蠡湖沉积物重金属形态及稳定性研究

以蠡湖及其入湖河口为研究对象,采用连续分级提取法研究了表层沉积物中Cr、Ni、Cu、Zn、As、Cd、Hg和Pb形态的空间赋存特征,同时结合各金属在间隙水体中的空间分布,探讨了各形态金属的稳定度及其生物有效性.结果表明,间隙水体及表层沉积物可提取态金属分布都具有明显的空间异质性,Cr、Cu、Zn、Pb的高值区沿宝界桥和蠡湖大桥呈"带状"分布,Ni、As、Cd、Hg的高值区沿河口向湖区扩展,呈"扇形"分布,并且含量都在退渔还湖区较低.沉积物中Cd、Cu、Ni的可提取态占总量的质量分数较高,分别达到71.02%、54.79%和50.62%,其余金属则主要以残渣态为主.8种金属稳定性顺序为Cr>Pb>Hg>As>Cu>Ni>Zn>Cd,Cd和Zn在大部分点位处于不稳定状态,快速解吸释放的风险较大.间隙水体毒性评估表明,各金属不会对水生生态系统产生急性毒性,但部分区域尤其是入湖河口的Hg和Pb可能会对底栖生物产生慢性毒性.

Heavy Metal Speciation and Stability in the Sediment of Lihu Lake

The spatial occurrence characteristics of the speciation of Cr, Ni, Cu, Zn, As, Cd, Hg and Pb in sediments of the lake body and river mouths of Lihu Lake were studied. Meanwhile, combined with the spatial distribution of metals in interstitial water, the stability and bio-availability of various forms of studied metals were discussed. The results showed that metals in interstitial water and extractable metals in surface sediments both had obvious spatial heterogeneity, and the metal contents in retreated fishery district were lower. High value areas of Cr, Cu and Zn distributed in belt along Baojie Bridge and Lihu Lake Bridge, and the high value areas of Ni, As, Cd, Hg distributed in sector extending from river mouths to the lake body. Most metals mainly existed in residue state except for Cd, Cu and Ni, the extractable content of which respectively accounted for 71.02%, 54.79% and 50.62% of the total content. The stability of eight studied metals was in the order of Cr >Pb >Hg >As >Cu >Ni> Zn> Cd. Cd and Zn were unstable in most studied sites, so there was higher risk of quick desorption and release. Toxicity assessment of interstitial water showed that the tested metals would not pose acute toxicity for aquatic ecosystem, but Hg and Pb in some districts, especially in the river mouths, might pose chronic toxicity for the benthonic organisms.