上海市浦东新区大气PM2.5中铅及其同位素特征
Lead and its isotope characteristics in atmospheric PM2.5 in Pudong New Area, Shanghai
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摘要:
目的 了解上海市浦东新区大气PM2.5中铅的浓度及同位素特征。
方法 2015年3月—2016年2月从浦东新区5个采样点采集410份大气PM2.5样本。应用电感耦合等离子体质谱法(ICP-MS)测定PM2.5样本中的铅质量浓度及其同位素比值，探讨铅随季节和PM2.5水平不同的变化特征。采用潜在生态危害指数评估铅危害程度。利用铅同位素比值特征初步解析铅的污染来源。
结果 PM2.5的年质量浓度中位数(P25，P75)为60.2(41.7，90.9)μg/m3，铅的年质量浓度中位数(P25，P75)为0.032(0.018，0.053)μg/m3。PM2.5质量浓度与Pb质量浓度呈正相关(r=0.815，P < 0.05)。PM2.5质量浓度(χ2=40.78)和铅质量浓度(χ2=56.77)均存在季节差异(P < 0.05)，冬季高于夏季。不同采样点间铅质量浓度差异无统计学意义(P > 0.05)。铅的潜在生态危害指数为107，显示危害程度为较强。样品204Pb/206Pb、207Pb/206Pb、208Pb/206Pb分别为0.054 79±0.000 28、0.857 32±0.002 93、2.098 91±0.008 41。不同季节铅同位素比值均值之间的差异与同位素比值测量偏差无明显区别。不同空气质量情况下，204Pb/206Pb均值差异、207Pb/206Pb均值差异与同位素比值测量偏差均无明显区别。208Pb/206Pb均值在空气质量为污染时(2.101 59~2.102 07)高于空气质量为优和良(2.097 13和2.097 32)时。
结论 上海市浦东新区PM2.5污染水平较高，但铅污染处于较低水平，PM2.5和铅质量浓度均存在明显的季节差异，铅同位素比值则未见季节差异。铅污染来源主要是水泥的生产使用和燃煤排放，需加强冬季大气PM2.5中铅的监测和预防，重点控制水泥和燃煤铅排放。
Abstract:Objective To evaluate the lead concentration and its isotope characteristics in atmospheric PM2.5 in Pudong New Area of Shanghai.
Methods A total of 410 PM2.5 samples were collected from five monitoring sites in Pudong New Area from March 2015 to February 2016. The lead concentration and its isotope ratios in the PM2.5 samples were determined by inductively coupled plasma mass spectrometry (ICP-MS), and their changing characteristics with different seasons and PM2.5 concentrations were analyzed. The health risk of lead was assessed by applying potential ecological risk index. The source identification of lead was preliminarily explored using its isotope ratios.
Results The medians (P25, P75) of annual mass concentrations of PM2.5 and lead were 60.2 (41.7, 90.9) μg/m3 and 0.032 (0.018, 0.053) μg/m3, respectively. The PM2.5 concentration was positively correlated with the lead concentration (r=0.815, P < 0.05). Both the concentrations of PM2.5 (χ2=40.78) and lead (χ2=56.77) showed seasonal variations (P < 0.05) and were higher in winter than in summer. No differences in lead concentrations were found among the selected monitoring sites (P > 0.05). Lead was graded as relatively high potential ecological risk, with an index of 107. The isotopic ratios were 0.054 79±0.000 28, 0.857 32±0.002 93, and 2.098 91±0.008 41 for 204Pb/206Pb, 207Pb/206Pb, and 208Pb/206Pb, respectively. There were no significant differences between the mean differences of lead isotope ratios and the deviation of isotope ratio measurements in different seasons. There were no significant differences between the mean differences and the deviation of isotope ratio measurements for 204Pb/206Pb and 207Pb/206Pb under different air quality conditions. The mean 208Pb/206Pb was higher when air quality was polluted (2.101 59-2.102 07) than when air quality was excellent and good (2.097 13 and 2.097 32).
Conclusion A high PM2.5 pollution level and a low lead pollution level are identified in Pudong of Shanghai. PM2.5 and lead concentrations both show seasonal variations, but no seasonal variations in lead isotope ratios are observed. The main sources of lead pollution in the selected area are cement production and coal combustion, which requires strengthened monitoring and prevention of lead pollution in atmospheric PM2.5 in winter and strict control of lead emissions from cement production and coal combustion.
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