以再生水补给的城市沟渠水生态系统构建与水质修复机制

The reclaimed water provided important water resources for the urban freshwater landscapes. The water quality severely degraded in the urban ditches because of the multiple high level nutrients and toxic pollutants. It is important to recover the water quality and re-built the healthy aquatic ecosystems based on the stream ecological theories. And it is necessary to compare mechanisms of aquatic ecosystem succession between the urban ditches and natural streams through the field monitoring. The aquatic ecosystem restoration and water quality recovering would follow the three steps: habitat restoration, aquatic ecosystem construction, and composition and process adjustment of the constructed ecosystems. By using the artificial channel, the succession of constructed aquatic communities would be monitored in simulating the natural stream characteristics.The efficiency and mechanisms of water quality recovery would be compared under different substrate composition, different water chemistry condition and hydrological variation in the artificial channel. The stability and efficiency of the constructed aquatic ecosystems would be studied under different complexity and biodiversity. Meanwhile, the environmental behaviors of persistent organic pollutants (POPs) would be studied within the aquatic ecosystem of the artificial channels. The working schemes of water quality recovery and healthy aquatic ecosystem construction would be provided for the urban ditches. The corresponding adjustment rules of systematic process for sustaining the healthy waterway would be submitted.

再生水已经成为我国城市景观水体重要补给。再生水中污染物组份复杂，城市沟渠水体黑臭现象频发。为有效维护和恢复城市沟渠水质，基于河流生态学理论开展城市沟渠水质修复，重建完善的水生态系统研究十分必要。本项目拟通过定期野外监测，阐明城市沟渠水生态系统演替规律及其与自然河流的差异。针对城市沟渠与自然河流在水质、生境和水文条件方面存在的显著特征差异，利用人工沟渠，按照"修复生境条件-恢复水生态系统-调控系统结构"的总体思路，研究环境条件差异、水生态系统多样性与复杂性对其演替特征和水质修复的影响，关注POPs污染物受人工水生态系统调控下的环境行为与规律。提出城市沟渠健康水生态系统构建方案，提出水生态系统结构优化与调控等一系列措施，为恢复健康的城市水体提供切实可行的依据。

再生水已经成为我国城市景观水体重要补给。再生水中污染物组份复杂，城市沟渠水体黑臭现象频发。为有效维护和恢复城市沟渠水质，基于河流生态学理论开展城市沟渠水质修复，开展完善沟渠河流水生态系统的研究十分必要。本项目以大型底栖动物为主要研究对象，通过定期野外监测和野外原位实验，阐明城市沟渠水生态系统演替规律及其与自然河流的差异特征。针对城市沟渠与自然河流在水质和生境方面存在的显著特征差异，利用人工沟渠，按照"修复生境条件-恢复水生态系统-调控系统结构"的总体思路，研究沟渠生态系统在环境条件差异、水生态系统多样性与复杂性对其演替特征和水质修复的影响，并关注POPs污染物受人工水生态系统调控下的环境行为与规律。主要结果显示：1）以再生水补给的北京市城市沟渠生态系统中，水体富营养化程度依然较高，大型底栖动物群落无法在现有富营养化状况下恢复到自然或近自然的状况，敏感物种较少，仅在一定程度上恢复了部分中度耐污物种，底栖动物的功能类群依然以倔穴生活的直接收集者为主，总体的生物多样性不高；2）水生植物群落可以有效恢复大型底栖动物的物种多样性，增加底栖动物功能群和生态类型，但水环境污染状况是影响底栖动物分布的关键要素，研究发现电导率、化学需氧量和氨氮与底栖动物多样性呈负相关，溶解氧与底栖动物多样性呈正相关；3）以再生水补给的城市河流中，水体中和水生生物体内均检出多种抗生素，北京市清河以喹诺酮类和大环内脂类抗生素为主，总含量（∑QNs和∑MCs）分别达到45.5-6089.6ng/L和5.2-1525.5ng/L，水生植物和水生动物均出现较明显的生物富集现象，植物中主要含有喹诺酮类和四环素类抗生素，最大含量分别达到99.7%和80.6%，动物体内主要是喹诺酮类抗生素，最高达97.1%，恩氟沙星在植物（最大值294182L/kg）和动物（最大值1127435.9L/kg）体内的生物富集指数都很高，总体认为以再生水补给的河流中抗生素污染比较严重，氧氟沙星、环丙沙星、诺氟沙星的危害系数>1，超过了该种抗生素环境风险值，应引起相关部门的重视。相关研究提出城市沟渠健康水生态系统的关键要素，提出水生态系统结构优化的主要途径，并为城市再生水补给的水生态修复和水安全管理提供了切实可行的依据。