Research On The Ecological Risk Assessment Model Of Heavy Metal Pollution On The Farm Soil Near The Mine

The ecological risk assessment of soil pollution is a rapidly developing research field in recent years. In 2005, Weeks puts forward the "stacked" evaluation framework of the ecological risk about soil pollution. In 2007, based on the "stacked" evaluation framework, Critto and Semenzin put forward the expert decision support systems of the ecological risk assessment of environmental pollution, and thus the evaluation model is the hot spot in current environmental research. The author read a large number of domestic and foreign inspection about the environmental assessment of heavy metal pollution in soil and the bioavailability of heavy metal in soil. In this thesis, heavy metal forms extracted by seven kinds of single extractions(HCl,HOAC,CaCl2,NH4OAC,EDTA,NH4NO3和NaNO3) and two kinds of sequential extractions. Compare the absolutely bioavailable heavy metal in the sweet potato with the heavy metal forms by means of chemical extractions. Do the analyze of them, to found out the bioavailability of heavy metal in the soil, and try to find the best extraction for bioavailability of heavy metal.Based on the ecological risk features of heavy metal pollution in the soil of mine, the bioavailability of heavy metal in the soil, and entropy principle & proof weighted principle, this thesis puts forward the potential ecological risk assessment model:RI =(Er1×Er2×Er3…×Ern)1/n,Eri= Tri×Cfi . Cfi stands for the pollution index of effective fraction; Tri stands for the toxic response coefficient. Eri stands for the potential ecological risk index of element i. RI stands for the potential ecological risk index of heavy metals in the soil. To establish three kinds of evaluation models:(1) Bioavailability Evaluation Model Cibio—stands for the bioavailability fraction (mg/kg); Cio—stands for the calculation (mg/kg).(2)Sulfide Evaluation Model Ci硫—stands for the sulfide fraction (mg/kg)(3)Potential Bioavailability Evaluation Model Ci总—stands for the total heavy metal (mg/kg); Ci残—stands for the residues extracted by six sequential extraction (mg/kg);In the last, the author does the assessment on Tangjia mine in Hanyuan by Single Index, Nemerow Index, Geoaccumulation Index, Hakanson Index and The Potential Ecological Risk Assessment. Compare the ecological risk assessment data, the environmental assessment data of the total heavy metal with the absolutely bioavailable heavy metal in the sweet potato. Based on the analyze of them, the author finds out that the environmental assessment of the total heavy metal expands the extent of the pollution. The potential ecological risk assessment is more reliable than the environmental assessment of the total heavy metal.