上海中心城区地表灰尘与土壤中重金属累积及污染评价

Heavy Metals in Urban Dusts and Soils of Shanghai and Its Pollution Assessment

通过对上海中心城区土壤与地表灰尘和降雨径流样品的取样调查,探讨了城市不同土地利用类型中重金属Cu,Zn,Cr,Pb的累积特征及其环境效应.结果显示:地表灰尘、土壤重金属在不同土地利用类型中的富集程度均高于土壤背景值,且存在显著性差异.相比之下,灰尘重金属污染比土壤严重,同一土地利用类型灰尘重金属P值为土壤的3～4倍.土地利用方式对重金属在地表灰尘和土壤中的积累有较明显的影响.地表灰尘重金属在工业、交通、居住用地中的含量普遍偏高,而在绿地中的含量普遍较低;土壤重金属在交通、商业和绿地中浓度较高,而工业用地中浓度较低.不同土地利用方式对地表径流重金属含量的影响不同,与土壤相比,地表灰尘直接影响到降雨径流重金属含量,两者之间耦合关系明显.工业、交通、居住和商业用地地表径流中,重金属EMC值以工业用地最高,其次为交通用地,商业和居住用地较小,但Cr,Pb,Zn的平均EMC值都超过了国家Ⅴ类水的标准,具有潜在的环境危害.

Through the investigation of 5 types of land use in Shanghai central city, including industrial, residential, traffic, greenbelt and commercial areas, heavy metals concentrations of 69 urban dusts, topsoils and 3 urban runoff samples were obtained. Compared with background concentrations, the heavy metal concentrations in urban dust and topsoils are much higher. The comprehensive pollution indexes in urban dusts and soils of the five land use types vary from 67.1 （residential area）, 40.3 （green belt）, and 22.9 （traffic area） to 12.5 （industrial area）, respectively. Both the dusts and soils are all polluted, especially due to the high concentration of Pb, Zn, and Cr. The urban runoffs EMCs （event mean concentration） of Cr, Pb and Zn in all land uses are high than V of the national standard. So the urban runoff will greatly influence the urban river water quality. Commonly, the heavy metal average contents of urban dusts are high in industrial, traffic and residential area and low in commercial area and green belts. When con cerned the topsoils, however, the commercial area has the highest Cu content （75.2 mg·kg^-1） and the lowest Pb content （455 mg·kg^-1）, the traffic area has the highest Zn content （2 960 mg·kg^-1）; the residential area has the highest Pb （595 mg·kg^-1） and Cr （627 mg·kg^-1） contents. According to the EMCs in the urban runoff, the industrial area has the highest content of all 4 heavy metals and the EMCs of Cr, Pb, Zn, Cu in industrial are 6. 9 mg·L^-1, 500 mg mg·L^-1, 3. 9 mg·L ^-1 and 2. 3 mg·L^-1. The runoff around the industrial area, therefore, should be considered seriously. According to the EMCs in the urban runoff, the order of the rest land use types, from the highest to the lowest Pb, Cr and Zn concentration,is traffic area, resi dential area and commercial area.