中文摘要：

城市湖泊是陆地水圈的重要组成部分,与人类活动关系极为密切。然而城市发展导致城市湖泊富营养化愈发严重,湖泊生态环境问题引起了广泛关注。本文研究了2012年至2013年间北京城区12个公园湖泊表层沉积物的有机氮同位素组成、碳氮比值、总有机氮和总有机碳含量的分布情况,探讨表层沉积物生产力状态、沉积物的有机质来源定性与定量分析、湖泊营养输入程度和过程等。研究表明,后海及群明湖等的有机碳、氮含量较其他公园湖泊的高,土壤和污水有机质等对湖泊沉积物的贡献突出,表明这些湖泊初级生产力及营养程度高,具有一定的富营养化风险;各个湖泊的分布位置、周围环境以及管理方式导致了其生产力、营养状况及有机质来源的差异,应该分别从控制水土流失、减少污水输入、及时清洁水面上的浮游植物与枯枝落叶等多方面着手进行,减少湖泊环境污染风险,保持湖泊环境生态平衡。本研究为了解城市湖泊环境有机质来源和过程、湖泊现代环境的管理和防治,提供可靠的研究方法和评价体系。

英文摘要：

As an important component of hydrosphere,urban lakes have the closest relationship with human activity. However,in recent years,lakes＇ ecological environment problems（ e.g. eutrophication） became more and more serious,especially in Beijing. This study analyzed organic nitrogen isotope composition,carbon and nitrogen ratios,total organic carbon and total organic nitrogen contents of sediment samples collected from 12 lakes in Beijing since 2012 to 2013,and discussed the ecological environment of these lakes from three aspects： The level of lake nutrient input,the productivity state of surficial sediments and the source of sediment organic matter. The results suggested that the Houhai Lake and the Qunming Lake have higher contents of carbon and nitrogen than other lakes,implying that these lakes have higher level of initial productivity and nutrition and stand a higher risk of eutrophication. The differences of productivity,nutritional status and organic matter source among these lakes were resulted from their geographical location,environment and management.In conclusion,this study suggested that controlling soil and water loss,restraining wastewater inputting,and cleaning the phytoplankton and litter on the surface of lakes are ways for reducing the pollution risk of and keeping the ecological balance of the lakes.