南宁市郊周边农田土壤-农作物系统重金属元素迁移特征及其影响因素

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

通过采集南宁市郊农田中玉米、蔬菜、水稻可食部分及其根系土150组,研究重金属元素在不同土壤-农作物系统中迁移特征及其影响因素,结果表明:根系土中Hg、Cd、Cr、Cu、Ni、Pb、Zn平均含量分别为0.116、0.202、56.76、22.12、14.49、25.18和56.28 mg·kg^(-1)。农作物对应平均含量分别为0.001 1、0.037、0.054、1.153、0.205、0.011和9.37mg·kg^(-1)。根系土富集因子表明Cd受到不同程度人为活动影响,Cr和Ni主要受地质背景控制;不同作物系统元素富集因子表明Pb在土壤-农作物系统中迁移能力最低,Zn迁移能力最强。Cd、Cr、Cu、Ni、Pb和Zn在土壤-水稻系统重迁移能力显著高于蔬菜和玉米。根系土中pH、CaO、有机质、Fe_2O_3、K_2O、MgO与重金生物富集系数呈显著性负相关,但在土壤-叶类蔬菜系统中根系土中K_2O、MgO与Hg生物富集系数呈显著正相关。

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、56.28μg·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 9.37μg·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 Zn is higher than other metals.Transfer ability of As、Cd、Cr、Cu、Ni、Pb、Zn in soilrice system was stronger than those in soil-vegetable and corn systems.Soil pH 、CaO、total organic matter、Fe2 O3、K2 O and MgO were major factors influencing metal transfer from soil to crops,whereas soil K2 O and MgO contents presented a negative effect on heavy metal mobility in leafed vegetable cultivation systems.