Spatial distribution of concentrations of soil heavy metals in Daxing county, Beijing
北京市大兴区土壤重金属含量的空间分布特征

Seventy surface soil samples were collected from an area of 1039?km~2 in Daxing county of Beijing and analyzed for concentrations of Cu,Zn,Pb,Cr,Cd,Ni,As,Se,Hg and Co. The results of statistical analysis indicated that the concentrations of soil heavy metals all exceeded their background levels, except for As and Se. Only Cd concentration exceeded the critical value of national soil quality standard in some regions. The result of semivariance analysis showed that the metal concentrations were correlated in a given spatial range. Kriging method was applied to estimate the unobserved points and their distribution maps were obtained, which indicated that the soil heavy metal concentrations had a close relationship with soil texture and organic matter contents. The accumulation of soil heavy metals in Daxing county was mainly due to irrigation with water from Liangshuihe, Xinfenghe and Fenghe rivers that have been contaminated with wastewater and sewage. Therefore, some effective countermeasures should be adopted to control wastewater discharge from some factories along those rivers and the discharge should fully meet the national standards.