洱海湖周农田浅层地下水位升降对土-水界面磷素迁移转化的影响机理

洱海湖周农田土壤剖面-浅层地下水界面是磷从土壤圈向水圈迁移的过渡地带，地下水位浅且大的季节性波动加速了土壤剖面中磷的形态变化及向地下水中迁移，严重威胁着湖周地下水及洱海的水质安全。本项目以洱海湖周河湖相沉积物和第四纪风化物发育的不同土壤（水稻土、红壤）为研究对象，通过浅层地下水升降的模拟试验和野外监测，研究不同种植类型（蔬菜、稻豆轮作）农田浅层地下水升降过程中土壤剖面和地下水中各形态磷的变化、分布及其相互关系，揭示浅层地下水升降引起的土壤理化特性和磷细菌变化对土壤剖面-地下水界面磷素迁移转化的作用机理，定量化确定土壤剖面-地下水界面磷的交换通量，阐明土壤剖面-地下水界面磷素的源汇转换机制。本研究将为减少农田土壤磷流失，降低洱海湖周浅层地下水磷污染，保护洱海水质安全提供科学支撑。

The soil profile-shallow groundwater interface in farmland around the Erhai Lake is a transition zone from the pedosphere to the hydrosphere. Shallower and larger seasonal fluctuations of groundwater tables accelerate the changes of phosphorus forms in the soil profile and their migration into groundwater, which will be serious threats to the water quality of Erhai Lake and groundwater of its surroundings. In this project, we will focus on different soils (paddy soil and red soil) developed on river-lacustrine facies deposits and quaternary red clay to study variations, distributions, and relationships of various forms of phosphorus in the soil profile and groundwater in the process of shallow groundwater fluctuation in farmland with different planting types (vegetable, rice and bean rotation) around the Erhai Lake by the simulated tests and the field monitoring of shallow groundwater fluctuation. The action mechanism of soil physical and chemical characteristics and changes of phosphorus bacteria caused by shallow groundwater fluctuation on phosphorus migration and transformation in the soil profile - groundwater interface will be revealed. The exchange flux of phosphorus between the soil profile and groundwater will be quantitatively determined. The source-sink conversion mechanism of phosphorus in soil profile-groundwater interface will be explained. This result can provide scientific support for reducing phosphorus loss in farmland soils, reducing phosphorus pollution in shallow groundwater around the Erhai Lake, and protecting the quality of Erhai Lake.