Characteristics of transfer and their influencing factors of heavy metals in soil-crop system of peri-urban agricultural soils of Nanning, South China

A total of 150 pairs of concentrations of Hg、Cd、Cr、Cu、Ni、Pb and Zn in the soils、grains of rice、vegetable and corn were determined in peri-urban agricultural soils of Nanning.The results indicated the mean soil concentrations of Hg、Cd、Cr、Cu、Ni、Pb and Zn were 0.116、0.202、56.76、22.12、14.49、25.18、56.28ttg · g-1,respectively.The mean concetrations of six heavy metals in crops were 0.001 1、0.037、0.054、1.153、0.205、0.011 and 9.37 μg · g-1,respectively.Enrichment factor showed that Cd is mainly originated from human sorce;whereas Cr and Ni were controlled by natural sources.Transfer ability of Pb is lower than other metals while transfer ability of Znis higher than other metals.Transfer ability of As、Cd、Cr、Cu、Ni、Pb、Zn in soil-rice system was stronger than those in soil-vegetable and corn systems.Soil pH 、CaO、total organic matter、Fe2O3 、K2O and MgO were major factors influencing metal transfer from soil to crops,whereas soil K2O and MgO contents presented a negative effect on heavy metal mobility in leafed vegetable cultivation systems.