南京2013年冬季三级分粒径雾水化学特征

为研究南京冬季不同粒径雾滴的化学成分的特征,利用three-stage CASCC主动式分档雾水采集器,于2013年12月7日~12月9日南京郊区发生浓雾期间,分时段采集三级分档雾水样本,分档粒径为4~16μm(三级)、16~22μm(二级)、>22μm(一级),共计23个分档雾水样本;用瑞士万通850professional IC型色谱仪器测定水溶性阴、阳离子浓度,分析探讨了三级分粒径雾水中阴、阳离子组分的分布特征,不同粒径雾滴中阴、阳离子浓度的相关性,雾水离子浓度与污染气体以及微物理之间的关系.结果表明,南京雾水的pH值多呈酸性,雾水中的各离子成分分布都与雾滴的大小存在着尺度依赖性关系,小雾滴与大雾滴相比,小雾滴中主要离子成分浓度(NH4+,NO3-,SO42-)高、pH值小且电导率(EC)值高.同时南京雾水中的各离子浓度呈现出夜间高白天低.统计分析显示,南京雾过程中雾水组分的变化,主要源于污染源的贡献差异.结合雾滴谱和污染气体资料分析得出,雾水化学组成的变化与微物理特征以及空气中污染气体有关.

Chemical characteristics of the three-stage fog water in the winter of 2013 in Nanjing

In order to understand the chemical characteristics of fog water in Nanjing, three-stage Caltech Active Strand Cloud Collector (CASCC) was used to collect fog droplets in three separate droplet size ranges (from December 7th to December 9th. 2013). Fifty percent droplet size cuts of 22, 16, and 4 μm diameter are featured in stages one, two and three, respectively. Twenty-three fog samples were collected in two fog events and divided into eight periods. Concentrations of cations and anions in each sample were detected by ion chromatography. Composition of the fog water, chemical composition distribution characteristics of fog water in each stage, the correlation of ions in each stages and the relationship between ion concentrations and gaseous pollutants or microphysics were considered together during the analysis. The results showed the pH mostly resided in acidic range. The three-stage CASCC data showed significant size-dependence for all reported species. The small drop fraction had significantly high concentrations of the major ions (NH4+, NO3-, SO42-), lower pH values and higher EC values than the large drop fraction. Also the data showed concentrations of the species was higher at night. Due to the differences in contribution from regional pollutant sources, soluble components varied greatly in different fog events. Also the ionic composition had a significant relationship with microphysical properties and pollutant gases.