ICP-MS用于北京市PM_(2.5)中铅及其同位素的形态分析

Speciation Analysis of Lead and Its Isotopes in Fine Particulate Matters in Beijing by ICP-MS

对2005年9月至2006年5月所采集的24份北京市PM2.5样品进行序列连续提取,分别得到水溶态、脂溶态和不溶态3个分量的铅;在最佳仪器工作条件下,采用电感耦合等离子体质谱(ICP-MS)测定上述各分量中铅的浓度及同位素比值。采用GBW09133考察铅浓度测定的准确度,并用SRM 981标准铅试剂校正质量歧视效应和仪器漂移。结果表明,采用ICP-MS分析大气PM2.5中不同形态铅浓度及同位素比值的测定数据准确可靠。北京市大气PM2.5样品中水溶态、脂溶态和不溶态3个分量铅的平均百分含量分别为20.69%,0.32%和78.99%;相应的铅同位素比值206Pb/207Pb的均值分别为1.1526,1.1374和1.2193;其中水溶态和不溶态铅的同位素比值具有统计学差异(p<0.01)。同位素比值的比对结果提示,北京市成人血铅可能源于北京市大气PM2.5中水溶态铅而非不溶态铅,故大气细颗粒物中水溶态铅对人体健康的威胁更值得注意。

Fine particulate matters （PM2.5） collected in Beijing during a period from September 2005 to May 2006 were studied. Sequential extraction procedures were applied to divide the total lead into three fractions, i.e. water soluble, liposoluble and insoluble lead. Lead concentrations and their isotopes in each fraction were then determined by inductively coupled plasma mass spectrometry （ICP-MS）. Lead standard reference GBW 09133 was used to investigate the accuracy of lead concentration determination and SRM 981 was used to correct the mass discrimination and instrumental drift. The obtained results showed that the analytical precision of lead isotope ratios for SRM 981 of seven repeat measurements at lead concentration of 10 ng · mL^-1 came to about 0. 34, 0. 27 and 0. 24 percent for the ^206 pb/^204 Pb, ^206 pb/^207 Pb and ^206 pb/^208 Pb ratios, respectively. In Beijing, the mass concentrations for PM2.5 and lead of ambient air were 125.56 and 0. 415 ug · m^- 3 respectively for winter 2005, and 201.6 and 0. 475 ug· m^-3 respectively for spring 2006 on average, resembling those published results. It was indicated that the lead in the PM2.5 existed mainly in insoluble form, which accounted for 78. 99%, while water soluble lead and liposoluble lead amount were 20. 69% and 0. 32%, respectively. The mean values of ^206 pb/^207 Pb ratio for water soluble species and insoluble species were 1. 152 6±0. 009 3 and 1. 219 3 ± 0. 009 1 respectively, with a significant difference （Student ＇s test; p〈0. 01） statically. By comparing ^206 pb/^207 Pb ratios between biological specimen and ambient air samples, the ^206 pb/^207 Pb ratios in water soluble fraction coincided very well with those in adult blood, therefore, water soluble lead but not insoluble lead in PM2. 5 may be the potential source of adults blood lead in Beijing. More attention should be paid to the effect of soluble lead in fine particle matters on human health.