河流-地下水侧向交互带氮的生物地球化学行为及其环境效应

The hyporheic zone is a special hydrogeological body with strong interaction between surface water and groundwater in biogeochemical activities, which is one of the hot topics in hydrogeology field in recent years. At present, the research of interaction zone at home and abroad is mostly concentrated on the vertical exchange of the bottom of the river bed, and not enough attention is paid to the study of the lateral subsurface flow exchange in the river bed, especially for the lack of systematic study on the lateral biogeochemistry and microbial community interaction on nitrogen transformation mechanism between river and groundwater. This project focused on the process of nitrogen biogeochemical transformation in the lateral interaction zone of river and groundwater in arid and semi-arid areas, which would take GuanZhong reach of Weihe River as a typical research area. We adopted high-resolution in-situ monitoring, environmental isotope tracing, laboratory experiments, molecular biology technology and geochemical simulation, and illuminated the spatio-temporal evolution of hydrodynamics and hydrochemistry and the response characteristics of microbial communities, we also studied on the interaction and competition mechanism of nitrification, denitrification, dissimilation reduction (DNRA) and anaerobic ammonium oxidation in the in-situ environment, and revealed the influence mechanism and environmental effects of river - groundwater interaction which effect on the biogeochemical process of nitrogen, to deepen the understanding of the migration and transformation of nitrogen in the river - groundwater interaction zone. It is of great scientific and practical value to improve the level of comprehensive prevention and control of nitrogen pollution in water body.

地表水与地下水交互带是生物地球化学活动强烈的独特水文地质体，是近年来水文地质领域研究的热点之一。目前国内外对交互带研究还多集中于河床底部的垂向交换，对于河床侧向潜流交换研究关注不够，特别是对侧向上河流与地下水相互作用过程中氮的生物地球化学行为及微生物群落响应机制缺乏系统研究。本项目聚焦于干旱半干旱区河水-地下水侧向交互带氮生物地球化学作用过程，以渭河关中段为典型研究区，采用高分辨率原位监测、环境同位素示踪、室内实验、分子生物学技术和地球化学模拟等手段，阐明交互带水动力-水化学时空演化规律及微生物群落的响应特征，研究原位环境下硝化、反硝化、异化还原（DNRA）、厌氧氨氧化等转化过程的相互作用和竞争机制，揭示河水-地下水相互作用对氮生物地球化学过程的影响机理及其环境效应，深化河流-地下水交互带氮迁移转化规律的认识，对于提升水体氮污染综合防治水平，具有重要的科学意义和实际价值。

河流-地下水侧向交互带是控制河岸与河流物质循环及能量流动的重要场所，具有复杂的河水-地下水交互机制和物理化学特征，准确地刻画侧向交互带的生物地球化学过程对改善水环境质量和维持水生态系统稳定有着十分重要的作用。本项目基于高分辨率原位监测、环境同位素示踪、分子生物学技术和地球化学模拟等手段，深入开展了干旱半干旱区河流-地下水侧向交互带氮的生物地球化学化学行为及其环境效应研究。重要成果如下：（1）揭示了河流-地下水侧向交互带水动力场、水化学场及微生物场的演化规律，计算了河流-地下水侧向交互带的水交换量（0.003-0.18m3/m2/d），阐明了侧向交互带水文地球化学演化机理；（2）估算了河流-地下水侧向交互带中氮的转化速率（0.84-35.19 μmol·N2·kg-1·h-1），识别了氮的迁移转化过程与主控因素；（3）解析了水动力驱动下交互带氮的主要循环过程及微生物优势菌的响应关系与氮污染物的自然衰减能力，揭示了氮生物地球化学过程与水动力变化的耦合机制，初步构建了干旱半干旱区河流-地下水系统交互带水动力-水化学-微生物协同运移及演化的理论与方法体系。上述研究成果提高了对河流—地下水交互带的氮迁移转化过程与生态效应的认知水平，为建立描述交互带关键水文-生物地球化学过程耦合的精细化模型提供了理论依据及技术支持。