三峡水库运行对近坝区水质时空变化的影响分析

Effects of Three Gorges Reservoir operation on spatiotemporal variation of water quality near the dam

为探究三峡水库运行对近坝区水质时空变化特征的影响,运用主成分分析和方差分析等方法分析2015-2019年近坝区的溶解氧(DO)、pH值、化学需氧量(COD)、五日生化需氧量(BOD_(5))、氨氮(NH_(3)-N)、总磷(TP)、总氮(TN)、粪大肠杆菌(FC)等8个水质参数,分析不同运行期水质变化特征.结果表明,近坝水域水质全年达到Ⅲ类及以上标准;高水位时期和消落期影响水质的主要参数为DO,坝上低水位和蓄水期影响水质的主要参数为TP和FC,坝下低水位期影响水质的主要参数为COD,NH_(3)-N,FC,TN,蓄水期为TN,TP,BOD_(5),NH_(3)-N,COD和FC.TN,TP,FC近5年来显著下降,但坝下NH_(3)-N质量浓度有升高趋势.控制三峡水库流域内农业面源污染,提高近坝区域城镇污水收集处理率,加大船舶污染治理,是改善近坝区水质的重要措施.

In order to explore the spatiotemporal variation of water quality and the effects of the dam operation on the water quality near Three Gorges Dam,principal component analysis(PCA)and variance analysis were used to study the water quality characteristic near the dam from 2015 to 2019,including dissolved oxygen(DO),pH,chemical oxygen demand(COD),biochemical oxygen demand(BOD_(5)),ammonia(NH_(3)-N),total phosphorus(TP),total nitrogen(TN)and fecal coliforms(FC).The results showed that the water quality near the dam reached or above classⅢstandard.The main parameter affecting water quality was DO in high water level period and water releasing period.In the reservoir the dominant parameter affecting water quality were TP and FC in the low water level and impounding period.While in the downstream of the dam the dominant factor affecting water quality were COD,NH_(3)-N,FC and TN in the low water level period,TN,TP,BOD_(5),NH_(3)-N,COD and FC in the impounding period.TN,TP and FC concentration decreased significantly in recent 5 years,but NH_(3)-N concentration in the downstream of the dam showed an increasing trend.Controlling agricultural non-point source pollution in the three Gorges Reservoir basin,increasing the rate of urban sewage collection and treatment near the dam area,and strengthening pollution control from ships are important measures to improve the water quality near the dam.