Availability of heavy metals in contaminated vegetable soils from the vicinity of non-ferrous metals mining and smelting areas

The samples of soils and vegetables were collected from the vicinity of non-ferrous metals mining and smelting areas in the districts of Changsha,Zhuzhou,Hengyang and Chenzhou of Hunan Province. The fractions of heavy metals in soils were analyzed by three-stage BCR sequential extraction procedure,the characteristics of clay mineral in soils and the contents of heavy metals in soils and vegetables were determined in order to elucidate the availability and potential environmental risk of metal fractions in contaminated soils. The ratios of total extractable fraction content to the total content for Cd,Cu and Pb are 61.71%,43.14% and 48.84%,respectively. The active fractions of Cd in soils mainly exist as acid-extractable forms,those of As,Cu and Pb mainly exist as reducible forms,and those of Zn mainly exist as acid-extractable and reducible forms. The results show that the combined pollution for active fractions of As,Cd,Cu,Pb and Zn in soils are significant,and the significant relationships between total extractable contents of Cd,Cu and Zn in soils and total contents of those in vegetables are also found through clustering analysis and correlative analysis.