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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