Nitrate has been recognized as a global threat to environmental health. In this regard, the hyporheic zone (saturated media beneath and adjacent to the stream bed) plays a crucial role in attenuating groundwater nitrate, prior to discharge into surface water. While different nitrate removal pathways have been investigated over recent decades, the adsorption capacity of hyporheic sediments under natural conditions has not yet been identified. In this study, the natural attenuation capacity of the hyporheic-sediments of the Ghezel-Ozan River, located in the north-west of Iran, was determined. The sampled sediments (from 1 m below the stream bed) were characterized via XRD, FT-IR, BET, SEM, BJH, and Zeta potential. Nitrate adsorption was evaluated using a batch experiment with hyporheic pore-water from each study site. The study was performed in the hyporheic sediments of two morphologically different zones, including Z₁ located in the parafluvial zone having the clay sediment texture (57.8% clay) with smectite/Illite mixed layer clay type and Z₂ located in the river confluence area containing silty clay sediment texture (47.6% clay) with smectite/kaolinite mixed layer clay type. Data obtained from the batch experiment were subjected to pseudo-first order, pseudo-second order, intra-particle diffusion, and Elovich mass transfer kinetic models to characterize the nitrate adsorption mechanism. Furthermore, to replicate nitrate removal efficiencies of the hyporheic sediments under natural conditions, the sampled hyporheic pore-waters were applied as initial solutions to run the batch experiment. The results of the artificial nitrate solution correlated well with pseudo-second order (R²>95%; in both Z₁ and Z₂) and maximum removal efficiencies of 85.3% and 71.2% (adsorbent dosage 90 g/L, pH=5.5, initial adsorbate concentration of 90mg/L) were achieved in Z₁ and Z₂, respectively. The results of the nitrate adsorption analysis revealed that the nitrate removal efficiencies varied from 17.24±1.86% in Z₁ during the wet season to 28.13±0.89% in Z₂ during the dry season. The results obtained by this study yielded strong evidence of the potential of hyporheic sediments to remove nitrate from an aqueous environment with great efficiency.

硝酸盐已被公认为对环境健康的全球威胁。在这方面，流变带（流床下方和附近的饱和介质）在将地下水硝酸盐排放到地表水中之前起着至关重要的作用。尽管近几十年来研究了不同的硝酸盐去除途径，但尚未确定自然条件下流变沉积物的吸附能力。在这项研究中，确定了位于伊朗西北部的盖泽尔-奥赞河的流变沉积物的自然衰减能力。通过XRD，FT-IR，BET，SEM，BJH和Zeta电位对采样的沉积物（从流床下方1 m开始）进行表征。使用批量实验从每个研究地点对低渗孔隙水进行硝酸盐吸附评估。₁位于河流旁带，具有粘土沉积质地（57.8％粘土），具有蒙脱石/伊利石混合层粘土类型，Z ₂位于河流汇合区，含粉质粘土沉积质地（47.6％粘土），具有蒙脱石/高岭土混合层粘土类型。将从批处理实验中获得的数据进行伪一级，伪二级，粒子内扩散和Elovich传质动力学模型，以表征硝酸盐的吸附机理。此外，为了复制自然条件下流变沉积物的硝酸盐去除效率，将采样的流变孔隙水作为初始溶液进行批处理实验。人工硝酸盐溶液的结果与伪二级（R ²> 95％；在两个z ₁和Z ₂的85.3％和71.2％（吸附剂用量为90g / L，pH值= 5.5Hz，90毫克/升的初始浓度吸附））和最大去除率分别沿Z达到₁和Z ₂分别。硝酸盐吸附分析的结果表明，硝态氮的去除效率从湿季的Z _1的17.24±1.86％到旱季的Z _2的28.13±0.89％不等。这项研究获得的结果提供了有力的证据，表明流变沉积物具有从水环境中高效去除硝酸盐的潜力。