贵州晴隆锑矿区土壤中锑的形态分布和地球化学模型

Species distribution and geochemical modeling of antimony in the Qinlong antimony mining area

以贵州晴隆锑矿区某冶炼厂及周边地区土壤为对象研究了锑的形态分布特征.结果发现,冶炼厂土壤中锑污染严重,含量最高达31265 mg·kg^(-1),但在下游土壤中随距离增加,锑浓度迅速下降到100mg·kg^(-1)以内.XRD和XPS结果显示土壤中主要含锑化合物为锑酸钙(Ca_(2)Sb_(2)O_(7))、锑酸钾(K_(3)Sb_(5)O_(14))以及氧化锑(Sb_(2)O_(5)),锑以五价形态存在.连续提取形态分析表明除残渣态外,厂区附近污染土壤中碳酸盐和金属氧化物的共沉淀态是锑的主要宿主相,而下游土壤中吸附态比例显著升高,说明在迁移过程中土壤中锑的活性增加.构建了以水合铁氧化物和针铁矿作为锑主要活性表面的土壤中锑地球化学多表面形态模型(MSM),当采用1 mol·L^(-1)Na_(2)HPO_(4)提取的锑作为总有效态锑输入值时,该模型可很好地预测不同性质和污染程度的土壤中锑的溶出效应(RMSE=0.29),说明该模型可为准确评估锑冶炼厂周边污染土壤中锑生态毒性和迁移淋溶风险提供有潜力的工具和方法.

The speciation of antimony(Sb)in the soils of a smelter and the surrounding areas in the antimony mining area of Qinglong,Guizhou Province was investigated.It was found that the smelter soils were severely contaminated by Sb,with the highest content reaching 31265 mg·kg^(-1),while the Sb contents in the downstream soil decreased rapidly to less than 100 mg·kg^(-1)with increasing distance.The main Sb-bearing compounds were identified by XRD and XPS to be pentavalent calcium antimonate(Ca_(2)Sb_(2)O_(7)),potassium antimonate(K_(3)Sb_(5)O_(14))and antimony oxide(Sb_(2)O_(5)).Sequential extraction experiments showed that besides the residue fraction,the co-precipitation with carbonate and ferric oxides was the main species of Sb in soils at the smelter area,while the strongly adsorbed fractions were significantly higher in the downstream soils,indicating that the Sb mobility increased in the transport process.A geochemical multi-surface speciation model(MSM)for Sb in soil was developed with HFO and goethite as the main active surfaces.When Sb extracted with 1 mol·L^(-1)Na_(2)HPO_(4)was used as the total available Sb in the model,the model could successfully predict the dissolved Sb in soils with different properties and contamination levels(RMSE=0.29),indicating that the model offers a promising tool for assessing the ecological and leaching risks of Sb in contaminated soils around Sb smelters.