| The coal-fired power plant(CFPP)is one of the most prominent regional anthropogenic sources of heavy metals.Heavy metals discharged from CFPP get into the atmosphere with flue gas and enter into soil by dry and wet deposition,eventually,endanger human beings health through the food chain.Therefore,it is significant and meaningful to explore the environmental situation which affected by the emission of mercury(Hg)and lead(Pb)from CFPP.A research about the CFPP located in the coastal area of southeastern China was conducted to analyze the distribution characteristics and to explore the transfer and transformation rules of Hg and Pb in different environmental media,and the lead isotope composition of different kinds of samples were used to analyze the contribution of the CFPP to regional lead pollution.The research results are summarized as follows:(1)Hg and Pb contents in the atmospheric particulates were far more than in the fly coal ashes,indicating that the atmospheric particulates possess the function of Hg and Pb enrichment.Hg and Pb concentrations in wet deposition had distinct seasonal variation.For Hg,the concentration is higher in summer than in winter,but for Pb,the concentration is higher in winter than in summer.For the first batch of sample of atmospheric particulates(PM2.5 and PM10)and wet deposition,the Hg contents in wet deposition and PM2 5 showed a significant positive correlation(r=0.754,p<0.05),however,there was no significant correlation with PM10(p>0.05).(2)Hg was enriched in the top soil and the concentration decreased with the depth of the soil layer.Top soil THg concentration had significant positive correlation with inhalable particles PM2.5(r=0.719,p<0.05),while there was no significant correlation with another kind of inhalable particles PM10(p>0.05).For Pb,Pb content increased with the depth of the soil layer.The distribution of the chemical form of Hg in the top soil is:residuals>oxidizable>reducible>acid exchangeable,and the mean methylation rate of mercury in the top soil was 2.67%.The distribution of the chemical form of Pb in the top soil is:residuals>reducible>oxidizable>acid exchangeable.(3)The mean value of Hg content in the grains of wheat was 25.78 ng/g,and the mean methylation rate of mercury was 4.18%;the mean value of Pb content in the grains of wheat was 1.05 mg/kg.According to the state threshold limits in GB2762-2012,the over-limit ratios were 75%and 100%,respectively.THg contents in soil had significantly positive correlation with THg concentrations of roots of wheat(r=0.678,p<0.05),while there was no significant correlation between THg contents in soil and the concentrations of grains of wheat(p>0.05),suggesting that the Hg from soil was not the primary source of Hg in grains of wheat.Acid exchangeable Hg was significantly positively correlated with Hg contents in roots of wheat(r=0.776,p<0.01),indicating acid exchangeable Hg had higher availability for the wheat.(4)Ratios of Pb isotopes were used to explore the sources of Pb in environmental media.The contributions of Pb in fly coal ashes to the atmospheric particulates were 57.92%and 40.86%in winter and summer,respectively.And the contributions to the atmospheric wet deposition were 66.17%in winter and 57.51%in summer,respectively.The contribution of CFPP to the soil is 65.65%,indicates that the CFPP is a primary source of soil-Pb.For the grains of wheat,the contribution of the Pb in atmospheric particulates(80.82%)was significantly more than the soil(19.18%). |
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