Dissolved organic matter (DOM) entering the river networks affects aquatic ecosystems, yet it remains difficult to quantify the strength of various environmental factors in controlling reach-scale uptake and transport of DOM. This study combined reach-scale field experiments and stochastic modeling to investigate the uptake and transport dynamics of natural fluorescent DOM (FDOM) in a forested coastal plain stream located in the southeastern U.S. FDOM from litter leachate and sodium chloride (NaCl) were injected into the stream under base flow conditions (with different flow rates) on three separate occasions over a 3-month period. Field measurements showed that FDOM and NaCl exhibited different anomalous dynamics characterized by the peak and tailing behaviors of concentration breakthrough curves (BTC), indicating that the transport of FDOM was regulated more by physical retention and/or biogeochemical recycling than that of NaCl. The preferential removal of humic fluorescence than protein fluorescence before the BTC peak suggests that physical sorption was more important than biological degradation in early FDOM removal at the field site. A tempered fractional advection–dispersion-reaction model (TFADRM) was proposed to describe the FDOM migration process and estimate the FDOM spiraling metrics, and the resultant metrics were compared to those from conventionally used BTC-integrated approach. Results revealed that solute retention can lower the peak concentration and enhance the late-time tail of the FDOM BTC, whereas irreversible biogeochemical reaction processes can consume FDOM and decrease the BTC peak. Relative to the commonly used OTIS model, TFADRM can better capture the observed BTC late-time tail by considering multiple rates for the mass exchange/uptake of FDOM in streams, and therefore, this study provided a more reasonable estimate of FDOM spiraling metrics and transport dynamics at the reach scale.

进入河流网络的溶解有机物 (DOM) 会影响水生生态系统，但仍然难以量化各种环境因素在控制 DOM 的范围内吸收和运输方面的强度。本研究结合了河段尺度的现场实验和随机建模，以研究位于美国东南部森林覆盖的沿海平原溪流中自然荧光 DOM (FDOM) 的吸收和传输动态，来自垃圾渗滤液和氯化钠 (NaCl) 的 FDOM 被注入到在 3 个月的时间里，在三个不同的场合，在基本流量条件下（具有不同的流速）的流。现场测量表明，FDOM 和 NaCl 表现出不同的异常动力学特征，其特征是浓度突破曲线 (BTC) 的峰值和拖尾行为，表明与 NaCl 相比，FDOM 的运输更多地受物理保留和/或生物地球化学循环的调节。在 BTC 峰之前优先去除腐殖质荧光而不是蛋白质荧光表明物理吸附比现场现场早期 FDOM 去除中的生物降解更重要。提出了一种缓和分数平流-弥散-反应模型 (TFADRM) 来描述 FDOM 迁移过程并估计 FDOM 螺旋指标，并将所得指标与传统使用的 BTC 集成方法的指标进行比较。结果表明，溶质保留可以降低 FDOM BTC 的峰值浓度并增强后期拖尾，而不可逆的生物地球化学反应过程会消耗 FDOM 并降低 BTC 峰值。