向家坝水电工程蓄水后坝下河段水质现状分析

Water quality present situation under the Xiangjiaba dam after impounding

为掌握向家坝蓄水后坝下河段的水质现状,本研究在坝下长江上游珍稀、特有鱼类国家级自然保护区内选取六个断面,在鱼类不同的生活阶段进行监测。基于蓄水后2013-2014年水环境因子的监测数据,对各断面的21项水质指标的总体特征进行研究,分析其变化规律并进行水质评价得出目前水质现状。结果显示,蓄水后该江段水质指标特征总体良好,水温初期滞温变化值在2℃左右,超标因子主要是总氮、总磷、高锰酸盐指数、挥发酚以及重金属铅汞。总氮、砷及六价铬差异性极显著,是影响数据差异的众多因素中的主要因素。对各样点的水质因子进行聚类分析表明,坝下三块石与其他地点分类明显,距大坝较远与较近的点位各指标存在较大的差异性,表明大坝蓄水对水质带来不同程度的影响。

In order to master water quality variation under the Xiangjiaba dam,this study chose six representative cross sections from Sankuaishi to Mituo along national nature reserve of rare and endemic fish in the upper Yangtze River in fishes different life periods. Based on the water environment monitoring data from 2013 to 2014 year,the change rule of the 21 water quality index and the present situation water quality of this area were analyzed,and water quality evaluation were carried on. The result showed that water quality characteristics were generally good after impoundment in this area and the initial temperature delay value about 2 ℃. The excessive indices mainly were the total nitrogen,total phosphorus,potassium permanganate index,volatile phenol,ammonia nitrogen and heavy metal Hg. Difference of total nitrogen,arsenic and hexavalent chromium was so particularly significant that became the main of many factors affecting the data gap. The cluster analysis of water quality indices showed that Sankuaishi was significantly different with others,and the greater difference of each index between other locations far from the dam and close to the point showed that dam impoundment brought different extent impacts of water quality.