北京东南郊农田土壤重金属含量与环境质量评价

采集北京市大兴区长子营镇58份土壤耕层样品,分析其中Cu、Zn、Cr、Pb、Ni、As、Cd和Hg 8种重金属含量,其平均含量分别为23.1、59.6、61.8、19.5、23.8、4.7、0.16和0.07 mg·kg-1,8种重金属元素含量平均值均未超出土壤环境质量一级标准,但Cu、Zn、Cr和Cd的平均含量由于受人类活动的影响已经高出北京地区环境背景值。皮尔逊相关系数分析结果表明,Cu、Cr、Zn、Ni与Cd 5种重金属,Zn与Hg,Cr与Pb具有相同来源的可能性较大。在国家土壤环境一级标准下各元素的单因子污染指数均小于1,顺序为CdCrCuZnNiPbHgAs,综合污染指数为0.70。分析不同土地利用类型的土壤重金属单因子指数与内梅罗指数,设施菜田、露地菜田、粮田和果园的内梅罗指数分别为0.88、0.91、0.61和0.59。长子营镇重金属的空间分布特征为中、北部含量高于南部,尤其以中部地区含量最高。总体来说,研究区域内土壤环境质量总体安全,部分地区土壤重金属含量接近临界处于警戒水平。

Heavy metals contents and environment quality evaluation of farmland soil in east south area of Beijing

Fifty-eight samples of surface farmland soils collected from suburbs of Zhangziying in Daxing district, were moni-tored for total contents of 8 heavy metals by a accumulative index. Results showed that the average concentrations of Cu, Zn, Cr, Pb, Ni, As, Cd and Hg were 23. 1, 59. 6, 61. 8, 19. 5, 23. 8, 4. 7, 0. 16 and 0. 07 mg·kg-1 respectively. All of which were below soil environmental quality standard classⅠ. But average concentration of Cu, Zn, Cr and Cd exceeded the background value of Beijing area. At the same time, Correlation analyses showed that the five heavy metals ( Cu, Cr, Zn, Ni and Cd) probably came from the same recourses, and so did of Zn and Hg, Cr and Pb. According to the soil heavy metals environmental quality standards classⅠ, the Nemerow aggregate pollution index of all the heavy metal was 0. 70, and the sin-gle factor index was in order of Cd>Cr>Cu>Zn>Ni>Pb>Hg>As. The Nemerow indices of soil in bare vegetable field, greenhouse vegetable field, grain crop field and fruit field were 0. 88, 0. 91, 0. 61 and 0. 59, respectively. The spatial distri-bution characteristics of heavy metal was north-central higher than the south, especially the central region exhibited the highest levels. As a whole, most of the soil environment quality was at safe level and the pollution of heavy metal for some areas was at the alert level.