广西黎塘岩溶区富含铁锰结核土元素迁移特征

【目的】研究广西黎塘岩溶区土壤富含铁锰结核背景下元素含量与迁移特征,为富含铁锰结核土的有效修复提供理论依据。【方法】选择具有代表性的未受农业耕作影响的富含铁锰结核土为试验样地,其成土母岩为碳酸盐岩,以成土母岩为碎屑岩的土壤为对照,分层采集剖面A(0~35 cm)、B层(35 cm)土壤及对应岩石样品,测定土壤、岩石氧化物及重金属元素含量。【结果】广西黎塘岩溶区土壤主要是Si、Al和Fe的氧化物,三者之和在土壤剖面A、B层的平均含量分别占总量的86.32%和86.30%;广西黎塘岩溶区土壤的SiO_2和Fe_2O_3含量均低于对照,而Al_2O_3、Ca O和Mg O含量高于对照。广西黎塘岩溶区土壤Cd、Pb和Zn含量顺序为ZnPbCd,其中剖面A层Cd和Pb平均含量均超过B层,而Zn平均含量低于B层,剖面A、B层Cd、Pb和Zn平均含量均已超过广西土壤元素背景值及成土母岩为碎屑岩的土壤,未超过土壤环境质量二级标准值。广西黎塘岩溶区土壤以高硅铝系数、低盐基总量淋溶系数为特征,土壤剖面B层风化淋溶强度高于A层,风化淋溶程度整体上高于碎屑岩成土。土壤烧失量(LOI)与SiO_2含量、Al_2O_3含量、硅铝率、盐基总量淋溶系数的相关系数分别为-0.8063、0.7091、-0.8570和-0.2923,土壤剖面A、B层Ca、Mg元素及B层的Cd元素发生了亏损,其他元素均表现为富集或强烈富集。【结论】成土母岩为碳酸盐岩的土壤氧化物、重金属含量、风化淋溶强度、迁移特征等与成土母岩为碎屑岩的土壤具有差异,铁锰结核的存在已造成重金属元素在土壤中的积累并具有潜在污染。

Transferring features of elements in soil rich in iron-manganese nodules karst area of Litang,Guangxi

Objective] Element contents and transferring features of soil rich in iron-manganese (Fe-Mn) nodules in karst area in Litang,Guangxi were studied in order to provide theoretical basis for effective remediation of soil rich in Fe-Mn nodules.Method] The representative soil rich in Fe-Mn nodules which was not affected by agricultural cultivation were selected as sample plots.Its soil mother rock was carbonate,control was soil whose soil mother rock was clastic rock.Stratified sampling profiles layers A (0-35 cm),B(＞35 cm) soil,and corresponding rock samples were obtained.Then,the oxides contents and heavy metal of soil and rock were determined.Result] The soils in the karst area in Litang were mainly oxides of Si,Al and Fe.The average content of three oxides in the soil profile layers A and B accounted for 86.32％ and 86.30％ of the total respectively.The contents of SiO2 and Fe2O3 were lower than control,while the contents of Al2O3、CaO、MgO were higher than control.The contents order of Cd、Pb、Zn in the karst area in Litang was Zn＞Pb＞Cd,the average contents of Pb and Cd in layer A were higher than layer B,while the contents of Zn were the opposite.The average contents ofZn,Pb and Cd in profile layers A and B were all over Guangxi soil element background value and soil whose soil mother rock was clastic rock,but they did not exceed environmental quality standard(Ⅱ) for soils.The soil in the area contaIned high silicon-aluminum coefficient and low eluviation coefficient of total base.The weathering and leaching intensity of layer B in soil profile was higher than that in layer A,the degree of weathering and leaching of soil was higher than that of clastic soil.The correlation coefficient were-0.8063,0.7091,-0.8570,-0,2923 respectively between soil ignition loss (LOI) and SiO2 content,Al2O3 content,silicon-aluminum coefficient and eluviation coefficient of total base.The elements Ca and Mg in layers A and B and Cd in layer B were loss,while others presented enrichment or strong enrichment.Conclusion] The oxides,heavy metals,intensity of weathering leaching,transferring features are different in soils from carbonate rocks and clastic rocks.The heavy metals have been accumulated by Fe-Mn nodules and posed potential pollution on soil.