A regional geochemical survey of soils in Jiangsu Province, China: Preliminary assessment of soil fertility and soil contamination

The regional geochemical survey of soils in Jiangsu Province is an important part of a larger agro-geological survey program in China. This paper presents chemical data from soils sampled at two depths; top-soils from a 0–20 cm depth and sub-soils from a 150–200 cm depth. Results for eleven of the fifty four elements measured are presented for approximately 103,000 top-soils and 26,000 sub-soils. The discussion includes the fertility status and the distribution of soil pH, phosphorous and total organic carbon; and a soil contaminant assessment of eight potentially toxic elements (As, Cd, Hg, Pb, Ni, Cr, Cu and Zn). For a smaller sub-sample from the Nanjing area (3397 top-soils and 834 sub-soils), elemental enrichment factors for twenty eight elements were calculated. From the study, the following conclusions can be made — 1) 50% of the land shows fertility deficiencies as estimated by N, P, K contents and pH; 2) the toxic element contents in about 30% of the land were assessed to be above their natural background concentrations, with over 10% of the land being classified as contaminated; 3) top-soil contamination from toxic elements occurs mainly in urban environments with significant compositional differences between top-soils and sub-soils for many elements, particularly Hg, Cd, Pb, S and Se; 4) the data from regional geochemical surveys of soils can play an important role in studying changes in the ecological environment.