作者：Feng, Y., Jiao, L., Wang, Y., He, J., Zhang, W. & Peng, F.

Dissolved organic matter (DOM) composition critically influences sediment nitrogen (N) cycling, yet the distinct roles of its hydrophilic (HIM) and hydrophobic (HOM) fractions remain incompletely characterized. Through controlled simulation experiments, we characterized the structural differences between HIM and HOM using techniques such as elemental analysis and electron paramagnetic resonance (EPR). By correlating these findings with quantitative monitoring of N fluxes in the overlying water column and key physicochemical parameters (pH and redox potential), we systematically evaluated the effects of HIM and HOM on N dynamics under natural, hypoxic, and alkaline hypoxic (pH similar to 10) conditions. Our results demonstrate that HIM markedly enhanced ammonium-N (NH4N) release, increasing fluxes by 60 % over controls (p < 0.001), with a further two-fold amplification under hypoxia. In contrast, HOM consistently yielded significantly lower NH4N fluxes compared to HIM across all conditions (p < 0.001). Under alkaline hypoxia, a universal suppression of NH4N release (50 % reduction) was observed, while HIM uniquely promoted nitrate-N (NO3N) flux, elevating it to a level significantly above that of all other treatments (p < 0.05). The differences in N dynamics at the sediment-water interface caused by HIM and HOM may be attributed to their distinct compositions. This study elucidated the mechanisms of DOM-mediated N release and transformation, providing a basis for mitigating lake eutrophication and advancing insights into the potential role of DOM in global carbon and N cycles.

溶解有机质（DOM）的组成对沉积物氮（N）循环具有关键影响，但其亲水组分（HIM）与疏水组分（HOM）的不同作用仍未被充分表征。研究通过受控模拟实验，利用元素分析与电子顺磁共振（EPR）等技术表征了HIM与HOM的结构差异；并将其与上覆水体中氮通量的定量监测及关键理化参数（pH与氧化还原电位）相关联，系统评估了HIM与HOM在自然、缺氧以及碱性缺氧（pH ≈ 10）三种条件下对氮动态的影响。结果表明：HIM显著促进铵态氮（NH₄⁺-N）的释放，通量较对照增加60%（p < 0.001），且在缺氧条件下进一步放大至两倍；相比之下，HOM在所有条件下均产生显著低于HIM的NH₄⁺-N通量（p < 0.001）。在碱性缺氧条件下，观察到NH₄⁺-N释放受到普遍抑制（降幅达50%）；而HIM则独特地促进了硝态氮（NO₃⁻-N）通量，使其显著高于其他所有处理（p < 0.05）。HIM与HOM在沉积物—水界面所致氮动态的差异，可能源于二者组成的差异。本研究阐明了DOM介导的氮释放与转化机制，为缓解湖泊富营养化提供了依据，并深化了对DOM在全球碳氮循环中潜在作用的认识。

（来源：Water Research 2026  DOI: 10.1016/j.watres.2026.125554）