Study On The Characteristics Of Heavy Metal Pollution And Biotoxicity In The Environment Around Smelters

China is one of the countries with the most serious soil pollution in the world.In recent years,the state attaches great importance to the work of soil environmental protection.While the metal smelting industry contributes to the economic development,the dust pollution produced in the production process also causes many practical or potential environmental problems.Therefore,it is of great practical significance to study the soil heavy metal pollution caused by metal smelters,which can provide scientific basis for the prevention and control of heavy metals in soil.In this study,two non-ferrous metal smelters were selected to study the river water,sediment and soil environment around them.Firstly,the total amount of heavy metals in the multi-media environment was measured.On this basis,the farmland soil was mainly studied.The correlation and spatial distribution of seven heavy metals(Cr,Ni,Cu,Zn,Cd,Pb and As)in the soil around two smelters were analyzed by using multivariate statistical analysis method and spatial kriging interpolation method;The potential ecological hazard index method was used to evaluate the ecological hazard of seven heavy metals in soil,and BCR multi-level continuous extraction method and TCLP were used to analyze the occurrence form and leaching toxicity of seven heavy metals in soil.The single and combined toxicity of Cd,Pb and As heavy metals with the most obvious ecological risks were analyzed,the aim is to provide theoretical basis and technical guidance for the remediation of local soil contaminated with heavy metals.Through the study,the following results were obtained:(1)According to the total amount of seven heavy metals in the three media of water,sediment and soil,it is found that Cr and Pb in the water exceed the class III standard limit of the surface water environmental quality standard,Cu,Zn,Cd and Pb in the sediment exceed the local soil background value standard,while seven heavy metals in the soil all exceed the local soil background value standard,indicating that heavy metals cause the most severe pollution to the soil.(2)The average concentrations of Cu,Cd and As in the soil near smelter A exceeded the soil risk screening value,while only As in the soil near smelter B exceeded the soil risk screening value.The five heavy metals of Cu,Zn,Pb,Cd and As in the soil mainly come from the smelting of heavy metals,among which the concentration of Cu,Pb,Cd and As in the soil near the smelter A gradually decreases from the center to the surroundings.The heavy metals in the soil near smelter A are at the level of intense ecological hazard,while the heavy metals in the soil near smelter B are at the level of moderate ecological hazard.The Cd produced by the two smelters has the highest contribution rate to ecological hazards,and the ecological hazards to the surrounding soil are the most serious.(3)The seven heavy metals in the soil near the two smelters mainly exist in the form of residue state.In the effective state,the proportions of Cr,Ni,Cu and As oxidation states are the largest,while Zn,Cd and Pb are mainly in the reducing state.Only the leaching concentrations of Pb and As in the soil near smelter A exceeded international limits.The leaching concentrations of seven heavy metals were positively correlated with the exchangeable and reducible states.(4)According to the light-emitting bacteria method,it can be concluded that the biotoxicity of the three heavy metals is As>Pb>Cd,Cd and Pb in the soil of two smelters are at the level of micro toxicity biotoxicity,while As in the soil is at the level of heavy toxic biotoxicity.The action types of the three Cd-Pb,Pb-As and As-Cd binary heavy metals are synergistic,antagonistic and antagonistic respectively.The toxicity of binary mixed pollutants of three heavy metals can be accurately predicted by the biological toxicity of single Cd,Pb and As and the dose-adding model.The above results show that the closer the soil is to the smelter,the more serious the pollution will be caused by Cu,Pb,Cd and As.Therefore,the site selection of smelter and the utilization type of surrounding soil should be strictly controlled;Even if the content of single heavy metal is too high,it will cause strong ecological harm to the surrounding environment.Therefore,great attention should be paid to the large amount of Cd produced by the smelter;Although the content of As in the soil is not as high as Cd and Pb,but because of the greater biological toxicity of As,it will have a greater toxic effect on the surrounding organisms,so it can not only take the content of heavy metals in the environment as the only standard to evaluate the pollution level of heavy metals;The mixing of Cd and Pb will increase the toxic effect of heavy metals on organisms,which requires not only the pollution of single heavy metals but also the combined toxic effect of multiple heavy metals to be considered in the treatment of heavy metal pollution.