[Background concentrations of soil heavy metals in Beijing].

Soil background concentrations of heavy metals are important criterion for the assessment of soil environmental quality. The background concentrations of soil heavy metals, As, Cd, Cr, Cu, Ni, Pb and Zn, were investigated based on an extensive investigation conducted in the whole area of Beijing. About 120 soil samples taken from the area without pollution of heavy metals were selected from the total 803 soil samples. After analyzing the samples with strict quality assure and quality control (QA/QC) procedures, the heavy metal concentrations in the soils were calculated using statistical method. The revised background concentrations of the soils in Beijing are proposed to be 7.09 mg/kg for As, 0.119 mg/kg for Cd, 29.8 mg/kg for Cr, 18.7 mg/kg for Cu, 26.8 mg/kg for Ni, 24.6 mg/kg for Pb, 57.5 mg/kg for Zn, respectively. Compared with the concentrations suggested by China National Environmental Monitoring Center (CNEMC) in 1990, the Cd background concentration suggested in present study is about 125% higher than that of CNEMC, and the As, Cr, Cu, Zn concentrations are 19%-55% lower than those of CNEMC, while the concentrations of Pb and Ni are not obviously different from those of CNEMC.