北京冬季一次重污染过程PM2.5中水溶性无机盐的变化特征

为了解北京冬季重污染过程大气颗粒物化学特性,利用高时间分辨率实时在线细粒子快速捕集及化学成分分析系统(RCFP-IC)对2011年2月18—24日发生的一次重污染过程PM2.5中水溶性无机离子浓度变化进行了在线观测.结合颗粒物质量浓度、气态污染物浓度及气象资料,对此次污染过程中污染物的化学成分变化特征进行了详细分析.结果表明,此次北京冬季重污染4 d中颗粒物污染严重;总水溶性无机离子平均质量浓度151.31μg·m-3,占PM2.5相对比例54%,其中NO3-、SO24-和NH4+质量浓度占总水溶性无机离子质量浓度91%,二次离子污染非常严重;硝酸根氧化率(NOR)和硫酸根氧化率(SOR)结果显示NO3-与SO24-主要通过非均相反应生成,水溶性无机盐存在形态以NH4HSO4和(NH4)2SO4为主;重污染期K+和Cl-质量浓度显著升高,Mg2+和Ca2+质量浓度下降;阳、阴离子电荷比(C/A)重污染平均值为0.8,细粒子偏酸性.

The variation of water-soluble inorganic ions during a heavy pollution episode in winter, Beijing

To investigate the chemical characteristics of heavy atmospheric pollution of particulate matter in Beijing,the concentrations of water-soluble inorganic ions were observed using the rapid collection of atmospheric particles and the chemical component online analysis system(RCFP-IC) from 18 to 24 February,2011 during a heavy pollution episode.Combined with the mass concentration of particulate matter,gaseous pollutant concentrations and meteorological data,we analyzed the characteristics of water-soluble inorganic ions in detail for this episode.The results showed that particulate pollution was serious during 4 days of this winter heavy pollution in Beijing.The total concentration of water-soluble inorganic ions was 151.31 μg·m-3 and the relative proportions of PM2.5 was 54%,of which more than 90% was from NO-3,SO2-4 and NH+4.NOR and SOR showed that NO-3 and SO2-4 were generated through the heterogeneous reaction.Water-soluble inorganic salts mainly existed in the form of NH4HSO4 and(NH4)2SO4.The concentrations of K+ and Cl-increased significantly,while Mg2 + and Ca2 + showed an opposite trend during the heavy pollution episode.The average of C/A was 0.8.Fine particles showed acidity.