Heavy Metal Pollution Characteristics And Antimony Control Of Farmland Soil In Typical Antimony Mining Area

Antimony is a highly toxic global pollutant.Due to the disorderly mining of mining areas and the random discharge of antimony-containing waste gas,waste residue and waste water,the content of Sb in the environment is increasing,which seriously threatens the ecological environment and human health.In recent years,more and more researchers have paid attention to the influence of mining on the surrounding area and watershed.As a large country with antimony reserves and production,the influence of antimony mining on the surrounding area and river basin should be paid attention to.In this paper,three typical antimony ore areas（Lengshuijiang mining area,Nandan mining area,Xunyang mining area）were selected as the research objects,and the heavy metal pollution status and ecological risk of farmland soil around the antimony ore area and watershed were analyzed,providing theoretical basis for the remediation and safe utilization of farmland pollution around the antimony ore area and watershed.On this basis,sepiolite was modified with iron and manganese,and its remediation effect on Sb contaminated soil was analyzed.The following conclusions are drawn:1)The farmland soils around And in the drainage area of Longshuijiang were contaminated by As,Cd,Zn and Sb,and their concentrations were 2.26,14.07,1.77 and 53.54 times of the national limit standard,respectively.The potential risk index was 852.12,indicating that the soil was severely polluted and at a high ecological risk level.The majority of Sb is crystal Fe-Al,residual,amorphous Fe-O and amorphous Fe-Al,which are 29.97%,26.82%and24.80%,respectively.Nandan Chashan antimony mine surrounding and watershed farmland soil by As,Cd,Cu,Pb,Sb,Zn pollution,the concentration is 101.91,52.17,1.90,2.70,77.48,8.93 times of the national limit standard,potential risk index As high As 3240.52,is a severe pollution of soil,at a very high ecological risk level.Sb mainly consists of amorphous iron oxide,amorphous Fe-Al and crystalline Fe-Al,accounting for 36.52%and 32.64%respectively.The farmland soil around xunyang Antimony mine and watershed is mainly polluted by Sb,and its concentration is 15.2 times of the national limit standard.The potential ecological risk index is 175.58,belonging to the moderately polluted soil,at the level of moderate ecological risk.Sb mainly consists of amorphous iron oxide,amorphous Fe-Al state,crystalline Fe-Al state and residual state,accounting for 26.60%,26.22%and5.89%,respectively.The three mining areas are centered on smelters and tailings mining areas.Within the same radius,the heavy metal pollution degree of farmland soil around the mining area and downstream is more serious than that of the upstream,and the pollution degree is aggravated at the intersection of rivers.However,with the extension of the basin,the pollution degree gradually decreases,but still far exceeds the national limit standard.It can be seen that there are high potential ecological risks in the farmland soils around the three mining areas and in the watershed.2)Sepiolite modified by Fe and Mn has a porous structure,its specific surface area increases from 153.97 cm·g^-1to 181.86 cm·g^-1,the contents of Fe and Mn increased obviously and its adsorption performance is significantly improved.Compared with natural sepiolite,the adsorption efficiency of modified sepiolite is increased by 39%and the adsorption capacity is increased by about 12 times.XRD and FRIT spectra show that no ferromanganese crystals are found in the modified sepiolite,but there is a peak of ferromanganese oxides at1503 cm-1,which indicates that ferromanganese exist in amorphous form.Compared with its research performance,natural sepiolite reaches adsorption equilibrium at 2.5h,and its adsorption effect is best at the initial pH value of 9.At the same time,the adsorption effect of antimony increases with the increase of the initial concentration.In conclusion,the adsorption performance of modified sepiolite has been significantly improved.3)Compared with CK,all treatments could improve soil pH and organic matter contents,and sepiolite modified by 2.5%fe and Mn had the most significant effect.Compared with CK,the treatment can increase the soil type microtek hercynite combination state Sb（F4）,sulfide and the organic combination state Sb（F5）and the content of residue state Sb（F6）,reduce soil not obligate adsorption state Sb（F1）and obligate adsorption state Sb（F2）,amorphous iron oxides and amorphous iron and aluminum combination state the content of Sb（F3）,The content of Sb in different parts of pakchoi was decreased.Sepiolite modified by2.5%ferromanganese has the best effect on Sb reduction.Compared with natural sepiolite,the effect of Fe-Mn modified sepiolite was better at the same amount,and the Sb content of the whole plant decreased by about 30.25%.Compared with natural sepiolite,the contents of non-obligate adsorbed Sb（F1）and obligate adsorbed Sb（F2）in FM-Sepiolite soil were reduced by 1.7%and 6.64%,respectively,and the contents of Sb in root and leaf of Pakchoy cabbage were reduced by 12.56%and 28.81%,respectively.