Background value of soil heavy metal in the Three Gorges Reservoir District

The background values of soil heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) were investigated based on extensive investigation in the Three Gorges Reservoir District (TGRD). After analyzing the samples under strict quality control and assurance procedures, the heavy metal concentrations in the soils were calculated using simple statistical method. The background soil values of the heavy metals in TGRD are 5.835 mg·kg^-1 for As, 0.134 mg·kg^-1 for Cd, 78.03 mg·kg^-1 for Cr, 25.00 mg·kg^-1 for Cu, 0.046 mg·kg^-1 for Hg, 29.47 mg·kg^-1 for Ni, 23.88 mg·kg^-1 for Pb and 69.88 mg·kg^-1 for Zn. Compared with the recommended background value by China National Environmental Monitoring Center (CNEMC) in 1990, As and Hg are low, Pb and Zn slightly lower, while Cd and Cr are high and Cu and Ni slightly higher than CNEMC standards. Based on the research, actual conditions are only realistically reflected by continuous field environmental quality appraisal in TGRD, which favors soil environmental quality management.