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.