Risk Assessment And Leaching Extraction Of Antimony(Sb) And Arsenic(As) Contaminated Soils

Antimony?Sb?and arsenic?As?are global pollutants.Due to the disordered mining and smelting activities,a large amount of smelting residues of Sb and As enter the soil environment,which threatens the ecological environment and human health seriously.In recent years,more and more attention has been paid to the study of the fraction,toxicity and phytoxicity of heavy metals in soil.China has the largest Sb deposits and has been considered as the major Sb production country of the world.In this study,contaminated soils of Sb and As were collected and leached with different extractants.The physicochemical properties,fractionation and microbial diversity of Sb and As in three soils before and after leaching were analyzed,and the characteristics of Sb and As contamination were discussed.Combined with toxicity assessment and pot experiment,the risk assessment of leached soil was discussed,and the following were the conclusions in the experiment:?1?The soil pollution of Sb and As in this mining area were seriously.The average Sb concentrations in paddy soil?L?,upland soil?M?and waste ore soil?H?were 145 mg kg^-1,720 mg kg^-1 and 6876 mg kg^-1,repectively,while the average As concentrations in L,M and H were found as 18.2 mg kg^-1,103 mg kg^-1 and 380 mg kg^-1,respectively.In the soil of this mining area,Sb and As in the three soils were both bioavailable according to SBET.From the analysis of the dominant bacteria in soil,Firmicutes,Euryarchaeota and Chlamydaie and Acidobacteria can be observed as the best resistance bacteria to Sb and other heavy metals in this study area.?2?In the three types of soils,NaH₂PO₄,citric acid?CA?and tataric acid?TA?have better removal effect on Sb than?NH₄?₂C₂O₄.However,the removal effect of NaH₂PO₄ and CA on As were much better than?NH₄?₂C₂O₄ and TA.CA has the least impact on soil physiochemical properties among the four extractants.The fractions in three types of soils were redistributed after leaching with different extractants.?NH₄?₂C₂O₄ increased the F1 and F2 of Sb and As in the soil and CA reduced the F8of Sb and As in the soil.According to the observation of microbial diversity in soil before and after leaching,TA caused a significant decrease on microbial diversity in the three soils.?3?The toxicity risk assessment experiment shows that TA can increase the leachability,and the mobility and bioavailability of Sb and As were increased by the leaching of four extractants,indicating that the toxicity of Sb and As were easier to be absorbed by organisms after leaching.Similarly,in the veletable planting experiment,the leaching of?NH₄?₂C₂O₄ and TA promoted the absorption of Sb in vegetables,while CA amd?NH₄?₂C₂O₄ can increase the absorption of As in vegetables.The analysis of HQ and CR index showed than Sb had adverse effect on adults and children,and it will cause health risk assessment at moderately or highly of As polluted soils,indicating that long-term consumption of such vegetables has a certain risk of cancer.