Release Mechanism Of Heavy Metals From Sediments In Wuliangsuhai Under Environmental Changes

Heavy metal pollution in sediments in lake has always been one of the environmental issues that many scholars at home and abroad pay close attention to.Heavy metals enter the lake water in a variety of ways,and are enriched in bodies of water,sediments,and microorganisms,thereby affecting the quality of lake water and the water ecosystem.In this paper,Wuliangsuhai,Inner Mongolia Autonomous Region,was studied to study the total amount,form and potential ecological risk of heavy metals(Cu、 Pb、 Cr and Zn)in the ice-season and non-ice-seasonite sediments.The release and dynamics of heavy metals in sediments under natural conditions were discussed.Analysis,and then studied the release of heavy metals in the sediments of Wuliangsuhai under environmental changes and the characteristics of heavy metal morphological changes.Finally,combined with the actual situation,the control range for controlling the release of heavy metals from sediments of Wuliangsuhai was given.The paper draws the following conclusions:Both Cu and Pb,Cr and Zn in the ice-season and non-ice-seasonite did not exceed the first-grade standard of the Soil Environmental Quality Standard(GB15618-1995),and the total amount of heavy metals、(B1+B2+B3)(Acid extractable + Iron-manganese oxide bonding state + Organic matter and sulfide binding state)the heavy metal content and migration of heavy metals in the iceseason are generally greater than non-ice-seasonite.The total amount and form of heavy metals are in a low-risk state during both the ice-sealing and non-icesealing periods.The fitting of heavy metals with different kinetic equations shows that Cu is best fitted with the second-order reaction kinetic equation,Pb is best fitted with the parabolic diffusion equation,and Cr and Zn are best fitted with the double-constant equation.The correlation coefficient is above 0.96.There was a trend of negative correlation between the release of heavy metals and p H(4~9)in sediments.Before and after release,the morphology of Cr and Cu changed little,and they all existed in a stable residue state.The combination of acid and extractable iron and manganese oxides of Zn and Pb.State and organic matter and sulfide bound state content change greatly.The release of heavy metals Cu and Zn in sediments increased with the increase of salinity(0.5g/L~5.0g/L),and the release of Cr and Pb first increased and then decreased until balance.Before and after release,Cr is still stable,mainly in the residue state.Besides the residual state of Cu and Zn,the other three states change more,and the factors that affect the release of Pb are more complicated.The temperature(5℃ ~45℃)has a positive correlation with the release of heavy metals from sediments.At the temperature of 45 °C,the release is greatest.The temperature mainly affects the acid extractable state of heavy metals and organic matter and sulfide bound states.For the current study period,the sediments of the Wuliangsuhai Lake are the “sources” of heavy metals in the water environment,and most of the sampling sites are diffused by the sediments overlying water bodies.According to the actual situation of lake water environment,p H and temperature have little effect on the release of heavy metals in sediments.Salinity has a certain influence on the release of heavy metals in sediments,and the lake water salinity should be strictly controlled below 1.5 g/L.Thus reducing the risk of heavy metal release.