大型水库热分层的水质响应特征与成因分析

为研究大型水库热分层期间水质的响应特征及成因，于2018年4月—2018年12月对大黑汀水库坝前水体的水温及溶解氧等理化指标进行了连续性垂向监测，在此基础上分析了大黑汀水库季节性热分层变化规律以及各水质指标的响应特征。结果表明：（1）大黑汀水库水体呈典型的单循环混合模式，热分层期间，溶解氧在垂向分布同样表现出季节性变化，且在水体底部出现严重的缺氧现象，但在形成时间上比热分层略有迟滞；（2）氨氮、总磷、磷酸盐以及铁、锰浓度表现为底层 > 中层 > 表层的变化趋势。研究表明，水体热分层会改变水体中溶解氧的垂向分布结构，并进一步导致沉积物向上覆水体释放大量的氮、磷营养盐以及铁、锰等污染物，对水库的正常运行和管理产生不利影响。

Water quality response characteristics and cause analysis of thermal stratification of large reservoirs

To study the response characteristics and causes of water quality during thermal stratification of large reservoirs,a continuity vertical monitoring of water temperature,dissolved oxygen (DO),ammonia nitrogen (NH₃-N), total phosphorus, phosphate, and Fe and Mn were taken in front of the dam of Daheiting Reservoir. The seasonal thermal stratification changes of Daheiting Reservoir and the response characteristics of various water quality indicators to thermal stratification were analyzed, and the causes of vertical changes in water quality were further explored. The results show that the thermal stratification of Daheiting Reservoir is a typical single-cycle mixing model; the mixing period is from October to December and April, and the stable thermal stratification period is May-September (except August); the stable thermal stratification period is from May to September (except August); the vertical distribution of dissolved oxygen also shows seasonal changes;the stratification of DO is one month later than the formation of thermal stratification; the bottom water body became severe hypoxia from June to October (except August); under the effects of thermal stratification and anoxic environment, the contents of ammonia nitrogen, total phosphorus and phosphate in the Daheiting Reservoir during the period from May to July appear as bottom layer > middle layer > surface layer, and the iron and manganese in June and July show the same trend. The research shows that thermal stratification will change the vertical distribution structure of DO, and further lead to a release of nitrogen, phosphorus nutrients and iron, manganese and other pollutants from sediment to water, which will adversely affect the normal operation and management of the reservoir.