Distribution Characteristics And Control Countermeasures Of Heavy Metals In Agricultural Soil Of Zunhua Area

Agricultural land is an important place for agricultural and animal husbandry production,and healthy agricultural land soil is an important basis for ensuring the quality and safety of agricultural products.The prevention and control of soil pollution is more related to people’s safety in eating and living.Zunhua city has a long history of mining development,which is located in the northwest of Tangshan.The large-scale development of mineral resources has made great contributions to the economic and social development,but also has different impact on its ecological environment,especially the soil environment.It is necessary to study the soil pollution status of agricultural land in Zunhua City in order to master the charactors of soil pollution and its influencing factors.The soil environment quality of Zunhua city is generally good.The results of mathematical statistics show that the exceedance rate of four heavy metals except As is exceeds 60%,according to the natural background value of soil in Hebei Province.Cd,Hg,As and Pb elements are not over standard,except for 8%Cr,according to risk control standard of soil pollution in agricultural land which is published in 2018.There are some risks in soil environment.The main pollution elements of the evaluation of the ground accumulation index are Cd,Cr,and the potential ecological evaluation is Hg and Cd.The main reason is that Hg has high toxicity coefficient and high ecological risk;while Cr content is high,and the evaluation level of ground accumulation index is high.The proportion of light pollution in the evaluation results of Cd and Cr elements’ground accumulation index accounts for more than half.The results of the assessment of potential ecological risk index of heavy metals are Hg and Cd.The composite ecological risk assessment results show that the area of light ecological risk is the largest,and the strong risk plot is distributed in the middle of Shahe basin and the west of other small basins.The middle risk area is attached to the surrounding of the strong risk area,and the northern part of the river basin is also medium risk.Correlation analysis shows that As and Cr sources have strong correlation,Pb Hg and Cd may have homology;As Cr and Pb Hg Cd are not homologous.Spatial variation analysis shows that Cd Hg and CR have strong autocorrelation,and the heavy metal content at sample points is affected by large-scale regionalization factors,and As element correlation is weak.The heavy metal content of all soils in the garden and landform hills is higher than the average value,and the heavy metal content of each soil within 500m from the mine and traffic trunk line is higher than the average value,indicating that the land use type,landform and distance from the mine and traffic trunk line have an impact on the content of heavy metals in the soil.The heavy metal content of soil is related to natural source mainly composed of As and Cr,and the pollution sources of man-made activities in industrial mining and transportation(Cd,Hg,Pb)of iron ore and dolomite.According to the situation of soil heavy metal pollution,pollution risk,spatial variation and influencing factors,Zunhua city is divided into three types:mine ecosystem restoration and treatment area,farmland comprehensive treatment area and natural reserving area.The paper puts forward the restoration strategy which is mainly natural restoration and artificial induction as auxiliary.