栾川矿集区钼矿尾渣与土壤中钼的迁移转化机理

Mechanism of Molybdenum Migration and Transformation in the Tailings and Soils in the Luanchuan Mining Area

为提供栾川矿集区所在流域下游水源地陆浑水库Mo污染的源头控制依据,开展了6座钼矿尾矿库尾渣和土壤的野外调查及三道庄尾矿库尾渣和土壤的Mo赋存形态分析和降雨淋滤试验,以探讨Mo在钼矿尾渣与土壤中的迁移转化机理。结果显示,尾矿库尾渣Mo平均含量为238.24 mg/kg,浸出液Mo含量达0.26 mg/L;土壤Mo平均含量为125.88 mg/kg;尾渣残渣态Mo占比97.71%,土壤残渣态Mo占比63.66%,可交换态和碳酸盐结合态分别占比22.35%和11.80%。酸-偏碱性降雨淋滤后,尾渣中残渣态Mo占比不同程度减少,中-偏碱性降雨更利于尾渣残渣态Mo向碳酸盐结合态转化,使之由淋滤前的1.19%分别增加到18.85%和24.14%,提高了尾渣中Mo的迁移性。酸性降雨时土壤铁锰氧化态和有机态Mo占比大幅度升高,其他形态Mo占比均一定幅度降低;中性-偏碱性降雨时土壤残渣态和有机态Mo占比升高,碳酸盐结合态和铁锰氧化态大幅度降低,表示酸性降雨可促进土壤中形成铁锰等钼酸盐,而中-偏碱性降雨可能有利于土壤中形成铁锰等氢氧化物和碳酸盐,阻碍了铁锰等钼酸盐的产生,一定程度上提高了Mo的迁移性。因尾渣和土壤矿物组成和理化性质不同,降雨淋滤下Mo在两者中的迁移转化机理存在一定差异,但总体而言,酸-偏碱性降雨均可促进Mo的迁移转化,从而影响水土环境。

To investigate the controls of the molybdenum(Mo)pollution sources in the Luhun Reservoir,we conducted a field survey with collecting six Mo tailing ponds.Molybdenum speciation analysis and leaching experiments were performed to study the mechanism of Mo migration and transformation in the tailings and soils.The average Mo content in the six samples of tailings and soils are 238.24 and 125.88 mg/kg,respectively,and the Mo content in the leached solution is 0.26 mg/L.Tessier extracting result shows that the Mo residual in the tailing was 97.71%,while together with that,the exchangeable and carbonate bound Mo in the soil are 63.66%,22.35%,and 11.80%,respectively.After the leaching experiments with acid to alkaline rainfalls,the Mo residual in the tailing decreased.The neutral and alkaline rainfall favor the transformation of Mo residual to carbonate Mo bound,leading to the carbonate Mo bound increasing from 1.19%to 18.85%,and then to 24.14%.This indicates that the neutral and alkaline rainfall can enhance the transporting capability of Mo.In the soils,the iron-manganese oxidation state and the organic Mo bound increased largely,and all the other Mo species decreased by different degree with the acid rainfall leaching.The residual and the organic Mo bound increased and the carbonate Mo bound and the iron-manganese oxidation state decreased largely with the lea-ching of neutral-alkaline rainfall.It suggested that the acid rainfall can increase the formation of the molybdate of iron and manganese,while the neutral and alkaline rainfall likely favor the formation of the iron and manganese hydroxide and carbonate,which prevents the formation of the iron and manganese molybdate,enhancing the transporting capability of Mo by an order of magnitude.Although the differences of the ore and the physicochemical properties of the tailings and the soils can cause different Mo transportation and transformation,the acid to alkaline rainfall can enhance the transportation and transformation of Mo in the two media,and hence affect the soil and aqueous environments.