| 北京地区气溶胶水溶性组分粒径分布特征 |
| 摘要点击 2155 全文点击 767 投稿时间：2018-02-28 修订日期：2018-04-20 |
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| 中文关键词 气溶胶 水溶性组分 粒径分布 北京 化学组分 |
| 英文关键词 aerosol water-soluble component size distribution Beijing chemical composition |
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| 中文摘要 |
| 2016~2017年，分别在夏季和冬季在北京城区利用微孔均匀分级采样器（MOUDI-122），采集环境气溶胶，并对其中水溶性离子和水溶性有机物开展了定量分析，对主要水溶性组分质量浓度粒径分布特征，以及季节和不同污染状态下的差异进行了讨论.结果表明，NH4+、NO3-、SO42-、K+和冬季Cl-主要分布在积聚模态，Mg2+和Ca2+主要分布在粗粒子模态，NH4+、NO3-、SO42-在积聚模态的质量浓度最高，二次离子仍是北京地区PM2.5污染的主要组分.SO42-在夏季浓度较高，而NO3-、K+、Cl-在冬季明显高于夏季，Mg2+和Ca2+来源较为独立，与气溶胶其他主要组分的相关性较低.夏季NO3-和SO42-浓度昼夜差异显著，白天SO42-浓度水平明显高于夜晚，夜晚NO3-浓度明显高于白天，且主要表现在积聚模态.污染状况下，二次离子在积聚模态和粗模态浓度增加明显，但在爱根模态中浓度降低.冬季随着污染加重，二次离子液滴模态质量中值粒径明显增大.夏季积聚模态WSOC浓度粒径分布峰值粒径明显大于冬季，0.056~0.32 μm粒径段WSOC在不同污染状态下浓度水平基本一致，在0.32 μm以上区间，污染状态下WSOC平均浓度明显高于清洁时段. |
| 英文摘要 |
| 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 NH4+, NO3-, SO42-, and K+ in both seasons and Cl- in winter mainly distributed in the accumulation mode, and Mg2+ and Ca2+ primarily distributed in the coarse mode. The secondary ions were still the main components of PM2.5 in Beijing. The concentrations of SO42- were higher in summer, whereas those of NO3-, K+, and Cl- were higher in winter. Mg2+ and Ca2+ had lower correlations with other main components of aerosols, indicating their independent sources. The average size distributions and concentration levels of NO3- and SO42- 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. |
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