南水北调中线工程作为缓解我国北方地区水资源短缺问题的重大战略性工程,其水质安全至关重要。中线工程总干渠为封闭型人工渠道,外源污染输入较少,沉积物内源释放是影响其水质安全的重要因素之一。总干渠分水段、退水闸等缓流区域容易淤积沉积物,存在较大的沉积物营养盐释放风险,但目前对缓流区域沉积物释放速率的定量化研究较为缺乏。本研究选取总干渠的典型缓流区域——西黑山进水闸上游段,采用表层沉积物培养法探明其释放速率,揭示不同环境因子对释放速率的影响规律。结果表明:(1)西黑山沉积物总氮的污染指数为4.68,总磷的污染指数为0.548,综合污染指数为3.79,总氮处于重度污染状态,总磷处于轻度污染状态,西黑山沉积物污染严重。(2)西黑山沉积物总磷、总氮、氨氮、硝氮、高锰酸盐指数的释放速率分别为3.77 mg/m2/d、119.81mg/m2/d、312.53mg/m2/d、27.93mg/m2/d、135.16mg/m2/d,沉积物释放风险大,可能对中线水质产生不利影响。(3)温度和pH是影响沉积物释放速率的两个关键因素。温度越高,则总磷、总氮、氨氮、硝氮、高锰酸盐指数释放速率越大,26℃下的释放速率为7℃下的2.41倍~442.04倍。pH中性不利于沉积物污染物的释放,酸性或碱性则均会导致释放速率增加,pH为9的释放速率为pH为7的1.52倍~9.33倍。本研究可为南水北调中线工程沉积物污染评估提供依据,对南水北调中线工程水质安全保障具有重要意义。

As a major strategic project to alleviate the shortage of water resources in northern China, the water quality safety of the Middle Route Project of South-to-North Water Diversion is very important. The main channel of the middle route project is a closed artificial channel, and the input of exogenous pollution is less. The endogenous release of sediments is one of the important factors affecting its water quality safety. The slow-flow areas such as the main canal water diversion section and the retreat sluice are prone to deposit sediments, and there is a large risk of sediment nutrient release. However, there is a lack of quantitative research on the release rate of sediments in the slow-flow area. In this study, the typical slow flow area of the main canal, the upstream section of the Xiheishan intake sluice, was selected. The surface sediment culture method was used to determine the release rate, and the influence of different environmental factors on the release rate was revealed. The results showed that:(1)The pollution index of total nitrogen in the sediments of Xiheisan is 4.68, the pollution index of total phosphorus is 0.548, and the comprehensive pollution index is 3.79. The total nitrogen is in a state of severe pollution, and the total phosphorus is in a state of mild pollution. (2) The release rates of total phosphorus, total nitrogen, ammonia nitrogen, nitrate nitrogen and permanganate index in the sediments of Xiheisan were 3.77mg/m2/d, 119.81mg/m2/d, 312.53mg/m2/d, 27.93mg/m2/d and 135mg/m2/d, respectively. (3)Temperature and pH are two key factors affecting the release rate of sediments. The higher the temperature, the greater the release rate of total phosphorus, total nitrogen, ammonia nitrogen, nitrate nitrogen and permanganate index. The release rate at 26℃is 2.41 times ~ 442.04 times that at 7℃. The neutral pH is not conducive to the release of sediment pollutants. Acidity or alkalinity will lead to an increase in the release rate. The release rate at pH 9 is 1.52~9.33 times that of pH 7. This study can provide a basis for the assessment of sediment pollution in the Middle Route of South-to-North Water Diversion Project, and is of great significance to the water quality safety of the Middle Route of South-to-North Water Diversion Project.

国家重点研发计划(2021YFC3200903)；中国水利水电科学研究院基本科研项目(WE0145C032024)；中国水利水电科学研究院基本科研项目(WE0145C072023)