Riverine sediments play an important role in the healthy functioning of river ecosystems as they provide nutrients and a connectivity signal throughout the catchment sediment cascade. However, excess sediment supply to rivers can have several detrimental impacts on water quality, availability and ecology. The application of catchment management practices requires a comprehensive understanding of both spatial and temporal sediment dynamics to tackle point and diffuse river pollution. While the sources, pathways and fate of eroded sediment in river systems have been widely studied, temporal dynamics have received less attention, mainly due to the complexity of the processes and the lack of methods available to assess these dynamics. This contribution reviews the application of Fallout Radionuclides (FRNs) as sediment residence time tracers. We explore their suitability as sediment chronometers in rivers, the relevance of sediment residence time to sediment budgeting, and discuss the current models that have been employed to determine sediment residence time in river systems. Our review also identifies the challenges, opportunities and the future research needs for a comprehensive application of FRNs to evaluate sediment residence time. In evaluating approaches to sediment residence time, we have summarised several pitfalls requiring consideration and identified avenues for further research. For instance, attention should be given to sorption behaviour when using ⁷Be and ¹³⁷Cs as residence time tracers in rivers under changing environmental conditions; particle size effects; activity concentration dilution by mixing of newly tagged ⁷Be sediment with ⁷Be-poor sediment from older or different sources; source controls on ⁷Be delivery to rivers; and the influence of direct fallout into stream channels. Finally, further research is needed to assess the influence of environmental and anthropogenic factors on sediment residence time such as land use, topography, flow regimes, soil type, soil erosion measures and climate change, all of which have important implications from a catchment management perspective.

河流沉积物在河流生态系统的健康运作中发挥着重要作用，因为它们在整个集水区沉积物级联中提供营养和连通性信号。然而，河流的过量沉积物供应会对水质、可用性和生态产生若干不利影响。流域管理实践的应用需要全面了解时空沉积物动态，以解决点状和扩散性河流污染。虽然河流系统中侵蚀沉积物的来源、路径和归宿已被广泛研究，但时间动态受到的关注较少，主要是由于过程的复杂性以及缺乏评估这些动态的方法。这篇文章回顾了辐射放射性核素的应用（FRN）作为沉积物停留时间示踪剂。我们探讨了它们作为河流沉积物计时器的适用性、沉积物停留时间与沉积物预算的相关性，并讨论了目前用于确定河流系统中沉积物停留时间的模型。我们的审查还确定了全面应用 FRN 来评估沉积物停留时间的挑战、机遇和未来的研究需求。在评估沉积物停留时间的方法时，我们总结了几个需要考虑的陷阱，并确定了进一步研究的途径。例如，使用⁷Be 和¹³⁷Cs 作为环境条件变化下河流中的停留时间示踪剂；粒度效应；^{通过将新标记的7} Be 沉积物与来自较旧或不同来源的⁷ Be 贫乏沉积物混合来稀释活性浓度；^对7 Be 输送到河流的源头控制；以及直接辐射到河流渠道的影响。最后，需要进一步研究评估环境和人为因素对沉积物停留时间的影响，例如土地利用、地形、流态、土壤类型、土壤侵蚀措施和气候变化，所有这些都从流域管理的角度具有重要意义.