Characteristics And Human Health Risk Aseessment Of Heavy Metals In Agricultural Soil-crops In Abandoned Lead-zinc Mining Area In Duyun City

In this paper,the soils and crops of the farmland in the abandoned lead-zinc mining area in Duyun city Guizhou province were studied.To investigate the pollution of 8 kinds of heavy metals in farmland soil in abandoned lead-zinc mining areas and the enrichment of 8 kinds of heavy metals in crops,two sampling sites were set up,and a total of 74 samples were collected.The soils samples were dissolved by HNO₃-HClO₄-HF method,and the crops were dissolved by HNO₃-H₂O₂ method.According Inductive Coupled Plasma Emission Spectrometer?Atomic Absorption Spectroscopy?Atomic fluorescence spectrometer to measure the total content of Cu,Zn,Ni,Hg,As,Cd,Pb and Cr in soils and crops samples.Based on the background value in Guizhou province and the national secondary standard for soils,Single factor index,Nemero Comprehensive index,Potential Ecological index and Pollution Load index methods were used to evaluate the pollution level and potential ecological risk of heavy metals in soils;Single factor index,Comprehensive Pollution index and Enrichment Coefficient were used to evaluate the crops.Using USPEA?EPA?human health risk assessment model to estimate the health risk for human body;Based on the content of heavy metal in crops,the effects of the crops on human health were evaluated by using hazard quotient.The result shows that:?1?According to the soil background value of Guizhou Province,Abandoned lead-zinc mine soil were exceeded standard rates of As,Cd,Cr,Cu,Hg,Ni,Pb,Zn were 46.15%?100.00%?13.46%?92.31%?100.00%?51.92%?100.00%?100%respectively;The soil in the abandoned lead-zinc mine area is between weakly acidic and weakly alkaline,with a pH value between 6.10-7.64and the average value of 6.99.The single-factor index method shows that all the soil in the mining area was polluted by 8 kinds of heavy metals,and the pollution degree is different;Pb,Cd and Zn of soil are all greater than 3,which all belong to the heavy pollution level.while sorted the array in a descending order Cd>Zn>Pb>Hg>Cu>Ni>As>Cr;?2?The soil environmental quality standard?grade 2,GB15618-1995?was adopted as the evaluation standard,The comprehensive pollution index study shows that the heavy metal pollution levels of 52 sampling points in the study area are different,and the comprehensive pollution index was greater than 3,all of which are heavy pollution.The potential ecological risk showed that RI of sample points of 9.61%is a strong ecological risk level between 600-1200,and RI of sample points of 90.39%is greater than 1200,indicating a strong ecological risk level.According to the pollution load index method 21%of the sampling was mild pollution levels,nearly half of the sampling was moderate pollution levels,and 28.8%was severe pollution levels.?3?The heavy metal content of crops indicated that the accumulation of 8heavy metals in different crops was different,and the average accumulation content was in the order of Zn>Cd>Cu>Pb>Ni>Cr>As>Hg.Based on the food safety limit value of crops and the comprehensive pollution index method results show that the comprehensive pollution index of 75%crops samples is greater than 3,which is a heavy pollution.The enrichment coefficient of crops indicated that the average enrichment coefficient of 8 heavy metals was Cd>Cu>Ni>Zn>As>Cr>Pb>Hg.?4?To evaluate the potential health risk of heavy metal pollution on the human body;with total amount of heavy metal for reference,risk index HI for adults and children was 0.61 and 3.75 respectively,adult potential non carcinogenic risk can be ignored,the potential total of the risk of cancer in children was greater;The TCR values of adults and children are 2.3×10-3 and3.51×10^-3 respectively,exceeding the risk threshold range?10-6¹0-4?.Soil heavy metal elements may cause potential carcinogenic risk for adults and children.In summary,the soil around the abandoned mining area is seriously polluted by heavy metal on the whole,which should be paid attention to by relevant departments.the soil needs to be restored and managed urgently.As far as the types of crops cultivated in the mining area was concerned,in case of over a long period of time was used for food in the mining area will have an impact on human health;The species selection and safety of crop varieties need further study.