三峡水库磷输移规律研究

三峡水库在发挥防洪、发电、航运等综合效益的同时,也带来了一定的生态环境问题。营养盐磷是水生生态系统的重要生源物质,水库运行拦截泥沙的同时也拦截了部分泥沙所承载的磷。本文利用1997—2017年期间三峡水库的实测流量、含沙量和磷浓度资料,定量分析了三峡水库的磷输移特征,包括时空分布、负荷变化、水库磷拦截率等,旨在明晰三峡水库运行对磷输移的影响。考虑三峡、向家坝和溪洛渡水库开始蓄水时间,将其划分为1997—2002年、2003—2012年和2013—2017年3个时段,分别代表水库蓄水前、三峡水库蓄水、以及上游水库群蓄水。结果表明,库区磷拦截率主要受汛期的磷输移规律的影响;忽略库区区间汇入的影响,基于逐月磷浓度数据可知,2003—2012年,三峡水库的总磷(TP)拦截率为59.8%,溶解磷(DP)拦截率为14.6%;2013—2017年,受三峡入库含沙量大幅减小及点源污染排放增强的影响,DP/TP比值升高,入库磷被更多地输运至下游河道,库区TP和DP拦截率分别减小为14.4%和—18.5%。泥沙对磷输移具有重要的"源"和"汇(缓冲)"作用,但TP与含沙量的关系曲线在汛期与非汛期、不同断面和...

Analysis of phosphorus transport in the Three Gorges Reservoir

The Three Gorges Reservoir (TGR) not only brings into the comprehensive benefits such as flood control, power generation, and navigation, but also brings some ecological and environmental problems. Phosphorus (P) is an important nutrient in the aquatic ecosystem, and the operation of the reservoir results in the retention of both sediment and sediment-associated P. Based on the measured discharge,sediment and P concentrations during 1997-2017, this study quantitatively analyzed the characteristics of P transport in the TGR including the spatial-temporal distribution, flux change, and P interception rate (PIR), to clarify the effects of reservoir operation on the P transport. Considering the dates for the initial operation of TGR, Xiangjiaba Reservoir and Xiluodu Reservoir, the period of 1997-2017 was divided into three periods of 1997-2002, 2003-2012, and 2013-2017, which represented the pre-impoundment period, the operation period of TGR, and that of upstream reservoirs, respectively. The results show that the PIR in the TGR is mainly affected by the characteristics of P transport during the flood season. Based on the monthly data of P concentration, if ignoring the inflow from the reservoir area, the interception rates of total P (TP) and dissolved P (DP) were 59.8% and 14.6% during 2003-2012, respectively. In 2013-2017, the interception rates of TP and DP in the TGR decreased to 14.4% and -18.5%,respectively,due to the significant decrease in the input sediment concentration of TGR and the enhanced point source pollution, which increased the ratio of DP and TP and led to more P transporting to the downstream river. Sediment plays important roles of source and sink in P transport,but the relationship between TP and sediment concentration varies in different sections and different periods.