Research On Health Risk Assessment And Safe Utilization Technology Of Cultivated Land With High Heavy Metal Content In Northwest Guizho

A series of food security problems caused by the accumulation of heavy metals in arable soils leading to excessive heavy metal content in crops in recent years cannot be ignored.The northwestern part of Guizhou Province is a typical area with high geological background of heavy metals.Previous studies have demonstrated that soil heavy metals in karst areas are low active and the accumulation of heavy metals varies significantly among crop varieties,and these reasons can lead to over protection or under-protection of soil.In this paper,we systematically evaluated the health exposure risk of heavy metals in regional soils and crops by testing the contents of heavy metals Cd,Hg,As,Pb and Cr in soil-crop synergy samples in the study area,and inferred the baseline values of environmental risks in regional cropland soils based on the species sensitive distribution model（SSD）.In addition,the effects on heavy metal Cd in different crops were explored by treating the study area with different fertilizers（biochar,cow manure+phosphate solubilizer,peat soil+phosphate solubilizer,calcium-magnesium phosphate fertilizer+phosphate solubilizer and rapeseed cake fertilizer+phosphate solubilizer）,conditioners（soil conditioner A,soil conditioner B,lime,intaglio,seafoam,montmorillonite,diatomaceous earth and calcium-based bentonite）and foliar deterrents,and the crops seed Cd low accumulation maize and rice were screened by cluster analysis and Pareto analysis methods.The main findings were as follows.（1）According to the preliminary research survey of the whole Northwest part of Guizhou Province Shuicheng District（Study Area 1）,it was found that both maize and rice soils in this area showed high levels of heavy metals and both were higher than the soil background in Guizhou,and maize soils were contaminated with heavy metals to a higher extent than rice fields.In contrast to the high levels of soil heavy metals,only 3.51%and 0.88%ofω（total-Cd）andω（total-Pb）in maize seeds exceeded the national food safety limits,and 13.04%and 4.35%ofω（total-Cd）andω（total-Cr）in rice exceeded the limits.The carcinogenic/non-carcinogenic risks of heavy metals for both adults and children in the study area were at low levels.The derived environmental benchmark values for Cd,As,Pb and Cr in the study area were0.67,771.99,40.85 and 609.88 mg·kg^-1for maize soils and 2.42,8.88,41.41 and27.84 mg·kg^-1for paddy soils,respectively,using the species sensitivity distribution curve method in study area 1.The derived HC₅values for heavy metals in maize and rice soils are higher than the soil risk screening values in the current standards to varying degrees,and the HC₉₅values are higher than the soil risk control values,and the current soil standards are strict for the evaluation of the region.（2）According to the investigation of"Shuangshui+Miluo"（study area 2）in The northwestern part of Guizhou Province,different fertilization methods had different degrees of influence onω（total-Cd）in different crops,and the five fertilization treatments had the best effect on maize and rice crops.Theω（total-Cd）in different crops varied among soil conditioner treatments,with lowerω（total-Cd）in rice and maize and higherω（total-Cd）in potato and rice.The vast majority ofω（total-Cd）in potatoes did not exceed the national standard values,whileω（total-Cd）in both maize and rice crops did not exceed the national standard values,andω（total-Cd）in pepper crops did.The results of the foliar deterrent test revealed thatω（total-Cd）in all vegetable species except lotus white was reduced to varying degrees under the spray treatment.The averageω（total-Cd）size of soil heavy metals of maize and rice in study area 2 showed high levels of water soil heavy metals were ranked as:rice>maize.In contrast to the high level of soil heavy metals,only 5.7%of maize seeds and rice hadω（total-Cd）exceeding the national food safety limit,and the averageω（total-Cd）size of crop heavy metals was ranked as:rice>maize.The five maize varieties with low Cd accumulation screened by cluster analysis with Pareto analysis in study area 2 were JHY809,JDY808,AD778,SN3H and SY13;the five rice varieties with low Cd accumulation screened were DMY6188,GY725,NY6368,SY451 and DX4103.these varieties can be used as karst These varieties can be used as suitable maize and rice varieties in areas with high Cd content and promoted for cultivation.In addition,the results of species sensitivity curve analysis showed that the Cd thresholds of maize and rice in the study area ranged from 0.30～10.05 mg·kg^-1and 0.89～24.39 mg·kg^-1,respectively,indicating that 5%to 95%of the crop species within the protected cropland were not contaminated by heavy metal Cd in the cropland soil.