西湖和东苕溪沉积物重金属化学形态分析

不同赋存形态重金属的环境行为和生态效应不同,水体沉积物中重金属的迁移转化及其潜在环境危害更大程度上取决于其赋存形态。本研究在西湖和东苕溪设置12个采样点采集沉积物样品,采用改进BCR分步提取法,提取了重金属污染物的4种化学形态,分别为弱酸提取态、可还原态、可氧化态及残渣态。结果表明:沉积物中Cd以弱酸提取态为主,对外界环境的变化极其敏感,并易于发生迁移转化,生态风险较高。Cu离子对有机质表现出极强的亲和力导致Cu的可氧化态含量较高也有一定的生态风险。Pb会被Fe-Mn氧化物所吸附导致Pb的可还原态含量较高,存在较高的潜在生态危害。Mn的弱酸提取态、可还原态和残渣态含量都较高,在迁移的过程中变化地较快,能够逐渐降低Mn对自然环境的危害。其他各重金属(As、Cr、Zn)则都以残渣态为主,潜在危害较低。

Chemical Speciation of Heavy Metals in the Sediments of West Lake and East Tiaoxi Basin

The different forms of heavy metals have the different environmental behaviors and ecological effects.The migration,transformation,and potential environmental harm of heavy metals in sediments depend on their occurrence forms in ecosystem.In this study,12 sediment samples were collected in the West Lake and the East Tiaoxi.The four chemical forms of heavy metal pollutants were extracted(water/acid soluble state,reducible state,oxidizable state and residual state)by the improved BCR step extraction method.The results showed that a predominance proportion of Cd is presented as water/acid soluble state,which is sensitive to the variation of the ecosystem and prone to migrate,has a high ecological risk.Cu ions showed a strong affinity for organic matter,which leads to a high content of oxidizable state of Cu,has a certain ecological risk.Pb can be adsorbed by Fe-Mn oxide,resulting in a high content of Pb reducible state,which has a high potential ecological risk.Mn has a high content of water/acid soluble state,reducible state and residual state,and changes rapidly in the migration.It could gradually reduce its harm to the ecosystem.Other heavy metals(As,Cr,Zn)are mainly in the residue state and have low potential hazards.