Mercury Pollution Of Surface Sediment In Dongping Lake

Mercury pollution has long been an important subject in the international environmental science fields,owing to the characteristics of permanentness, eco-toxicity and biological enrichment.Dongping lake is one of the most important reservoirs in the South to North Water Project.In this thesis,surfacial sediment of Dongping lake was investigated.Distribution,speciation and grain-size effect of mercury,as well as influence of organic matter on mercury's geographical behavior were analysed systemically.1.The results show that mercury's content of all samples in Dongping lake are between 91～206μg/kg,in which the maximum appears in Hunan point and the minimum in Wangtai bridge point.The analysis of positive relationships among heavy metals in surficial sediments indiciate that the correlation is all right between Hg with Cr,Ni,Cu,Zn,which show those heavy metals have the same source of man-made pollution.2.According to speciation analysis,the acid extractable fraction and the reductive fraction of mercury occupied a large percentage of the amount in all samples.It suggested that mercury in Dongping lake was potentially harmful to environment.The contents of species of Hg in each sampling point are inequable., which assume wave fluctuation along with the current direction.Furthermore, the maximum value exists in Hunan point,and the minimum value mainly exist in Wangtai bridge and Chenshankou point.3.The species content of mercury doesn't manifest the tendency of decreasing with the rising of thr grain size.It shows that the mercury concentration of different grain sizes depend mainly on the content of mercury in protomineral and different adsorption affected by granularity effect.So when we predict the hazardous impact of different grain sizes,we should think about the percentage, density and mercury content comprehensively.4.The adsorption characteristics and kinetics of humic acids(HAs)to mercury in aqueous solution was studied using static adsorbing method,and the influence of pH on adsorption capacity was also focused on.The results show that the equilibrium adsorbing amount(qe)increases whit the addition of temperature below 20℃,whereas the temperature hardly affects the sorption above 20℃.The adsorbility is optimal in the range of pH 5～9.The adsorption process follows a pseudo second-order kinetic rate equation.The Freundlich isotherm model described the equilibrium data well.The adsorption activation energy of mercury on humic acids is 20.37kJ/mol,which indicates that it belongs to chemiadsorption.