铜陵矿区河流沉积物重金属的迁移及环境效应

测定铜陵矿区的新桥至顺安河沉积物中5种重金属的全量和形态,并结合环境条件分析它们的迁移变化特征,以阐明不同重金属对河流沉积物环境影响的程度.结果表明,该区域沉积物重金属除Cr外,Cu、Zn、Pb、Cd的均值皆远超长江下游沉积物背景值,其中以Cu和Cd最显著.重金属横向迁移结果显示,矿山重金属会随着沉积物的距离增加而显著降低,新桥河沉积物的迁移变化显著高于顺安河沉积物.重金属Cu、Zn、Pb、Cr皆以残渣态为优势,Cd则以酸提取态为主;迁移过程中Cu、Zn、Cr残渣态逐步增加,毒性减弱;Pb、Cd的活性态比例增大,仍有较高的释放风险.重金属的纵向迁移结果表明,离矿山的位置远近对沉积柱金属的总量和形态起决定作用;新桥河沉积物金属总量高、活性组分多且垂向变化幅度相对较小,说明尾矿堆积速度较快且释放风险较高;顺安河金属总量较低但垂向变化幅度较大,且多种元素的变化趋势不同,说明矿区下游河流沉积物既受尾矿的影响,也受河流流域物质本身的影响.

Spatial migration and environmental effects of heavy metals in river sediments from in the Tongling mining area,Anhui province

The spatial distributions of five heavy metals and their migration characteristics in river sediments of Tongling mining area were discussed in this paper. Based on these results, the environmental influences of heavy metals on sediments were also expounded. The total concentrations and geochemical forms of five heavy metals (Cu, Pb, Zn, Cr and Cd) in sediments were determined in different sites along Xinqiao River and Shun’an River. These results showed that the concentrations of Cu, Zn, Pb, Cd were markedly higher than the background values of heavy metals of the lower Yangtze River sediment, especially for Cu and Cd. The lateral migration of heavy metals along rivers showed that these metals declined rapidly along Xinqiao River, but slowly along Shun’an River. The residual fraction was the dominant form for Cu, Zn, Pb, Cr in sediments from two rivers. Acid-extractable fraction was the dominant form for Cd in sediments. The risks of Cu, Zn and Cr were weakened during migration process, due to increasing residual fractions. But the active forms of Pb and Cd increased in the downstream, which will rise the ecological risk. Vertical changes of heavy metals in sediment cores showed that the concentrations and forms of heavy metals relied on the locations of sediment cores. The core sediment in Xinqiao river had the higher concentrations and more active forms of heavy metals, but smaller changes in the profile compared to the core sediment in Shun’an River. It reflected the faster accumulation rate and higher release risk for tailing-bearing sediment. The core sediment in Shun’an river showed the lower contents of heavy metals and significant fluctuations in the sediment profile. It reflects the heavy metals of sediments from mining rivers are not only influenced by mining tailings, but also by erosion material in the watershed.