中文关键词PM_2.5水溶性无机离子季节特征演化特征源解析北京 英文关键词PM_2.5water-soluble inorganic ionsseasonal characteristicsevolution characteristicssource apportionmentBeijing

作者	单位	E-mail
李欢	西南交通大学地球科学与环境工程学院, 成都 611756	751566146@qq.com
唐贵谦	中国科学院大气物理研究所, 大气边界层物理与大气化学国家重点实验室, 北京 100029
张军科	西南交通大学地球科学与环境工程学院, 成都 611756	zhangjunke@home.swjtu.edu.cn
刘琴	西南交通大学地球科学与环境工程学院, 成都 611756
闫广轩	河南师范大学环境学院, 黄淮水环境污染与防治教育部重点实验室, 河南省环境污染控制重点实验室, 新乡 453007
程萌田	中国科学院大气物理研究所, 大气边界层物理与大气化学国家重点实验室, 北京 100029
高文康	中国科学院大气物理研究所, 大气边界层物理与大气化学国家重点实验室, 北京 100029
王迎红	中国科学院大气物理研究所, 大气边界层物理与大气化学国家重点实验室, 北京 100029
王跃思	中国科学院大气物理研究所, 大气边界层物理与大气化学国家重点实验室, 北京 100029

中文摘要 为探究近年来北京市空气质量持续改善过程中PM_2.5及其中水溶性无机离子（WSIIs）特征，于2017~2018年在北京城区进行了连续1 a的PM_2.5样品采集，对其中9种主要WSIIs进行了全面分析.结果表明，北京市PM_2.5年均浓度为（77.1±52.1）μg ·m^-3，最高和最低值分别出现在春季[（102.9±69.1）μg ·m^-3]和夏季[（54.7±19.9）μg ·m^-3].WSIIs年均浓度为（31.7±30.1）μg ·m^-3，对PM_2.5贡献比例为41.1%，季节贡献特征为：秋季（45.9%） > 夏季（41.9%） > 春季（39.9%） ≥ 冬季（39.2%）.SNA是WSIIs的重要组成，春、夏、秋和冬季在总WSIIs中的占比分别可达86.0%、89.5%、74.6%和73.0%.随温度升高，NO₃^-和SO₄^2-分别呈现出了先升高后降低以及波动性升高的趋势；而当相对湿度低于90%时，2种离子浓度均随相对湿度增加而升高，反映了光化学和液相过程对2种离子组分的贡献差异.随污染加重，WSIIs整体贡献比例大幅升高，且各类WSIIs演化特征各异，其中，NO₃^-浓度和贡献均持续升高，而SO₄^2-和各类源自扬尘的离子组分（Mg²⁺、Ca²⁺和Na⁺）贡献降低.观测期间WSIIs主要来源包括二次转化、燃烧源和扬尘源，对燃煤和机动车的管控是其减排的重要途径.后向轨迹分析表明，源自北京市南部和西部的气团对应着较高的PM_2.5浓度和WSIIs占比，且二次离子贡献显著；而源自西北和北部的气团对应的PM_2.5浓度和WSIIs占比则较低，但Ca²⁺贡献较高. 英文摘要 To explore the characteristics of water-soluble inorganic ions (WSIIs) in PM_2.5 during the process of continuous improvement of air quality in Beijing in recent years, a continuous collection of PM_2.5 sample campaign was conducted in Beijing from 2017 to 2018. The PM_2.5 mass concentration and WSIIs were then determined. The results showed that the average concentration of PM_2.5 in Beijing was (77.1±52.1) μg ·m^-3, with the highest and lowest values during spring [(102.9±69.1) μg ·m^-3]and summer [(54.7±19.9) μg ·m^-3], respectively. The average concentration of WSIIs was (31.7±30.1) μg ·m^-3, accounting for 41.1% of the PM_2.5 mass, and the seasonal contributions were: autumn (45.9%) > summer (41.9%) > spring (39.9%) ≥ winter (39.2%). SNA was an important component of the WSIIs that accounted for 86.0%, 89.5%, 74.6%, and 73.0% of the total WSIIs during spring, summer, autumn, and winter, respectively. With an increase in temperature, the concentration of NO₃^- increased initially and then decreased, while the concentration of SO₄^2- increased. When the relative humidity was less than 90%, the concentrations of both NO₃^- and SO₄^2- increased with an increase in relative humidity. With the aggravation of pollution, the overall contribution of WSIIs in PM_2.5 increased significantly, and the evolution characteristics of different ions were different. Among them, the concentration and contribution of NO₃^- continued to increase, while the contributions of SO₄^2- and the ions from dust (Mg²⁺, Ca²⁺, and Na⁺) decreased. During the observation period, the primary sources of WSIIs were secondary conversion, combustion source, and dust. The control of coal combustion and motor vehicles is critical to reduce the emission of WSIIs. The backward trajectory analysis showed that the air masses from the south and west of Beijing corresponded to the high PM_2.5 concentration and proportion of WSIIs, and the contribution of secondary ions was significant. However, the concentrations and proportions of the air masses from the northwest and north were relatively low, but the contribution of Ca²⁺ was high.

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