Distribution Characteristics And Health Risk Assessment Of Heavy Metals In Reconstituted Soils And Crops From Sulfur Mine Wasteland

The reclamation and utilization of mining wasteland is of great significance to improve the ecological environment,broaden the land use space and adhere to the red line of 1.8 billion mu cultivated land.There are many scientific and practical problems such as the current wasteland reclamation attach importance to engineering and light ecological restoration,the obvious increase trend of heavy metal content in the reconstituted soil,the unclear migration law of heavy metal in the reconstructing soil-crop system of the mining wasteland and so on.In view of these problems,the southwest area of a sulfur mining wasteland reclamation area was used as the research object,the reconstructed soil as the core of research is taken.Based on soil and crop"point-to-point" sampling and laboratory test analysis,the content distribution characteristics of five heavy metals(Cd,Cr,Ni,As,and Hg)in reclaimed surface soil and crop(corn)were systematically analyzed by using the classical statistical method and geostatistics theory.The health risk assessment model of soil-crop system was established,based on the model,combined with pollution index methods,the pollution status of heavy metals of the soil-crop system in the reclamation area were explored,and the priority control elements in the reclamation area were determined,the corresponding control measures were proposed.In addition,the vertical change trend of five heavy metals was analyzed,and the changes of Cd morphology under different physicochemical properties were discussed.The main results are as follows:(1)Except for Hg,the other four heavy metals exceeded the standard in the reclaimed surface soil,of which the Cd exceeded the standard rate of 90%,and the mean value of the five heavy metals in the corresponding corn kernels did not exceed the limit of National Standards for Food Hygiene.Inverse Distance Weighting spatial interpolation showed that the spatial distribution patterns of heavy metals were different.The evaluation results of the heavy metals in the soil and crop from the reclamation area indicate that the heavy metals in the top soil are seriously polluted,and Cd is the main pollution factor,while the heavy metals in the corn kernels belonged to the safety level on the whole,and the bioconcentration coefficients are low(BCF<0.1).The correlation analysis of heavy metal content between soil and corn showed that the soil has a direct impact on corn and it is a spatially non-stationary relationship.(2)The average content of five heavy metals in the reclaimed profile soil is not obvious with the vertical depth.Scanning electron microscopy-electron diffraction spectroscopy(SEM-EDS)in different soil depths was used to analyze the occurrence of Cd under different soil thicknesses.Isomorphs of Cd element were observed,and the proportion of Cd reducible state is the highest.The total amount of heavy metals is the most important factor affecting the distribution of Cd forms,followed by pH,organic matter,and CEC.(3)The results of health risk assessment of heavy metals in reclaimed area showed that a single heavy metal in soil-crop system would not cause non-cancer risk and cancer risk to human body under four routes of exposure of in study area for adults and children,but the pollution of compound heavy metals might cause harm.Cr is the most important element that leads to the carcinogenic risk of local residents in the soil-crop system.The comprehensive control value of Cr in adults and children is less than 0.5 mg·kg-1.Thus,Cr is the priority control object,followed by Cd,Ni and As.Different remediation measures are taken for different heavy metal risk control.Figure[19]table[18]reference[128]...