Du Xiang, Zhao Pu-Sheng, Su Jie, Dong Qun
Institute of Urban Meteorology, China Meteorological Administration, Beijing 100089, China.
State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
Huan Jing Ke Xue. 2018 Nov 8;39(11):4858-4865. doi: 10.13227/j.hjkx.201802146.
A micro-orifice uniform deposit impactor (MOUDI-122) was used to collect ambient aerosol at an urban site in Beijing in both winter and summer from 2016 to 2017. The water-soluble components, including ions and water-soluble organic carbon (WSOC) were analyzed. The characteristics of concentrations and size distributions for water-soluble components under different seasons and pollution conditions were determined. The results showed that NH, NO, SO, and K in both seasons and Cl in winter mainly distributed in the accumulation mode, and Mg and Ca primarily distributed in the coarse mode. The secondary ions were still the main components of PM in Beijing. The concentrations of SO were higher in summer, whereas those of NO, K, and Cl were higher in winter. Mg and Ca had lower correlations with other main components of aerosols, indicating their independent sources. The average size distributions and concentration levels of NO and SO exhibited apparent differences between daytime and nighttime in summer. During polluted periods, the concentrations of secondary ions increased in both the accumulation and coarse modes but decreased in the Aitken mode. As pollution levels increased in winter, the mass median diameters of secondary ions in the droplet mode also increased. The WSOC concentration and particle size distribution under accumulation mode in summer were significantly larger than those in winter. The distribution peaks of WSOC in accumulation mode were higher in summer than those in winter. The WSOC in particles of 0.056-0.32 μm were relatively stable under different pollution levels. However, the WSOC concentration in particles larger than 0.32 μm during polluted periods was evidently higher than that during clean periods.
2016年至2017年冬夏两季，在北京城区使用微孔均匀沉积冲击器（MOUDI-122）采集环境气溶胶。分析了包括离子和水溶性有机碳（WSOC）在内的水溶性成分。确定了不同季节和污染条件下水溶性成分的浓度和粒径分布特征。结果表明，冬夏两季的NH、NO、SO和K以及冬季的Cl主要分布在积聚模态，而Mg和Ca主要分布在粗模态。二次离子仍是北京PM的主要成分。夏季SO浓度较高，而冬季NO、K和Cl浓度较高。Mg和Ca与气溶胶其他主要成分的相关性较低，表明其来源独立。夏季NO和SO的平均粒径分布和浓度水平在白天和夜间存在明显差异。在污染期间，积聚模态和粗模态的二次离子浓度增加，而艾肯模态的二次离子浓度降低。随着冬季污染水平的增加，液滴模态二次离子的质量中值直径也增加。夏季积聚模态下的WSOC浓度和粒径分布明显大于冬季。夏季积聚模态下WSOC的分布峰值高于冬季。在不同污染水平下，粒径为0.056-0.32μm颗粒中的WSOC相对稳定。然而，污染期间粒径大于0.32μm颗粒中的WSOC浓度明显高于清洁期间。
