北京市土壤重金属含量背景值的系统研究

在大规模、系统取样布点的基础上,从803个土壤样品中选出其中120个的"清洁"土壤样品,分析统计后提出了北京市土壤重金属的背景值.研究结果表明,北京市土壤As含量的背景值为7.09 mg/kg、Cd为0.119 mg/kg、Cr为29.8 mg/kg、Cu为18.7 mg/kg、Ni为26.8 mg/kg、Pb为24.6 mg/kg、Zn为57.5 mg/kg.与以前研究中所提出的背景值相比,本研究新提出的土壤Cd背景值提高125%,Pb和Ni的背景值没有明显的差异,但是As、Cr、Cu、Zn的土壤背景值则降低19%～55%.

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.