查干湖富营养化发生机制及水量-水质模拟研究

Lake eutrophication seriously affects the quality of the water ecological system and the safety of drinking water. For the problem that the eutrophication mechanisms of shallow lake in previous researches are still unclear, which leads to poor practicality of research findings, this study comprehensively use field monitoring, laboratory simulation and model prediction to clarify the eutrophication mechanisms in shallow lake and predict the evolution trend of water environment under the background of extending paddy field. We Take Chagan Lake, a typical shallow lake in Songyuan irrigation area, as object. Firstly, the water environmental characteristics of Chagan Lake, water quantity and quality of farmland drainage are analyzed through macroscopic investigation and dynamic monitoring, the main limiting factors affecting eutrophication will be selected, the spatial-temporal distribution characteristics of drainage water from irrigation area will be analyzed, and the contribution to water eutrophication from extraneous P input will be quantitatively estimated. Then microscopic experiments are applied to study the effects of different environmental gradients on sediment phosphorus release rate, assess the potential risk of phosphorus release from the surficial sediments, and reveal the contribution to water eutrophication from internal sediment phosphorus release. Secondly the spatial-temporal distribution of plankton’s structure, abundance and biomass and its multiple relationships with water environmental factors will be analyzed to explore the seasonal succession patterns of the dominant populations and reveal the ecological effect of the changing water environment. On this basis, water quantity-WASP model will finally be constructed and predict the evolution trend of water environment under different coupling situations with different quantity and quality from farmland drainage in Chagan lake. The research will give control suggestions to eutrophic shallow lakes in irrigation area, Northeastern China and provide scientific support for the strategy formulation of lake ecosystem protection and recovery.

湖泊富营养化严重影响水生态系统质量和饮用水安全，针对以往研究中浅水湖泊富营养化发生机制不清晰、导致研究成果实用性差的问题，综合利用野外监测、室内分析、模型模拟等手段，阐明浅水湖泊富营养化的发生机制，预测农田开发下湖泊水环境的演变趋势。本研究以松原灌区查干湖为对象，首先开展查干湖水环境特征和农田退水水量水质的宏观调查与动态监测，筛选影响湖泊富营养化的主要限制因子，分析农田退水中营养盐的时空分布特征，探明外源输入对富营养化的贡献；然后通过微观实验研究不同环境梯度对底泥磷释放速率的影响，评估底泥磷释放风险，揭示内源磷释放对富营养化的贡献；在此基础上，构建水量—WASP水质模型，模拟预测不同农田退水水量和水质耦合情境下查干湖水环境的演变趋势。通过本研究为东北灌区浅水型湖泊富营养化的防治提出分时段、分区域的治理建议，对浅水湖泊水生态的保护和恢复策略的制定提供科学依据。

在全球环境变化及人类活动剧烈影响背景下，湖泊富营养化已经严重影响到水生态系统的质量和饮用水的安全，富营养化发生机制的研究对于湖泊水环境的治理至关重要。查干湖湿地是松原灌区的主要承泄区之一，同时还是吉林西部重要的生态屏障，对于防治吉林西部土地沙化、碱化、荒漠化具有重要意义。.本项目以内源氮磷释放-外源农田退水输入关系为切入点，开展查干湖水环境特征的宏观调查与动态监测、底泥沉积物中氮磷的空间分布及分层研究，田块尺度农田氮磷流失实验、底泥磷释放模拟研究、构建水量-WASP水质模型，取得以下进展：1）查干湖水环境特征：2018年查干湖水质为Ⅳ类，2019年为Ⅴ类，主成分分析显示2018年查干湖呈现出有机和氮磷污染型，2019年表现为氮磷污染。2）外源农田退水输入查干湖的氮磷负荷分别为TN约203.19t，TP约23.12t，其中前郭灌区农田退水携带TN 含量95.37t，TP约8.02t，大安灌区退水携带TN约102.2t，TP约14.4t，深重涝区排水携带TN5.62t，TP约0.7t。通过降水进入查干湖的TN约4719kg，TP约157kg。3）农田退水农田退水可以降低查干湖的盐度和碱度和总磷水平，查干湖呈以磷为限制的富营养化状态。查干湖内源负荷形成机制主导了湖水水化学环境和水质状况。4）2019年度田块尺度实验发现TN、TP的流失量分别为1.27kg/hm2、0.09kg/hm2，推算松原灌区水田的氮磷流失量分别为57.36t、4.07t。5）查干湖底泥TN含量在84.4-2362 mg/kg之间，底泥总磷含量在357.4- 678.2 mg/kg之间，磷的稳定持有量也随着随P的投加量增大而增大，吸持率f在0.89~0.96之间。本项目的执行，有助于完善东北灌区浅水型湖泊富营养化的发生机制，对于农田开发背景下评估承泄区湖泊水生态的保护和恢复策略具有一定的理论和实践意义。