乌江渡沉积物磷的污染特征及其对河流筑坝的响应

Characteristics of Phosphorus in Sediment of the Wujiangdu Reservoir and Its Responses to Damming

受息烽河输入的影响,乌江渡水库的磷污染问题一直备受关注,但水库上游水体磷的释放以及河流筑坝对水库磷污染的影响却没有引起太多的重视。本文通过对表层沉积物和沉积物柱芯中磷及其形态的分析,研究乌江渡沉积物磷的污染现状和历史变化趋势及其对河流筑坝的响应。结果表明:1)乌江渡水库沉积物磷污染现已非常严重,远高于国内其他湖库;2)乌江渡沉积物磷含量从上游至下游有递增的趋势,且主要由NaOH-P的增加所致;3)乌江渡沉积物磷的空间变化可能源于不同粒径颗粒物或藻类的沿程沉降,也可能源于水体中Fe^(2+)被氧化后引起磷的沿程沉降,但真实原因还需要进一步的证实。这说明上游水库滞留在沉积物中的磷部分可能重新释放出来,导致乌江渡水库中上游沉积物磷的污染也相当严重。

Phosphorus pollution in the Wujiangdu Reservoir has been a matter of serious concern,due to the input of phosphorus from Xifeng River.However,the release of phosphorus from the upstream and the influence of damming on the phosphorus pollution in the Wujiangdu Reservoir have little concerned.Based on the analysis of phosphorus and its geochemical forms in surface sediments and sediment cores,the current situation and historical trend of phosphorus in Wujiangdu sediments,as well as its response to river damming,were investigated.The results showed that:1)the phosphorus pollution in sediments of the Wujiangdu Reservoir was highly serious,which is much more serious than that of other lakes or reservoirs in China;2)phosphorus contents in sediments of the Wujiangdu Reservoir increased from the upstream to the downstream,mainly caused by the increase in NaOH-P in the sediments;3)spatial variation of phosphorus in sediments may be caused by the settlement of particles or algae along the flow direction,or by the deposition of phosphorus caused by the oxidation of Fe^(2+) in water,but the real reason needs further confirmation.This study indicated that sedimentary phosphorus detained in the upper reservoir may be released again,leading to the serious sedimentary pollution of phosphorus in the upper and middle reaches of the Wujiangdu Reservoir.