北京永定河河岸带生态修复对河流水质的影响

Effects of ecological restoration of riparian zone on water quality of Yongding river in Beijing

为探讨河岸带生态修复措施对河流水质的直接影响,以永定河已修复的门城湖—莲石湖区段为研究对象,于2013年7—10月沿西岸选取8个采样点,测定溶解氧(DO)、氨氮(NH+4—N)、硝氮(NO-3—N)和总磷(TP)的质量浓度.结果表明,河流DO浓度和各营养物质浓度均有明显的季节变化.大部分采样点的DO、NH+4—N和TP浓度未达到地表水IV类水体标准.水生植物较多的河岸带处,河流NH+4—N浓度较低.在生长旺季,长势好的水生植物越多,河流DO和NO-3—N浓度越高,TP浓度越低;在生长末期,枯落物较多的河岸带处,河流DO浓度较低,TP浓度较高.凸岸处的河流DO和NO-3—N浓度较高,而NH+4—N浓度较低.因此,改变护岸类型、水生植物的多度及河岸的弯曲程度等河岸带结构特征可引起河流水质的变化.

The ecological effects of restoration of flood lands and buffers from Mencheng lake to Lianshi lake along Yongding river in Beijing were discussed. From July to October in 2013,water samples were periodically collected at the 8 selected sites along the west bank, and the concentrations of dissolved oxygen（ DO）,nitrate nitrogen（ NO3^-—N）,ammonia nitrogen（ NH4^＋—N）,and total phosphorus（ TP） were measured and analyzed. The results showed that there were obvious seasonal variations in the concentrations of these nutrients and DO in Yongding river. For most of the sites,water quality could not meet the requirements for the surface water standard class IV. The NH4^＋—N concentration was low where the amount of hydrophytes was relatively large.During the growing season,higher coverage of hydrophytes led to higher DO and NO3^-— N concentrations and lower TP concentration,while at the end of the growing period,much small contributions to the higher TP and lower DO concentrations. The convex river bank could enhance the DO and NO3^-—N concentrations and reduce the NH4^＋—N concentration. In short,changes in the structure characteristics of riparian zone such as bank material,abundance of hydrophytes,and curvilinearity of banks had great effects on water quality in Yongding river.