北京东郊污水与清水灌区土壤中重金属含量的比较研究

Comparative study of heavy metal contents in soil from irrigated areas of east suburb,Beijing

运用遥感影像对北京东郊的凤港减河、北运河、潮白河并行区进行实地调查,在污水灌区、清污混合灌区、清水灌区采集土壤样品,比较分析了不同类型灌区土壤中重金属含量的分布特征。结果表明,与研究区土壤背景值相比,在污水灌区、清污混合灌区、清水灌区的表土层和心土层中重金属元素Co、Ni、Mn和V没有出现明显积累现象;污水灌区和清污混合灌区表土层中重金属元素Cr、Cu和Zn具有明显的积累现象。污水灌区表土层中Cr平均质量比达84.20mg/kg、Cu平均质量比达25.67mg/kg、Zn平均质量比达105.20mg/kg,均高于清水灌区表土层中对应元素的平均质量比,也均高于污水灌区心土层中对应元素的平均质量比,这可能是由于研究区的碱性土壤、土壤中CaCO3和有机质对这些重金属具有一定的吸附和固结作用,从而降低了这些重金属元素的活性。潮白河沉积物中Co、Cr、Cu、Mn、Ni、V和Zn质量比平均值分别达到19.07mg/kg、67.19mg/kg、20.81mg/kg、610.64mg/kg、26.84mg/kg、84.97mg/kg、112.37mg/kg,均与研究区土壤背景值相当;北运河及凤港减河沉积物中Co、Mn、Ni和V质量比平均值分别为18.70mg/kg、628.47mg/kg、52.00mg/kg、69.67mg/kg,也均与研究区土壤背景值相当;而北运河及凤港减河沉积物中Cr、Cu、Zn平均质量比分别为160.96mg/kg、184.57mg/kg、533.48mg/kg,均明显地高于研究区土壤背景值,这表明引用北运河和凤港减河的污水灌溉是造成土壤中Cr、Cu、Zn质量比增高的主要原因。

Basing on the analysis of land use and remote sense image of irrigated area distributed in Beijing east suburb, this paper investigates the distribution characteristics of heavy metal in soil from sewage, mixed and clear water irrigation area. The result shows that Co, Ni, Mn and V contamination has not been observed in both topsoil and subsoil compared with the background value in the study area. Cr, Cu and Zn contamination has been found in the topsoil of sewage and mixed water irrigation area. According to national soil environment quality standard （GB 15618--1995）, the subject of soil from the sewage and mixed water irrigation area keep in national standard Ⅰ, and some individual sampling point are up to the standard Ⅱ. It suggests that the long-term sewage irrigation may lead to the intensification of soil environment contamination risk. The mean content value of Cr, Cu and Zn in topsoil of sewage irrigation area are 84.20, 25.67 and 105.20 mg/kg respectively, and are higher than those of subsoil from sewage irrigation area and topsoil from mixed irrigation area. Furthermore, a significant correlation was found between soil organic matter content and heavy metal accumulation in soil, and a correlation between CaCO3 content and heavy metal accumulation is confirmed. These results suggest that the soil organic matter and CaCO3 affect the immigration of heavy metals in soil. The mean content value of Co, Cr, Cu, Mn, Ni, V, Zn in sediments sampled from Chaobai River are 19.07, 67.19, 20.81, 610.64, 26.84, 84.97, 112.37 mg/kg respectively. The content mean value of Co, Cr, Cu, Mn, Ni, Y, Zn in sediment sampled from Beiyun River are 18.70, 160.96, 184.57, 628.47, 52.00, 69.67, 533.48 respectively. The difference of heavy metal content in sediments between Chaobai river and Beiyun river suggest that the origins of heavy metal contamination in soil may be mainly explained by the sewage irrigation.