城市静态小水体生态修复措施与生态服务价值评估研究

城市静态小水体污染是城市环境污染的重要问题之一。针对城市静态小水体的特点,依据稳态转换理论和生物操纵理论,形成适应于城市静态小水体的生态修复措施,并运用于武汉市青山区倒口湖水生态修复工程。工程实施后湖水水质得到明显改善,其中,水体透明度由0.2~0.4m提高至1.0~1.5m,溶解氧浓度由1.82~2.35mg/L上升至5.21~6.28mg/L,CODMn浓度由14.96~16.3mg/L降低至3.56~5.01mg/L,TN浓度由2.61~2.99mg/L降至1.27~1.6mg/L,TP浓度由0.43~0.62mg/L降至0.06~0.12mg/L。进一步对倒口湖水生态系统的供给、调节、文化以及支持4方面的服务价值进行评估,通过对水生态系统服务价值评价指标计算得出,工程实施前后水生态系统服务价值分别为299.34万元和645.62万元,新增服务价值346.28万元。在增量价值中固碳释氧、净化水质指标占比最大,表明在水生系统动植物的协同作用下,倒口湖的水质条件得到明显改善。

Assessment of an Ecosystem Restoration Project and Evaluation of Ecosystem Services for a Small Urban Lake in Wuhan, China

Pollution of small urban lakes is an important issue in urban environments. Daokou Lake is located in the Qingshan District of Wuhan City and, after sediment dredging and a water connection project in 2016, has a water area of 28814 m2. Surface runoff is the primary source of water for Daokou Lake, resulting in high turbidity and problematic hydrodynamics. In this study we assessed an ecological restoration project on Daokou Lake that was developed based on the characteristics of the lake, regime shift theory and biomanipulation. The project involved controlling exogenous and endogenous pollution, improving the hydrodynamics, restoring the ecosystem and a plan for effective long-term management. The project began in August 2018 and was completed in July 2019, with continuing follow-up inspections. Water quality parameters were monitored before and after the project and included Secchi depth water clarity (SD), dissolved oxygen (DO), chemical oxygen demand (CODMn), total nitrogen (TN) and total phosphorus (TP). Water quality in Daokou Lake improved significantly after the project; SD increased from 0.2-0.4 m to 1.0-1.5 m, DO increased from 1.82-2.35 mg/L to 5.21-6.28 mg/L, CODMn decreased from 14.96-16.3 mg/L to 3.56-5.01 mg/L, TN decreased from 2.61-2.99 mg/L to 1.27-1.6 mg/L and TP decreased from 0.43-0.62 mg/L to 0.06-0.12 mg/L. The improvement in water quality was attributed to the synergistic action of the plants and animals in Daokou Lake in response to pollution reduction. The ecosystem services provided by Daokou Lake were also evaluated, including water supply and regulation, cultural value and ecological services (fixing carbon, supplying oxygen and purifying water). The estimated value of ecosystem services was 2.99 million yuan before the project and 6.45 million yuan after the project, an increase of 3.46 million yuan. Carbon fixation and water purification accounted for the largest proportion of the ecosystem service value. The Daokou Lake project significantly improved water quality while more than doubling the value of ecosystem services.