Interim environmental guidelines for cadmium and mercury in soils of China

A nationwide program is underway in China to establish environmental guidelines with respect to metal levels in soil. There are several factors considered in the formulation of these guidelines but the three major ones are: 1) the soil background content, 2) land use capability, and 3) ecological effect. The guidelines for Hg and Cd in soils of China are formulated based on soil samples collected from 26 provinces (n = 20,300) and by investigating the high background values in 4 mineralized areas. Based on land use capability, the environmental guidelines can be divided into four levels representing: 1) natural or pristine areas, 2) agricultural and pastoral areas, 3) forested areas, and 4) urban and waste disposal areas. The corresponding values are 0.10, 0.20, 0.50, 1.0 mg kg^?1 for Hg; and 0.15, 0.30, 0.50, 1.0 (2.0 for calcareous paddy soil) mg kg^?1 for Cd.