巢湖表层沉积物中重金属总量及形态分析

Chemical Speciation and Total Concentration of Heavy Metals for Sediments from Lake Chaohu

对巢湖湖区东西南北4个不同方位、5个采样点的巢湖表层沉积物中Cr、Mo、Ni、Hg、Cd、Zn、As、Pb、Mn、Cu等十种重金属分析,发现巢湖底泥中的重金属浓度总体以靠近合肥的西北部最高、东北部其次、南部最低,但污染都尚未超标.对其中Hg、Cd、As、Pb四种重金属的化学形态分析结果表明,巢湖底泥中Hg、As和Pb都以非有效态和中等可利用态为主,其中As腐质酸结合态比例较大,Pb的铁锰氧化态比例较大,具有一定的潜在危害性;而Cd的离子交换态因比例较大具有直接危害性.与太湖进行比较发现,尽管太湖底泥Pb和Cd重金属全量高于巢湖,但形态分析结果表明,这两种重金属的活性却是巢湖大于太湖,因此对巢湖重金属污染的防治比太湖更要加以重视.

Total concentration of ten elements, namely Cr, Mo, Ni, Hg, Cd, Zn, Pb, Mn and Cu, were determined in 5 bottom sediments in Lake Chaohu. The results indicated that pollutions mostly existed in the Northwest part of the lake near Hefei, with lower concentration in the Northeast and the lowest concentration in the South. But the heavy metal pollution in Lake Chaohu is not serious. The speciations of As, Hg, Pb and Cd were analyzed using a sequential extraction procedure. It is found that the residual fraction is generally high. Among the four metals, organic As has the highest percentage of its chemical fractions. The Pb bound to the Fe-Mn fraction is the important phase. While the percentage of the exchangeable Cd that is easily bioavailable is high. Compared with Lake Taihu, Pb and Cd in Lake Chaohu is more bioavailable than in Lake Taihu, though the total concentration of the two metals is higher in Lake Taihu.