Ecological Risk Assessment Of Heavy Metals In Farmland Soil In Certain Area In Anhui

With the implementation of China's Agricultural Land Soil Pollution Risk Control Standards GB15618-2018,farmland soil pollution management and control,especially heavy metal pollution risk management and control,and ensuring the safety of agricultural products has become the guiding ideology of farmland soil environmental management in China.At present,most of the evaluation of heavy metal pollution in farmland soil is mainly based on the content of heavy metal in the soil,and the quality and safety goals of the corresponding crops are not taken into account.Therefore,it is of great theoretical and practical significance to take into account the soil content and crop quality and safety goals,and to propose an evaluation method that is consistent with current farmland soil environmental management.In this study,rice,rapeseed and their corresponding root soils in an area in central Anhui were taken as the research objects.The contents and enrichment characteristics of Pb,Hg,Cr,Cd,As in soil and crops were studied,and the physical and chemical properties of soil and heavy metals in crops were analyzed.Correlation between soil physical and chemical properties and crop heavy metal absorption coefficient was analyzed.H???kanson potential ecological risk assessment method was modified based on pollutant type,pollutant type-crop heavy metal absorption coefficient,respectively.Modified H???kanson method,pollution load index method,geo-accumulation index method,Influence index of comprehensive quality were used to evaluate the ecological risk of heavy metal pollution in soil.The main results in this study are as follows:?1?The Pb and Cd of few points in paddy soil and rape soil exceed the soil risk screening value,but both are lower than the soil pollution control value.The Hg and Cd in paddy soil in a few points exceeded the national standard of crop,and all heavy metals in rape soil were lower than the standard.?2?The average ranking of heavy metal absorption coefficients of rice and rapeseedabsorption capacity of Hg and Cd between the two crops.High OM concentration inhibits rice from absorbing Hg,high p H and high CEC value inhibit rice from absorbing As,high p H value inhibits rice from absorbing Cd,and high CEC value inhibits rapeseed from absorbing As.?3?Based on the aim of rice safety and conservative principles,the modified H???kanson method based on pollutant type can accurately evaluate the ecological risks of As,Cr,Pb,and Cd in paddy soil,and overestimated the ecological risk of Hg;the modified H???kanson method based on pollutant type-absorption coefficient can accurately evaluate the ecological risks of As,Cr,Pb,Hg ecological risk,overestimation of Cd ecological risk.Both improved H???kanson methods can accurately assess the ecological risks of Pb and As in rape soil,but overestimate the ecological risks of Cd.?4?The evaluation results of the soil-crop Influence index of comprehensive quality showed that the comprehensive quality of the soil-rice system and the soil-rape system are mainly grade I and grade II,and the pollution risk is low;the soil-crop system pollution is mainly related to soil pollution especially to Cd and Pb.?5?Taking into consideration the soil content and the quality and safety goals of crops,it is recommended to combine the modified H???kanson method based on pollutant types and modified H???kanson method based on pollutant type-absorption coefficient for heavy metal pollution risk assessment of paddy soil;combine the I_geo method and modified H???kanson method for rapeseed soil ecological risk assessment of heavy metal pollution.