坡耕地薄层紫色土-岩石系统中氮磷的迁移特征

于2015年两场代表性降雨事件下研究了紫色土坡耕地(1 500 m~2)水文过程驱动的氮磷地表和地下迁移特征.结果表明:(1)前期土壤水饱和度和降雨量决定地表径流和裂隙潜流的产流深度和胶体浓度的基本水平;降雨强度则控制产流量的变化趋势和胶体浓度的峰值水平.(2)氮素主要以溶解态随裂隙潜流迁移;磷素则主要以细颗粒结合态通过地表径流流失.(3)氮磷迁移过程的水文驱动特征明显,氮素迁移主要受裂隙潜流的驱动作用影响,而磷素迁移则主要受地表径流的驱动作用影响.该研究结果丰富了对坡耕地薄层土壤-裂隙母岩二元系统中氮磷迁移对降雨响应规律的认识,可为农业氮磷非点源污染防治提供可靠的田间数据支持并明确关键的水文调控环节.

Transport of Nitrogen and Phosphorus from Sloping Farmland with Thin Purple Soil Overlying Rocks

In a sloping farmland plot(1500 m²) of purple soil with underlying fractured mudrock in Southwest China, field monitoring and sampling campaigns were undertaken to explore the mechanisms of surface and subsurface transport of nitrogen and phosphorus upon two representative rain events in the summer of 2015. The results indicated that:1depths of surface runoff and subsurface fracture flow as well as average colloid export flux were dependent on antecedent soil wetness and rainfall amount, while discharge dynamics and colloid peak concentration were determined by rainfall intensity; 2nitrogen export was mainly in dissolved forms through subsurface fracture flow, however, phosphorus was mainly transported in particle-associated forms through surface runoff; 3the transport of nitrogen and phosphorus was strongly influenced by hydrological processes, with nitrogen and phosphorus transport being controlled by fracture flow and surface runoff, respectively. Our findings contribute significantly to the knowledge of nitrogen and phosphorus export from sloping farmland with thin soil underlain by fractured rock upon rainfall, and on the other hand this study provides reliable field data in support of developing effective approaches for controlling agricultural non-point source pollution of N and P and identifying key hydrological processes to be manipulated.