暴雨径流对分层水库水质的影响

为探明西安金盆水库热分层演变特征和降雨径流对水库水质的影响，对水库垂向不同点位的水温、溶解氧、浊度、pH、总磷、总氮、氨氮、总有机碳等水质指标进行了持续监测和分析，结果表明：RWCS/H指数能有效判断热分层稳定水平，稳定分层期RWCS/H指数在1.56~6.99 m-1之间；RWCS/H指数与TP、厌氧层厚度显著相关，温跃层的变化特征对厌氧层变化起支配作用，分层期水库底部厌氧条件致使沉积物中营养盐大量释放，其中滞水层TP最高达0.062 mg·L-1；汛期暴雨径流一方面破坏水体热分层稳定性，另一方面携带大量颗粒态污染物以间层流的形式潜入水库中下层水体，使污染负荷提高，TP、TN、NH4+-N、TOC浓度分别达到0.052、1.589、0.42和3.784 mg·L-1；随暴雨径流潜入带来的大量颗粒态污染物和下层水温、pH上升导致沉积物厌氧释放加剧，雨后下层水体TP、TN、NH4+-N、TOC浓度分别达0.022、1.474、0.595和4.559 mg·L-1，显著高于上层水体。分层期内源释放是加快金盆水库富营养化过程的关键因素，汛期暴雨径流引发的水库水环境系统改变使得水质突发性污染风险加大。

Impact of storm runoff on water quality of one stratified reservoir

Continuous monitoring and analysis of vertical indicators of the water quality such as water temperature, dissolved oxygen, turbidity, pH, total phosphorus, total nitrogen, ammonia nitrogen, and total organic carbon were carried out to explore the characteristics of seasonal thermal stratification and the impact of storm runoff on the Xi'an Jinpen reservoir. The RWCS/H index can indicate the stability of thermal stratification effectively, and the results showed that this index was between 1.56 to 6.99 m-1 during the stratification period. RWCS/H is significantly correlated with the concentration of TP and thickness of the anoxic layer. The thermocline dominates the variation of the anoxic layer; nutrients were released from the sediments under anoxic conditions and the maximum concentration of TP was up to 0.062 mg·L-1 in the hypolimnion. On one hand, storm runoff weakens the stability of thermal stratification; on the other hand, it carries large amounts of particulate pollutants in the form of interflow sneaking into the middle and lower regime of the reservoir. Pollution loads increased with the concentration of TP, TN, NH4+-N, and TOC by up to 0.052, 1.589, 0.42 and 3.784 mg·L-1, respectively. The release rates of nutrients from the sediments increase due to the increased particulate pollutants, water temperature, and pH at the bottom. The concentration of TP, TN, NH4+-N, and TOC at the bottom after rain was 0.022, 1.474, 0.595 and 4.559 mg·L-1, respectively, which is significantly higher than that in the upper layer. The endogenous release from the sediment during the stratification period is a key factor increasing the potential of eutrophication of the Jinpen reservoir, and changes in the water environment system caused by storm runoff increases water pollution risks during the flood season.