Heavy metals contents in soil profiles of typical agricultural lands in Yixing, Jiangsu Province, China

Abstract

The effect of land use pattern on the heavy metals (HMs) distribution in soil profiles was investigated in Yixing City, China, for the four typical types of land utilization, i.e. vegetable fields on the plain, paddy fields, tea gardens on hilly lands and bamboo groves. The variance of HMs concentration in the depth of 0–15 cm, 15–30 cm, 30–60 cm of soil profiles was compared among the different tillage ages. Results showed there was a notable accumulation of Cd, Hg, Cu, Pb, Zn and Cr in the soil profiles of vegetable fields and paddy fields causing a pollution of Cu, Hg and Cd in some profiles, while no remarkable accumulation of HMs in the soil profiles of the tea gardens and bamboo groves was found. The accumulation extent of HMs in the soil profiles of the four kinds of land use followed a sequence of vegetable fields>paddy fields>tea gardens>bamboo groves. The accumulation of HMs was mainly due to the industry, transportation, other urban human activities, and intensive use of fertilizers and pesticides. The downward leaching of HMs was relatively remarkable in the soil profiles of vegetable fields. There was an accumulation in surface and subsurface layers for Cd, Hg, Pb, Zn in the soil profiles of paddy fields and tea gardens, and for Cd, Hg in those of bamboo groves. Serious pollution effects of Hg, Pb, and Zn have been shown in the soil of vegetable fields. All the four kinds of agricultural land are basically free from the pollution of the external sources of As and Ni. With the increase of tillage time, the soil of vegetable and paddy fields will face the potential risk of HMs pollution, which mainly comes from Hg, Cd and Cu, whereas that of tea gardens and bamboo groves faces a relatively small risk.