Studies On Pollution Characteristics And Risk Assessment Of Heavy Metal In Hebei’s Farmland Soil

Heavy metal pollution is a hot spot in farmland pollution research,and the impacts of heavy metal pollution to soil environment quality,crop production and quality are widely concerned.At present,the study of heavy metal pollution in farmland soils in China mainly focuses on the current situation and remediation,and the study on pollution characteristics are not clear enough.At the same time,the risk assessment methods and the evaluation indicator of heavy metal pollution in farmland soils in China are not developed well,because it is easy to appear the phenomenon that the evaluation results of soil and plant are inconsistent.Therefore,combined with the research project,this paper takes Hebei province as an example to define the present situation,causes and accumulation characteristics of soil Cd and Ni pollution.On the basis of risk assessment method of heavy metal pollution in farmland soil,combined with the reality of the new demand,put forward a set of risk assessment methods which comprehensively consider soil and plant pollution and pollutant accumulation.In order to provide scientific basis and technical support for farmland heavy metal risk control and remediation.The results are as follows:1.Defined the main elements,distributions and sources of heavy metal pollution in farmland soil in Hebei.In Hebei province,the content of heavy metals in farmland soil is generally low,and most of them can meet the safety of crop production.In the view of the area of heavy metal pollution,Ni and Cd are the two main pollution elements in soil,pollution area accounted for the total land area of Hebei Province in 0.61%and 0.53%respectively,and it significantly more than the other heavy metals.From the distribution of heavy metal pollution,Ni and Cd pollution of soil is mainly distributed in Tangshan,Qin Huangdao,Baoding,Shi Jiazhuang.Factor analysis showed that mining,industrial activities and sewage irrigation were the main sources of Cd,while Ni was mainly affected by mining.2.Defined the contribution rate of exogenous inputs to heavy metals pollution.The contribution of different input sources to the input of cadmium and nickel in Farmland Soils in Hebei was different.Atmospheric deposition(80.51%)had the largest contribution to Cd input,followed by irrigation(8.70%),while livestock manure(6.30%)and fertilizer(4.49%)contributed relatively low.In terms of Ni input,atmospheric deposition(64.90%)and livestock manure(25.73%)were the main contributors,followed by fertilizer(6.86%),and the contribution of irrigation(2.50%)was relatively low.Based on the analysis of input and output of Cd and Ni in farmland soil,the net input of Cd and Ni in Hebei soils was 10.4 g/hm~2/yr and 106 g/hm~2/yr respectively.And the average annual cumulative rates were0.00462 mg/kg/yr and 0.0472 mg/kg/yr.3.A set of risk assessment methods has been comprehensively developed.Soil-plant-trend three evaluation methods on the limitations of the methods of risk assessment for farmland soil polluted by heavy metals considering the input and output of heavy metals and the accumulation characteristics of heavy metals in soil.The main pollution input is defined,and the source of pollution is effectively controlled,which provides a theoretical basis for the development of efficient and targeted repair strategies.4.Validated the scientific and practical of new risk assessment method.The soil Cd and Ni pollution in Zhao county,Zhao Han village,Gaoyi and Beiqing village were evaluated by three different evaluation methods,and the new assessment method shows its advantages.The evaluation results of the new method showed that,except for the Beiqing village had low Cd pollution risk,there was no real risk of Cd and Ni in other research areas,but there was a certain degree of low potential risks.At this stage,the focus of soil pollution prevention and control in these areas should strengthen the source control and maintain or reduce the net input of farmland Cd.