亚热带水库水质特征及沉积物内源污染研究

为探究沉积物内源污染对亚热带分层型水源水库（茜坑水库）夏季水质的影响，采用现场监测和室内模拟相结合的研究手段，于2020年5~9月对茜坑水库深水区水温、溶解氧、氮磷等进行了监测，并采用静态实验模拟法分析了茜坑水库沉积物的耗氧速率及沉积物中氮磷的释放通量.原位监测结果表明，5~9月，茜坑水库水温和溶解氧均处于分层状态，该时期水库底层水体溶解氧含量较低，为沉积物内源污染物的厌氧释放提供了条件；分层期底层水体氨氮和总磷浓度显著高于表层和中层（P<0.01），相应的表层水体氨氮和总磷平均浓度分别为0.062mg/L和0.033mg/L，中层为0.058mg/L和0.037mg/L，底层为0.242mg/L和0.052mg/L.静态模拟实验结果表明，水体及沉积物耗氧均符合零级反应动力学模型（R²分别为0.987，0.989），其中沉积物的耗氧速率处于较高水平，为1.03g/（m²·d），约为水体的1.45倍；沉积物耗氧诱发等温层溶解氧降低并伴随沉积物内源污染释放，其中氨氮的释放极值为0.261mg/L，平均释放通量为7.36mg/（m²·d），总磷的释放极值为0.108mg/L，平均释放通量为2.20mg/（m²·d）.内源氨氮和总磷的释放对水体贡献率分别可达27.98%和38.92%，沉积物氮磷释放对水库水质影响显著.

Water quality characteristics and sediments endogenous pollution of subtropical stratified reservoir

To explore the impact of sediment endogenous pollution on subtropical stratified water source reservoirs (Xikeng Reservoir), a combination of in-situ monitoring and indoor simulation was used to analyze the water temperature and dissolved oxygen, nitrogen and phosphorus in the deep water area of the Xikeng Reservoir from May to September 2020. The oxygen consumption rate of sediments in Xikeng Reservoir and the release flux of nitrogen and phosphorus in the sediments were analyzed by the static experimental simulation method. The results of in-situ monitoring showed that the water temperature and dissolved oxygen in Xikeng Reservoir were in stratified state from May to September, and the dissolved oxygen in the bottom of the reservoir was low during this period, which provides prerequisites for the anaerobic release of endogenous pollutants from sediments. In the stratification stage, the concentrations of ammonia nitrogen and total phosphorus in bottom water were significantly higher than those in surface and middle water (P<0.01). The corresponding average concentrations of ammonia nitrogen and total phosphorus in surface water were 0.062mg/L and 0.033mg/L, respectively, while those in middle water were 0.058mg/L and 0.037mg/L, and those in bottom water were 0.242mg/L and 0.052mg/L. Static simulation experiments showed that the oxygen consumption of both water and sediments was in line with the zero-order reaction kinetics model (R² was 0.987 and 0.989, respectively). The oxygen consumption rate of sediments was 1.03g/(m²·d), which was about 1.45times of that of water. The oxygen consumption of sediment induced the reduction of dissolved oxygenand the release of sediment endogenous pollution. The maximum release value of ammonia nitrogen was 0.261mg/L, and the average release flux was 7.36mg/(m²·d). The maximum release value of total phosphorus was 0.108mg/L, and the average release flux was 2.20mg/(m²·d). The release of endogenous ammonia nitrogen and total phosphorus contributed 27.98% and 38.92% to the water, and the release of nitrogen and phosphorus from sediments had a significant effect on the water quality of the reservoir.