北京市大兴区土壤重金属含量的空间分布特征

Spatial distribution of concentrations of soil heavy metals in Daxing county, Beijing

在面积为1039km2的北京市大兴区布设了70个取样点,测定了其表层土壤重金属Cu、Zn、Pb、Cr、Cd、Ni、As、Se、Hg和Co的含量.统计结果表明,除As和Se外,其它重金属平均含量均高于其背景含量.只有个别地方Cd的含量超过了国家二级标准限值,而其余重金属含量均没有超过其二级标准.通过半方差函数分析,发现10种重金属元素在一定范围内均存在空间相关性.采用Kriging最优内插法得到了表层土壤重金属含量的空间分布图,发现土壤重金属含量与土壤质地和有机质含量关系密切.目前大兴区土壤重金属的主要来源是污灌,特别是来自凉水河、新凤河和凤河的污水,应重点对这些河流周围的排污企业进行治理,严格执行达标排放.

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.