三峡水库消落带景观基塘系统对地表径流氮磷拦截效益——以重庆开州区汉丰湖为例

Nitrogen and Phosphorus Removal Efficiency of Urban Landscape Dike-Pond System for surface flows in the Riparian Zone of Three Gorges Reservoir——A Case Study on Hanfeng Lake in Kaizhou District of Chongqing

生态工程是解决消落带生态环境问题行之有效的手段,景观基塘系统是消落带生态工程的有益探索,科学评估该系统对地表径流氮磷拦截效益是当前研究的重要内容。选择开州区汉丰湖南岸石龙船大桥段串联型景观基塘系统,开展为期2年,23场自然降雨期间地表径流氮、磷营养盐含量的监测。结果表明,开州区城市地表径流氮污染较重,磷污染略轻;景观基塘系统对城市地表径流氮磷削减效果较好,其对TN、NO_3^--N、NH_4^+-N、TON及TIN等削减率分别为44%、44%、38%、62%和30%,对TP、DTP、PO_4^(3-)-P及颗粒态磷的削减率为37%、34%、32%和70%;景观基塘系统主要通过沉积、过滤、拦截颗粒态和非溶解性污染物实现对氮、磷等污染物的削减,受到初始污染浓度和降雨强度影响显著;2015年系统污染拦截效率显著高于2014年,随时间推移,系统稳定性提高。本研究认为景观基塘系统在城市与河湖水体间构建了一道有效的纳污屏障,对汉丰湖水环境保护具有重要意义,可作为三峡库区面源污染防控的重要技术手段。

Ecological engineering is effective to solve the ecotope problems caused in water-level-fluctuating zone. Landscape dike-pond system(LDPS), as an innovative ecological engineering, has been designed and demonstrated in drawdown zone of Three Gorges Reservoir for ecological restoration and non-point source pollution control. In this study, a tandem LDPS tem located in the Hanfeng Lake in Kaizhou was selected to perform a2-year investigation on the nitrogen and phosphorus removal efficiency of such ecological engineering for surface flows during a total of 23 rainfall events. The results indicate that the urban surface runoff was characterized by higher nitrogen loading but lower phosphorus loading. LDPS could observably reduce the nitrogen concentration in the runoff, with the removal rates of 44%, 44%, 38%, 62% and 30% for TN, NO_3^--N, NH_4^+-N, TON and TIN,respectively. Phosphorus concentrations in runoff through the LDPS were also reduced significantly, with TP, DTP,PO_4^(3-)-P and particulate phosphorus(PP) being reduced by 37%, 34%, 32% and 70%, respectively. Particulate andundissolved N or P were predominated components that can be intercepted easily by the LDPS. The nitrogen and phosphorus removal efficiencies of such system in 2015 were much higher than those in 2014, indicating that the system could be more stable over time. This study suggests that the LDPS can act as an effectively ecological method to control the non-point source pollution in urban, especially in the Riparian Zone of Three Gorges Reservoir.