沙尘天气期间大气PM2.5和PM10中部分元素浓度的变化特征

Feature Analysis of Metal Components of PM2.5 and PM10 during Sand Dust Weather

目的探讨沙尘天气期间大气颗粒物PM2.5和PM10质量浓度的变化及其部分元素浓度的变化特征。方法于2008年4月26日—6月11日,对北京和内蒙古阿拉善盟两地沙尘天气和非沙尘天气期间大气颗粒物进行采样,以重量法计算PM2.5和PM10的日均质量浓度,并用原子吸收光谱法、X荧光分析法对其部分元素浓度进行测定。采用Wilcoxon秩和检验比较沙尘天气和非沙尘天气PM2.5和PM10的质量浓度,采用富集因子分析颗粒物中金属组分的分布特征。结果沙尘天气发生时阿拉善盟大气PM2.5和PM10质量浓度出现相应的峰值,其远高于非沙尘天气PM2.5和PM10的平均值(P<0.05);北京大气PM10质量浓度在沙尘天气高于非沙尘天气(P<0.05),而PM2.5的质量浓度变化差异无统计学意义。且北京和阿拉善盟在沙尘天气和非沙尘天气颗粒物质量浓度的变化趋势相似。阿拉善盟大气PM10中常量元素(K、Ca、Na、Mg)和污染元素(Pb、Cr、Cd、As)的浓度在沙尘天气升高(P<0.05),PM2.5中各元素浓度在沙尘天气升高,但差异无统计学意义。与非沙尘天气比较,沙尘天气北京大气PM10中Cd浓度升高,差异有统计学意义(P<0.05);其他7种元素浓度升高,差异无统计学意义。北京大气PM2.5中Pb、As、Cd、K、Na元素浓度在沙尘天气降低,差异无统计学意义;PM2.5中Cr、Ca、Mg元素浓度在沙尘天气升高,差异无统计学意义。富集因子分析法显示,两个采样点富集因子大于1小于10的元素有Na、Mg、Cr,富集因子大于10的元素有Ca、Pb、As。结论沙尘天气时大气PM2.5和PM10的浓度显著升高;同时,其中的元素浓度在沙尘天气时也有上升的趋势。研究发现,污染元素Pb、As容易在粒径较小的PM2.5中聚集,并且主要受人为活动的影响,可能与沙尘天气无关联。

Objective To study the basic distribution of chemical components of PM2.5 and PM10 in the sand dust weather.Methods PM2.5 and PM10 was collected in Beijing and Alashan during the sand dust weather,from April 26th to June 11th.Daily concentrations of PM2.5 and PM10 were determined with the method of Gravimetric.The chemical components of PM2.5 and PM10 were determined with atomic absorption spectrum and X fluorescence analysis.Results The concentrations of both PM2.5 and PM10 presented an obvious peak when sand dust weather happened.Also the concentration trends of PM2.5 and PM10 were basically the same both in two collected areas during the study time.As a source area of Asian sand dust,the concentrations of K,Ca,Na,Mg and heavy metal elements（Pb,Cr,Cd and As） in PM10 during the sand dust weather were higher than those of non-sand dust weather（P〈0.05）in Alashan.Compared with non-dust weather,when dust weather happened in Beijing,the concentration of Cd in atmospheric PM10 increased significantly（P〈0.05）.The method of enrichment factor（EF） was conducted on chemical components with the result of：1〈EF〈10：Na,Mg and Cr;EF〉10：Ca,Pb and As.Conclusion The concentrations of atmospheric PM2.5 and PM10 are significantly high and the content of some chemical elements in them increases in sand dust weather.Pb and As are likely to enrich in PM2.5,which are influenced by human activities and have no relationship with sand dust weather.