北京市大气PM2.5中四种水溶性阴离子的水平变化比较

了解北京市城区和郊区大气细颗粒物中的四种水溶性阴离子F-、Cl-、SO42-、NO3-的浓度水平,并分析影响其水平高低的因素。使用聚四氟乙烯滤膜分别采集北京市城区和郊区大气中的PM2.5,用纯水提取后采用离子色谱法测定水溶性阴离子质量浓度。采样期间北京市大气PM2.5、F-、Cl-、SO42-和NO3-质量浓度几何均数分别为55.36、0.02、0.46、6.72和1.09μg·m-3,四种水溶性阴离子质量浓度总和占PM2.5质量浓度的19.14%;同一季节(春季)郊区监测点大气PM2.5、SO42-和NO3-质量浓度显著高于城区监测点;城区大气PM2.5与四种水溶性阴离子质量浓度秋季高于春季,但差异无统计学意义;大气PM2.5与Cl-、SO42-和NO3-质量浓度均高度相关。Cl-、SO42-、NO3-是北京市大气PM2.5的重要组成成分。

Comparison of levels of four water-soluble ionic species in ambient PM2.5 in Beijing

Objective This study was conducted to understand the levels and influencing factors of four water-soluble ionic species,F-,Cl-,SO42-,and NO3-,in ambient fine particles with aerodynamic diameter ≤2.5 micrometers(PM2.5) in Beijing.Methods Polytetrafluoroethylene filters were used to collect ambient PM2.5 in an urban and a suburban area of Beijing.Ionic species were extracted from PM2.5 using super pure water and measured by ion chromatography.Results Geometric mean mass concentrations(ug.m-3) of ambient PM2.5 and F-,Cl-,SO42-and NO3-in particles over the entire sampling period were 55.36,0.02,0.46,6.72 and 1.09,respectively.The four water-soluble ionic species accounted for 19.14% of the total PM2.5 mass.In the spring season,the levels of ambient PM2.5,SO42-and NO3-were significantly higher in the suburban area than in the urban area where the levels of PM2.5 and four water-soluble ionic species were higher in the fall than in the spring in the urban area although the differences were not statistically significant.The ambient PM2.5 was highly correlated with Cl-,SO42-and NO3-.Conclusion Three ionic species,Clˉ,SO42-,and NO3?,were important compositions of ambient PM2.5 in Beijing.