贵州阿哈水库沉积物中重金属二次污染的趋势分析

TREND ANALYSIS OF THE RECYCLING OF HEAVY METALS IN SEDIMENTS OF AHA LAKE,GUIZHOU PROVINCE

通过对受矿山活动影响的贵州阿哈水库沉积物-水界面的模拟试验及实测分析,从水库水质安全角度讨论了沉积物中蓄积的重金属作为二次污染源的可能性。研究发现:在水体季节性缺氧期间,沉积物中部分重金属元素将大量释放到水体中,严重威胁水质安全。Fe,Mn的最大释放发生在水体缺氧事件的50小时内。而Co,Cu,Ni,Pb等元素总体释放量较小,并主要在10小时内达到最大释放。对比其他地区,阿哈水库中重金属元素具有更强的界面扩散作用。锰的扩散通量在季节上表现为:冬季>秋季>春夏季。而铁的扩散通量则为:春夏季>秋季>冬季。锰的界面扩散通量远大于铁的界面扩散通量,表明界面附近锰的循环极为剧烈且远强于铁。这对其他重金属元素的界面循环产生了重要影响。界面附近的铁、锰、硫循环对重金属迁移有着显著的控制作用。受到氧化还原条件的影响,重金属扩散通量在季节上变化较大。

In this study, a mining drainage impacted reservoir, Aha Reservoir, was investigated. By means of simulation experiment of sediment cores and the chemical analysis of pore water, the potential of heavy metals in sediments to release into the overlying water body was discussed from the view of water quality safety. Results showed that, some heavy metal can re-enter into the reservoir water and seriously endanger the water quality, during the period of seasonally oxygen depletion of reservoir water. The maximal releasing fluxes of Fe and Mn occurred within 50 hours when oxygen depletion in bottom water, whilst Co, Cu, Ni, Pb can reach to their maximal releasing within 10 hours, with lesser fluxes than Fe and Mn. Compared with that in other areas, heavy metals in sediment in Aha Reservoir have stronger diffusive fluxes. Seasonally, diffusive fluxes of Mn is winter〉autumn〉spring and summer, and that of Fe is spring and summer〉autumn〉winter. As diffusive fluxes of Mn is significantly larger than that of Fe, recycling of Mn near sediment-water interface should be more active than Fe cycling, which has obvious impact on the interface recycling of other heavy metals. However, Fe-Mn-S cycling near the sediment water interface controls the up and down move of heavy metals. The diffusion flux of heavy metals has obvious fluctuation in different seasons, due to the changes in the redox potential.