• 关键词：PM_2.5  水溶性离子  二次转化  季节变化  太原

• 基金项目：国家自然科学基金（No.41807456）；山西财经大学青年科研基金（No.QN-2018010）

• 任娇
• 1. 山西财经大学, 资源型经济转型协同创新中心, 太原 030006;2. 山西财经大学, 资源型经济转型发展研究院, 太原 030006

• 尹诗杰
• 山西财经大学, 资源型经济转型发展研究院, 太原 030006

• 郭淑芬
• 1. 山西财经大学, 资源型经济转型协同创新中心, 太原 030006;2. 山西财经大学, 资源型经济转型发展研究院, 太原 030006

• 摘要：为探究当前空气质量持续改善背景下重污染地区大气PM_2.5和水溶性无机离子（WSⅡs）的污染特征和季节变化，于2019年在太原市采集了四季PM_2.5样品.结果表明，2019年太原市PM_2.5年均质量浓度为（65.50±30.44）μg·m^-3，水溶性离子浓度的季节特征为：冬季（39.81 μg·m^-3） > 秋季（33.05 μg·m^-3） > 春季（20.50 μg·m^-3） > 夏季（19.62 μg·m^-3）.WSⅡs以二次离子SNA为主，占总离子浓度的76.90%±10.51%，且随着PM_2.5污染加重，SNA的比重显著升高.其中，SO₄^2-和NO₃^-在秋、冬季的浓度最高，这与气态污染物排放增加和二次转化程度的升高（硫氧化率SOR>0.30，氮氧化率NOR>0.10）有关；NH₄⁺、Cl^-和K⁺在冬季的浓度最高，是其他季节的1.2~7.9倍，可能归因于冬季燃煤和生物质燃烧活动的增加；由于春季风速较高，受土壤扬尘的影响，Ca²⁺和Mg²⁺的比重在春季显著增加为20.2%.春季和夏季为贫氨状态，而秋、冬季为富氨状态，且硝酸盐颗粒物在高湿度条件下的吸湿增长比硫酸盐更为显著.太原市大气PM_2.5中水溶性离子主要来源于二次生成、燃煤、生物质燃烧和土壤扬尘.

• Abstract：In order to explore the characteristics and seasonal variation of PM_2.5 and water-soluble ions in heavily polluted areas under the background of continuous improvement of air quality, PM_2.5 samples from four seasons were collected in Taiyuan in 2019. The results showed that the average annual mass concentration of PM_2.5 in Taiyuan was (65.50±30.44) μg·m^-3, and the seasonal characteristic of water-soluble ion concentration was:winter (39.81 μg·m^-3) > autumn (33.05 μg·m^-3) > spring (20.50 μg·m^-3) > summer (19.62 μg·m^-3). SNA was the dominant component of the water-soluble ions, accounting for 76.90%±10.51%, and the percentage of SNA in WSⅡs increased significantly with the aggravation of PM_2.5 pollution. The concentration of SO₄^2- and NO₃^- was the highest in autumn and winter, which is related to the increase of primary emission of gaseous pollutants and secondary transformation rate with SOR>0.30 and NOR>0.10. The concentrations of NH₄⁺, Cl^- and K⁺ were the highest in winter, which is 1.2~7.9 times higher than that of other seasons, which may be attributed to the increase of coal and biomass burning activities in winter. Due to the high wind speed in spring and the influence of soil dust, the proportion of Ca²⁺ and Mg²⁺ in WSⅡs increased significantly to 20.2% in spring. It was ammonia-poor in spring and summer, and ammonia-rich in autumn and winter. Moreover, the moisture absorption growth of nitrate particles under high humidity was more significant than that of sulfate. The water-soluble ions in PM_2.5 in Taiyuan city mainly come from secondary generation, coal and biomass burning, and soil dust.

• Key words：PM_2.5  water-soluble ions  secondary transformation  seasonal variation  Taiyuan

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