城市湖泊水体修复过程的富营养化评价--以武汉南湖为例

Eutrophication evaluation and treatment suggestions for urban lake water ecological restoration--South Lake in Wuhan

人类活动对城市湖泊生态系统影响强烈,从2020年4月至11月对武汉南湖开展了水质监测,通过数据比较,阐述了南湖生态修复期间水质的时空变化与发展趋势,并对南湖富营养化水平进行了综合评价.结果表明,南湖富营养化状况总体呈好转趋势,湖区水体恢复了一定的自净能力,部分水质指标得到改善,但总氮(TN)和总磷(TP)质量浓度超标严重,最大值分别为9.85 mg/L和1.49 mg/L,叶绿素a(Chl.a)质量浓度居高不下,平均质量浓度为51.85μg/L,蓝藻水华状况仍然十分严重.在时间尺度上,南湖水体的综合营养状态指数(TLI)虽然呈下降趋势,但总体仍为中度富营养化状态;在空间尺度上,南湖各湖湾表现出明显的区域异质性,具体水质状况为大南湖优于华农湾,小南湖最差.小南湖外源污染比较严重,是南湖今后治理的重点,应加强对污染排口的处理,拓展水生植物种植区域,开展蓝藻水华应急处置.

Human activities have a strong impact on urban lake ecosystem.The water quality of the South Lake in Wuhan was monitored for 8 months(from April 2020 to November 2020).Compared with the data of previous years,the temporal and spatial variations and development trends of water quality during the recent ecological restoration of South Lake were clarified,and the eutrophication levels were comprehensively evaluated.The results showed that some water quality indexes of the South Lake were partly promoted,but the total nitrogen(TN)and total phosphorus(TP)exceeded the standard severely,with the highest concentration of 9.85 mg/L and 1.49 mg/L.The chlorophyll a(Chl.a)density remained high,and the average concentration reached to 51.85μg/L,which made the cyanobacteria water bloom becoming a very serious problem.On the temporal scale,the comprehensive nutrient index(TLI)of South Lake was gradually decreasing,but it still remained to a moderate eutrophication state.On the spatial scale,regional heterogeneity was appeared obviously in each bay of South Lake,and the water quality of Danan Lake is better than Huanong Bay,and Xiaonan Lake is the worst.The eutrophication status in South Lake is correlated with regional outlet pollution to a certain extent,and expost treatment in South Lake will focus on the exogenous pollution in Xiaonan Lake.In the future,it will play an important role in improving the water quality of South Lake by the integrated measures of strengthening the outlets management and controlling the cyanobacteria water-bloom scale,enlarging hydrophytes demonstration areas.