北京东北部城区大气细粒子与相关气体污染特征研究

于2008年7月~2009年4月的4个季节,在北京市朝阳区北部,利用VAPS通用型大气污染物采样仪(URG3000K)对大气细粒子(PM2.5)和环境空气中相关气体进行了同时采集,并利用IC离子色谱仪(DX-600型)分析了PM2.5中水溶性无机离子成分和环境空气中相关气体的含量.结果表明,PM2.5质量浓度春季>夏季>冬季>秋季;SO42-、NO3-和NH4+是PM2.5中最主要的3种水溶性无机离子,年均质量浓度分别为14.82μg/m3、11.57μg/m3和8.35μg/m3,三者浓度之和占PM2.5中总水溶性无机离子浓度的86.28%.SO42-、NH4+浓度占PM2.5浓度百分比均为夏、秋季高于冬、春季; NO3-浓度占PM2.5浓度的百分比为秋季>春季>夏季>冬季.空气中的SO2、NO2和NH3等气态污染物的含量直接影响PM2.5中二次离子SO42-、NO3-和NH4+的浓度, SO2、NO2浓度的季节特征为冬、春季高于夏、秋季,与SO42-、NO3-的季节变化规律相反; NH3浓度在夏季最高,冬季最低. PM2.5酸度在夏、秋季高于冬、春季,且夏、秋季PM2.5样品全部呈酸性,冬、春季PM2.5样品一部分呈酸性,一部分呈碱性.夏季SOR值和NOR值分别为冬季的4.8倍和3倍,表明夏季SO2和NO2更易转化生成SO42-和NO3-.PM2.5中SO42-、NO3-和NH4+主要以(NH4)2SO4、NH4NO3的形式共存于气溶胶体系中.

The pollution characteristics of the atmospheric fine particles and related gaseous pollutants in the northeastern urban area of Beijing

Simultaneous measurements of water-soluble inorganic ions in PM2.5 and related gaseous pollutants in the four seasons from July 2008 to April 2009 were made by using a Versatile Air Pollutants Sampler (URG-3000K) and a DX-600 Ion Chromatography in the northeastern urban area of Beijing. Results showed that the seasonal variation of the mass concentrations of PM2.5 had the characteristics of Spring>Summer>Winter>Autumn. SO42-、NO3- and NH4+ were the three major ions in PM2.5, their annual concentrations were 14.82 μg/m3, 11.57 μg/m3 and 8.35 μg/m3, respectively, accounting for 86.28% of the total mass of water-soluble inorganic ions in PM2.5. The proportions of SO42-、NH4+ in PM2.5 were higher in summer and autumn than in winter and spring, respectively. The seasonal variation of the proportions of NO3- in PM2.5 had the characteristic of Autumn>Spring>Summer>Winter. The concentration of gaseous pollutants, such as SO2、NO2 and NH3 in the ambient air have direct influence on the mass concentration of SO42-、NO3- and NH4+ in PM2.5. The seasonal variation characteristics of SO2 and NO2 were similar, both higher in winter and spring than in summer and autumn, which were different from the seasonal variation characteristics of SO42- and NO3- in PM2.5; whereas, the concentration of NH3 was highest in summer, and lowest in winter. The acidity of PM2.5 in summer and autumn were higher than in winter and spring; all of the PM2.5 samples in summer and autumn were acidic, while part of the PM2.5 samples in winter and spring were acidic, and others were alkaline. The values of SOR and NOR in summer were 4.8 times and 3 times of that in winter, respectively, which indicated that the conversion of SO2 to SO42- in PM2.5 and the conversion of NO2 to NO3- in PM2.5 were more likely to occur during summer than during winter, SO42-、NO3- and NH4+ in PM2.5 coexisted in the forms of (NH4)2SO4 and NH4NO3 in the atmospheric aerosols.