In Northern France, land use is dominated by agriculture. Erosion by runoff results in heavy loss of fertile soil into surface waters. There is a need for cost‐effective tools to trace the sediment flux in catchments. This study highlights the potential of environmental magnetism to provide rapid non‐destructive parameters to characterize the spatiotemporal runoff versus bedload signal in a watershed. Between 2015 and 2017, within the Canche River watershed, several spatiotemporal sampling campaigns of suspended particulate matter (SPM) were undertaken and two distinct “snapshot campaigns” of flood events were conducted at key locations acquiring, in addition, hydrodynamical observations (discharge, turbidity, sediment load, etc.). Agricultural soils and SPM within the watershed have similar values for bulk magnetic concentration (isothermal remanent magnetization, IRM). The magnetic mineral assemblage of the SPM is dominated by soft ferromagnetic (sensu lato) minerals during low water conditions and is enriched in high‐coercivity phases during high water stages associated with rainfall events. Low‐temperature remanence experiments identified goethite and hematite as the high‐coercivity phases. IRM acquisition component analysis of the room temperature results quantify the relative input of high‐ versus low‐coercivity components focused on a given confluence site. Results from snapshot campaigns highlight the link between the enhanced runoff input of high‐coercivity particles during flood events and show that the S ratio parameter is an effective tool to trace erosion of topsoils.

中文翻译：

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土壤侵蚀背景下河流悬浮颗粒的磁性指纹图谱：以Canche河流域为例（法国北部）

在法国北部，土地使用以农业为主。径流侵蚀导致肥沃的土壤大量流失到地表水中。需要一种经济有效的工具来追踪流域内的沉积物通量。这项研究强调了环境磁化提供快速非破坏性参数来表征流域中时空径流与河床负荷信号的潜力。在2015年至2017年之间，在Canche河流域内，进行了数次悬浮颗粒物（SPM）的时空采样活动，并在关键位置进行了两次不同的洪水事件“快照活动”，此外还获得了水动力观测（流量，浊度） ，泥沙量等）。流域内的农业土壤和SPM的体磁浓度（等温剩余磁化强度，IRM）具有相似的值。SPM的磁性矿物组合主要由软铁磁（sensu lato）矿物在低水位条件下发生，并在与降雨事件相关的高水位阶段富含高矫顽力相。低温剩磁实验确定针铁矿和赤铁矿为高矫顽力相。室温结果的IRM采集成分分析可量化以给定汇合点为重点的高矫顽力成分和低矫顽力成分的相对输入。快照活动的结果突出显示了洪水事件期间高矫顽力颗粒的增强径流输入之间的联系，并表明S比参数是跟踪表层土壤侵蚀的有效工具。