio was 3.7 with more high-OC/EC ratio sources contribution in autumn and winter. The varying sources and formation mechanisms resulted in SO and NH peaks in both summer and winter, whereas high nitrate concentration was only observed in winter. In the average mass closure, PM was composed of 23.0% SO, 11.7% NO, 10.9% NH, 30.8% OM (organic matter), 5.2% EC, 8.2% mineral dust, 0.6% TEO (trace elements), 1.0% Cl and 1.1% K, while exhibiting large seasonal variability. Using positive matrix factorization (PMF), six sources were apportioned in PM: secondary inorganic aerosols, coal combustion, other industrial pollution, soil dust, vehicular emission, and metallurgical industry. The annual mean contribution of above sources to PM was 37.5, 22.0, 17.5, 11.0, 9.8 and 2.2%, respectively. Coal combustion was identified by As tracer and dominated the primary sources of PM, while the two different industrial sources were characterized by Cr and Mo, Co, Ni, and Se, respectively. The study is of great importance in characterizing the historical trends, current chemical characteristics and sources of fine particles in urban Chongqing.
中国西南最大的特大城市重庆面临严重的气溶胶污染，但缺乏有关颗粒特征及其来源的信息。重庆环境保护局发布的官方数据显示，城市 PM 浓度从 2000 年的 150μg/m3显著下降至 2012 年的 90μg/m3。然而，仅有少数经过同行评审的研究关注当地的细颗粒物 (PM) 污染。在本研究中，于 2012 年至 2013 年在城市的一个城区采集了 PM 样本并进行了化学分析。城市重庆的年平均 PM 和 PM2.5 浓度分别为 103.9±52.5 和 75.4±42.2μg/m3。PM 表现出冬季浓度高、其他季节浓度相似的明显季节性特征。OC/EC（有机碳/元素碳）比值的平均值为 3.7，秋冬季高 OC/EC 比值的来源贡献更多。不同的来源和形成机制导致夏季和冬季均出现 SO 和 NH 的峰值，而只有冬季硝酸盐浓度较高。在平均质量封闭中，PM 由 23.0%的 SO、11.7%的 NO、10.9%的 NH、30.8%的 OM（有机物质）、5.2%的 EC、8.2%的矿物尘、0.6%的 TEO（微量元素）、1.0%的 Cl 和 1.1%的 K 组成，同时表现出较大的季节性变化。使用正定矩阵因子分解 (PMF)，将 PM 分配到六个来源：二次无机气溶胶、煤燃烧、其他工业污染、土壤尘、车辆排放和冶金工业。上述来源对 PM 的年平均贡献分别为 37.5%、22.0%、17.5%、11.0%、9.8%和 2.2%。As 示踪剂表明煤燃烧是主要的 PM 来源，而两个不同的工业来源分别以 Cr 和 Mo、Co、Ni 和 Se 为特征。该研究对于描述重庆城市细颗粒物的历史趋势、当前化学特征和来源具有重要意义。
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