Abstract：
Biogeochemical hot spots play a crucial role in the cycling and transport of redox-sensitive elements (RSEs) in the hyporheic zone (HZ). However, the transformation mechanisms of RSEs and patterns of RSEs hot spots in the HZ remain poorly understood. In this study, hydrochemistry and multi-isotope (N/C/S/O) datasets were collected to investigate the transformation mechanisms of RSEs, and explore the distribution characteristics of RSEs transformation hot spots. The results showed that spatial variability in key drivers was evident, while temporal change in RSEs concentration was not significant, except for dissolved organic carbon. Bacterial sulfate reduction (BSR) was the primary biogeochemical process for sulfate and occurred throughout the area. Ammonium enrichment was mainly caused by the mineralization of nitrogenous organic matter and anthropogenic inputs, with adsorption serving as the primary attenuation mechanism. Carbon dynamics were influenced by various biogeochemical processes, with dissolved organic carbon mainly derived from C3 plants and dissolved inorganic carbon from weathering of carbonate rocks and decomposition of organic matter. The peak contribution of dissolved organic carbon decomposition to the DIC pool was 46.44 %. The concentration thresholds for the ammonium enrichment and BSR hot spots were identified as 1.5 mg/L and 8.84 mg/L, respectively. The distribution pattern of RSEs hot spots was closely related to the hydrogeological conditions. Our findings reveal the complex evolution mechanisms and hot spots distribution characteristics of RSEs in the HZ, providing a basis for the safe utilization and protection of groundwater resources.
摘要：
生物地球化学热点在氧化还原敏感元素（RSE）的循环和运输中起着至关重要的作用。然而,HZ中RSE热点的转化机制和模式仍然知之甚少。在这项研究中,收集水化学和多同位素（N/C/S/O）数据集以研究RSE的转化机制，探索RSEs转化热点的分布特征。结果表明，关键驱动因素的空间变异性很明显，而RSEs浓度的时间变化不显著，除了溶解的有机碳。细菌硫酸盐还原（BSR）是硫酸盐的主要生物地球化学过程，并在整个地区发生。铵富集主要是由含氮有机质的矿化和人为输入引起的，以吸附为主要衰减机制。碳动力学受到各种生物地球化学过程的影响，溶解的有机碳主要来自C3植物，溶解的无机碳来自碳酸盐岩的风化和有机物的分解。溶解有机碳分解对DIC池的峰值贡献为46.44%。铵富集热点和BSR热点的浓度阈值分别为1.5mg/L和8.84mg/L,分别。RSEs热点的分布格局与水文地质条件密切相关。我们的发现揭示了HZ地区RSEs的复杂演化机制和热点分布特征，为地下水资源的安全利用和保护提供依据。
