玄武湖沉积物中重金属的垂直分布

选取中国典型城市内湖--南京玄武湖为研究对象，采用目前运用较为广泛的欧洲标准测试分析委员会(now the Standards，Measurements and Testing Programme)推荐的BCR连续提取法对沉积物中Pb、Cd、Ni、Zn、Cr和Mo 6种重金属形态在垂向上的分布进行测定，并对其潜在迁移风险进行讨论。结果表明：玄武湖沉积物中6种重金属总量由大到小的顺序为：Zn＞Cr＞Mo＞Ni＞Pb＞Cd，含量分别为14880~24412、11255~13578、5519~7730、4142~4981、857~2005和129~173 mg/kg，除Pb外均高于南京土壤环境背景值。在50 cm的柱状沉积物样品中，Pb与Cd主要以可氧化态和残渣态存在，Mo、Ni、Zn和Cr主要以残渣态为主要的存在形态。6种重金属的总量与不同形态在垂向上的分布因金属种类不同有所差异。玄武湖沉积物中含有丰富的有机质(80%~110%)，且pH值为偏酸性至近中性(582~713)，沉积物中的重金属具有较高的潜在迁移风险，在城市湖泊污染治理中应予以足够的重视

VERTICAL DISTRIBUTION OF FRACTIONS OF Pb|Cd|Ni|Zn|Cr AND Mo IN SEDIMENTS OF AN URBAN LAKE

Total contents of Pb，Cd，Ni，Zn，Cr and Mo in sediments of Xuanwu lake，a shallow urban lake，were determined，and the chemical fractions of these metals were also investigated using BCR’s sequential extraction procedure to evaluate the vertical distribution of metals in the sediment and their potential mobility.The results showed that metal total contents were in the order of Zn (14880~24412 mg/kg)>Cr (11255~13578 mg/kg)>Mo (5519~7730 mg/kg)>Ni (4142~4981 mg/kg)>Pb (857~2005 mg/kg)>Cd (129~173 mg/kg).Except for Pb，all these contents exceeded the background values of soils in Nanjing city.In the 50 cm sediment profile，Pb and Cd were mainly in the oxidizable and residual fractions，while Mo，Ni，Zn and Cr distributed mainly in the residual fraction.The vertical distribution of total metal contents and their fractions varied greatly.Because the pH of the sediment of Xuanwu lake leaned to acidic or near neutral (582~713)，it can be assumed that the exchangeable and reducible fractions are vulnerable，and the risk can be high for the potential release of Zn，Mo，Ni and Cd.The abundant organic matter (80%~110%) in the sediment reveals the potential mobility of oxidizable fraction，which can be degraded over the time.The high percentages of Pb (7550%) and Cr (4238%) in the oxidizable fraction imply the potential risk of mobility.Enough attention must be paid to the risk of heavy metals release during the processes of pollution control of urban lakes.