强烈水动力扰动下潜流带硝酸盐还原的时空演变规律与控制机理

潜流带对河流硝酸盐污染具有天然截留作用，明确潜流带硝酸盐迁移转化机制可为流域水环境管理提供科学依据。水库调节、傍河抽水等人类活动导致潜流带受到频繁强烈的水动力扰动，天然氧化还原分带特征随之改变，为硝酸盐还原与其他氧化还原敏感性元素循环（如铁）的相互作用提供条件。但以往对潜流带硝酸盐还原的研究大多只关注反硝化过程，忽略了水动力扰动和氧化还原带变化对硝酸盐还原路径和热点的影响。本项目结合批实验、15N示踪、柱实验和槽实验、数值模拟等方法，探索水动力模式和介质性质对潜流带氧化还原分带特征的影响规律，识别硝酸盐还原的不同路径和影响因素，建立耦合氧化还原分带信息的硝酸盐迁移转化新模型，揭示强烈水动力条件驱动下硝酸盐还原热点的时空演变规律和控制机理。本研究对于准确量化流域氮循环、维护河流生态系统持续稳定发展具有重要理论意义。

The hyporheic zone has natural interception effect on river nitrate pollution. Figuring out the mechanism of nitrate migration and transformation in the hyporheic zone could provide scientific basis for water environment management. Human activities such as reservoir regulation and river-side pumping lead to frequent and intense hydrodynamic disturbances in the hyporheic zone, and the characteristics of natural redox zones change accordingly, providing conditions for the interaction of nitrate reduction with other redox-sensitive elements cycling (such as iron). Previous studies on nitrate reduction in the hyporheic zone mainly focused on denitrification process, ignoring the influence of hydrodynamic disturbance and redox zone changes on the pathways and hot spots of nitrate reduction. Methods of batch experiment, sand column experiment, sandbox experiment, 15N isotopic tracer and numerical simulation will be applied for the following purpose: (i) exploring the influence of hydrodynamic patterns and aquifer properties on the characteristics of redox zones in hyporheic zone, (ii) identifying different pathways and influencing factors of nitrate reduction, (iii) developing a new numerical model of nitrate transport and transformation coupled with redox zone information, (iv) revealing the spatiotemporal evolution and control mechanism of nitrate reduction hot spots driven by strong hydrodynamic conditions. This study is of great theoretical significance to accurately quantify the nitrogen cycle and maintain the sustainable and stable development of river ecosystem.