舟山市环境空气PM_(2.5)及水溶性离子污染特征分析

Characteristics of PM_(2.5) and water-soluble ions in ambient air in Zhoushan

为探究舟山市PM_(2.5)及水溶性离子组分的污染特征,于2016年4月、7月、10月和2017年1月在舟山市区3个国控点采集了168个PM_(2.5)样品,利用离子色谱仪测定颗粒物中的9种水溶性离子(Cl^-、NO_3^-、SO_4^(2-)、NH_4^+、K^+、F^-、Na^+、Mg^(2+)和Ca^(2+)),结合气象数据和数值分析手段对舟山市区PM_(2.5)和水溶性离子质量浓度特征、颗粒物酸碱度及二次离子的影响因素(气象参数、前体物)进行研究.结果表明,采样期内,舟山市PM_(2.5)质量浓度时间变化规律为春季>冬季>夏季>秋季,空间分布较为均匀;二次离子是舟山PM_(2.5)主要水溶性组成,且在PM_(2.5)中具有一致的季节变化特征;阴阳离子平衡分析显示舟山市PM_(2.5)整体呈现酸性,并以夏季酸度最低、秋季酸度最高;温度是影响舟山市二次离子浓度的主要气象因素;以燃煤源为主的固定源是舟山市水溶性污染物的主要污染来源,檀枫和临城采样点的SO_4^(2-)和NO_3^-受电厂和燃煤锅炉的污染排放影响严重,普陀区船舶客货运输量大,是普陀点二次离子前体物的主要污染来源.

In order to study the characteristic of atmospheric fine particulate matter (PM2.5) and water-soluble ions in PM2.5 in Zhoushan, 168 PM2.5 samples were collected at three state monitoring stations in Apr.2016, Jul.2016, Oct.2016 and Jan.2017. Concentrations of 9 water-soluble ions (Cl^-、NO3^-、SO4^2-、NH4+、K^+、F^-、Na^+、Mg2+ and Ca^2+) in the samples were measured by ion chromatography. Combined with meteorological data in the area and numerical analysis, PM2.5 and water-soluble mass concentration characteristics, particle acidity as well as secondary ion influencing factors (meteorological parameters, precursors) were studied. The results show that, during the sampling period, the concentration of PM2.5 varied with time, decreasing in the order of spring, winter, summer, and autumn, but has a uniform spatial distribution in Zhoushan. The secondary ions were the main water-soluble composition in PM2.5, and had consistent seasonal variation characteristics. The analysis based on charge balance demonstrated that the aerosol in Zhoushan was overall acidic, with the lowest acidity in summer and the highest acidity in autumn. Temperature was the main meteorological factor that affects secondary ion concentration in Zhoushan. Coal-firing was the main source of water-soluble pollutants in Zhoushan. The SO4^2- and NO3^- at Tanfeng and Lincheng sampling sites were seriously affected by the emissions from power plants and coal-fired boilers. Putuo District, which is featured with a large volume of passenger and cargo transportation, was the major source of pollution for the secondary ion precursors in Putuo sampling site.