太湖MS岩芯重金属元素地球化学形态研究

Speciation of heavy metals in Lake Ta ihu sediments of Core MS

采用BCR三步提取法对太湖MS岩芯沉积物中Cu、Fe、Mn、Ni、Pb和Zn等6种重金属元素的化学形态进行了研究。结果表明,有效结合态的Cu、Ni和Pb主要以有机物及硫化物结合态、Fe-Mn氧化物结合态存在,Fe和Zn主要以Fe-Mn氧化物结合态存在,Mn主要以可交换态及碳酸盐结合态存在;Fe-Mn氧化物结合态的Ni、Pb和Zn与可还原态的Mn有较好的正相关关系,有机物及硫化物结合态的Cu、Mn、Ni、Pb和Zn与有机碳含量有较好的正相关关系;重金属形态分布体现了重金属元素地球化学性质的差异,以及重金属形态含量与沉积物理化性质的关系。沉积岩芯重金属元素形态垂向变化规律及次生相富集系数表明,Cu、Mn、Ni、Pb和Zn在沉积岩芯13～4cm有效结合态含量较稳定,为自然沉积;4～0cm有效结合态含量明显升高,存在一定程度的人为污染。根据137Cs测年结果判断,沉积岩芯Cu、Mn、Ni、Pb和Zn等重金属污染开始于20世纪70年代末期,主要污染元素及污染历史与太湖流域污染工业类型及经济发展阶段相吻合。

The BCR sequential extraction proce dure is applied to the speciation of heavy metals(Cu,Fe,Mn,Ni,Pb and Zn)in lake sediments of Core MS in Lake Taihu,and the error analysis of BCR method is also performed.The results show that the BCR method h as better stability for the extracti on of speciation of heavy metals in th e lake sediments.In the extractable forms of the heavy metals,Cu,Ni and Pb are mainly associated with organic /sulp hide fractions and Fe-Mn oxide fractions;Fe and Zn mainly with Fe-Mn oxide fra ctions;and Mn mainly with exchangeable and carbonate fractio ns.The organic /sulphide fractions of Cu,Mn,Ni,Pb and Zn have good correlation with TOC,and the Fe-Mn o xide fractions of Ni,Pb and Zn have good correlation with Mn of Fe-Mn oxide fraction,which reflects the geochemical properties of the heavy metals and their correlation with the physiochemical characteristics of the sediments.T he variations of the speciation in Co re MS can be divided into two periods:the extractable forms of the elements have stable concentrations between 13and 4cm,which indicates the nature sources of the heavy metals;all the e xtractable forms of the heavy metals show high values in the top 4cm sediments,indicating the anthropogenic inputs of heavy metals from the rapid industrial,agricultural and domestic sources during recent 20years in the Lake Taihu basin.The pollution elem ents and their pollution history reflected by the sediments of Core MS are in agre ement with the economy types and seed time of Lake Taihu basin.Results from this study are useful in accessing the chemical changes,pollution a nd the releasing into the water envir onment of heavy metals in Lake Taihu sedimen ts.