Study On The Migration Of Heavy Metals In Soil-Plant-Groundwater System In Donglai, Inner Mongolia

Human production practices may lead to an increase of heavy metal content in the environment,and endanger the ecological environment,when the content of heavy metal is beyond the normal range.By field sample collection and indoor experiment data processing analysis,the distribution characteristics,migration and transformation law of seven heavy metal elements of quaternary soil-plant-groundwater system is analyzed,in the 100km~2 area around Donglai town of Tongliao city of the Xiliao River Plain.It can supply reference to the prevention and controlment of heavy metal pollution.The quaternary soil component of the research zone is mainly of clay,sub-clay and sandy soil,and the average content of heavy metal elements Zn,Cr,Cu,Pb,As,Cd and Hg in the surface soil is:64.397 mg/kg,55.267 mg/kg,22.407 mg/kg,19.73 mg/kg,7.797 mg/kg,0.131 mg/kg,0.015mg/kg,which is polluted by a certain heavy metal,and the pollution of Cd is the most serious.With the increase of soil depth,the content of each element decreases gradually and tends to be stable.Due to the strong adsorption of clay and sub-clay layer,the content of heavy metal elements increased significantly in the depth of 121-170cm,even higher than that in the surface soil.As a plant sample the average content of Zn,Cu,Pb,Cr,As,Cd and Hg in corns are:13.623 mg/kg,1.24 mg/kg,0.33 mg/kg,0.282 mg/kg,0.052 mg/kg,0.013mg/kg and 0.002mg/kg.Except that the content of Pb is 1.65 times of the limit value of the food safety,the content of the remaining elements is not exceeded,so the corns are polluted by Pb.Groundwater is not contaminated for that there are very few heavy metals and the majority of groundwater is in line with the II standard of groundwater quality.Heavy metals in the study area are mainly derived from the use of pesticides and fertilizers.In the process of soil,plant and groundwater migration,the soil is polluted by Cd,and the plants are polluted by Pb,while the groundwater is not polluted.The content of heavy metals in the soil-plant-groundwater system in the study area conforms to the following rules:soil>plant>groundwater.The existence of the difference between the three pollution conditions indicates that the concentration of heavy metal in soil,plant and groundwater is related to its physical and chemical properties.From the perspective of ecological protection,plants have fixed heavy metals and have a protective effect on the ecology.The existence of thick layer of gas belt significantly reduces the migration ability of heavy metal elements in groundwater,which is beneficial to protect groundwater from heavy metal pollution.