大型人工湿地生态可持续性评价

大型人工湿地现已广泛应用于湖滨带、河滨带水质净化及湿地生态修复,这些人工湿地的生态可持续性评价对于其科学管理调控及长期可持续运行具有重要意义。运用综合指标评价及层次分析法,根据人工湿地生态系统的特点,提出并建立了适合评价人工湿地可持续性运行的指标体系,建立的评价指标包括生态特征与功能、水质净化功能及经济社会功能三项一级指标,及对应的14个二级指标。运用建立的评价指标体系对南四湖湖滨带新薛河大型人工湿地示范工程的生态可持续性运行了评价,评价结果显示:植物多样性、氨氮去除能力、生物入侵抵抗力、野生动物栖息地、COD去除能力是影响大型人工湿地运行效果的主要制约因素;新薛河人工湿地生态可持续性综合指数为0.6862,处于"良"级,其中生态特征功能可持续性指数最高,为0.7732;水质净化功能和社会经济功能指数分别为0.6190,0.6492。由结果可知,南四湖新薛河大型人工湿地具有重要的生态修复功能,水质净化功能方面应加强植物定期收割及植被管理,同时经济社会功能还有待加强,植物经济效益及旅游娱乐效益还有待深入开发。建立的人工湿地可持续性运行的评价指标体系具有较强的针对性,可用于其他大型人工湿地的生态可持续性评价。

Evaluation of ecosystem sustainability for large-scale constructed wetlands

Constructed wetlands,as an ecological restoration technology,have been widely applied to deal with the degradation of natural wetlands and the pollution of water bodies,and more attention should be focused on the system stability and maintenance of functions over the long term.A Comprehensive Index System can be applied to perform an overall evaluation of an ecosystem through many different indices from different aspects and the Analytic Hierarchy Process is a structured technique for organizing and analyzing complex decisions particularly in group decision making.Based on the Comprehensive Index System and Analytic Hierarchy Process,we presented a measure method to evaluate the eco-sustainability of large-scale constructed wetlands,which are constructed for water purification and offsetting the degradation of natural wetlands.The index system contains three criteria: ecological structures and functions,water purification capability,and economic-social functions,and then fourteen sub-criteria including biodiversity,primary production,resistance to ecological invasion,wildlife habitats provision,COD removal,ammonia nitrogen removal,total nitrogen removal,total phosphorus removal,siltation,wetland plants harvest,operation costs,wetland plants benefits,recreation benefits and public awareness of the value of the wetlands.The weight of each criterion and sub-criterion is determined by the results of expert questionnaires.Five levels including "very good","good","average","bad" and "very bad" are established to determine the sustainability of constructed wetland with the listed continuity intervals 1.0—0.8,0.8—0.6,0.6—0.4,0.4—0.2,0.2—0.0].A case study based on the index system was conducted in a five-stage surface-flow constructed wetland,which was built in the Xinxue River estuary by Nansi Lake to improve the water quality and to make up for the degradation of riparian wetlands.The calculated results of the weight of each criterion and sub criterion showed that "ecological structures and functions" and "water purification capability" account for 40.17% and 42.94% of the weight respectively,while biodiversity,ammonia nitrogen removal,resistance to ecological invasion,wildlife habitats provision,and COD removal are the main factors in the sub-criteria influencing the sustainability of the Xinxue River constructed wetland.According to the eco-sustainability evaluation,the eco-sustainability of the Xinxue River constructed wetland is at a ’good’ level(0.6862) on the whole,and specifically the ecological structure and functions(0.7732),water purification capability(0.6190) and social-economic functions(0.6492) are all at a ’good’ level,although the biodiversity index is 0.5200,which means the biodiversity of the Xinxue River constructed wetland is still lower than that of the natural wetland surrounding Nansi Lake,which also reflects the conflicts between ecosystem functions and structures in constructed wetlands.The index of benefits from the wetland plants is also in a "bad" level because the annual biomass of Xinxue River constructed wetland is kept in the wetland according to the local laws and regulations instead of being developed into commercial products.In conclusion,the further improvement for Xinxue River constructed wetland should focus on the extension of economic and social functions: development of wetland ecotourism should be exploited and the technological innovations of wetland plants processing should be enhanced to promote sustainable development of the local economy.The index system suggested here can also be adopted to evaluate other similar large-scale constructed wetlands.