三峡水库蓄水后对支流大宁河富营养化特征及水动力的影响

摘要

三峡水库蓄水后支流大宁河水华频发,为了揭示水库蓄水以来,大宁河富营养化变化趋势以及水华暴发期间水动力等环境因子的影响特征,自2005年长期跟踪监测大宁河的水质状况,并于2010年针对东坪坝库湾2次典型水华事件,初步探讨了水华暴发期间的主要影响因素.结果表明:2005年以来,大宁河水体处于中度营养状态,水质尚好,但低估了水华敏感期的富营养化状况.东坪坝3月水华暴发期间,叶绿素a浓度与流速呈显著负相关,与pH、DO也呈显著相关,表明在此次水华期间,流速对藻细胞的增殖或聚集产生直接或间接的影响,pH和DO是引起水华暴发的主要水质因子；5月水华暴发期间,叶绿素a浓度与流速呈显著负相关,与流量呈显著正相关,同时与pH、透明度(SD)呈显著相关,表明在这次水华期间,流速和流量都对藻细胞增殖或聚集产生直接或间接的影响,pH和SD成为水质敏感因子.3月和5月水华暴发时间分别处于水库高水位运行期和泄水期,这可能是导致水华影响因子不同的主要原因,但具体机理还有待于进一步研究.本文结果表明在三峡水库调度运行的不同阶段支流库湾水华暴发的机制不同,需要针对不同时段支流库湾水环境特征分别加以调查研究.%Algal blooms have occurred frequently in the backwater region of the Daning River branch since the impoundment of the Three Gorges Reservoir( TGR). In order to assess the water quality status and the driving factors on algal bloom outbreak, the wa-ter quality has been monitored since 2005, and 2 typical algal blooms, occurred in Dongpingba in March and May 2010, were in-vestigated. Results showed that Daning River was mesotrophic and water quality was good, nevertheless the trophic grade was un-derestimated for the period of algal bloom outbreak. For algal bloom in March, there was a significant negative correlation between Chi. a concentration and velocity, while obvious relationships in Chi. a and pH or DO, indicating that velocity was an important factor for this bloom outbreak and pH, DO were sensitive factors caused by bloom. For algal bloom in May, there was a significant negative correlation between Chl. a concentration and velocity, while a significant positive correlation between Chli. a and flow quan-tity , and also obvious relationship in CM. a and pH, SD. It indicated that velocity and flow quantity were important factors for algal bloom outbreak in May, and pH, SD became the sensitive indices. According to the operational schedules of TGR, March and May belong to the period with high water level and discharge, respectively. Schedule times with different hydrodynamics may be respon-sible for the difference of effect factors on algal bloom, but the mechanism need to be further studied. Results suggested that the al-gal bloom mechanism in the different operational schedules of TGR is different from each other significantly. Therefore, the study on algal bloom in backwater region of Daning River need to be performed according to the operational schedule of TGR.