Subsurface tile drainage is recognized as a significant source of sediment and particulate phosphorus (PP) in the midwestern U.S. However, the role of subsurface flow pathway and source water connectivity dynamics on sediment transport is poorly understood. The overarching objective of this study was to investigate sediment and PP loading dynamics for a midwestern subsurface tile drained agroecosystem and assess the governing flow pathway and water sources impacting subsurface sediment loads. In this study, we used a recently-developed framework that couples event-based hydrograph recession and specific conductance-end-member mixing analysis (SC-EMMA) to assess governing drivers of sediment transport through tile. We collected high-frequency specific conductance, turbidity, and subsurface discharge data from an edge-of-field (EOF) tile main located in northwestern Ohio for 15 months. Multiple linear regression (MLR) analysis and hysteresis analysis were employed to evaluate the impact of pathway-connectivity dynamics on flow-weighted mean Total Suspended Solids (TSS) concentrations. The MLR analysis showed that quickflow of new water (Q_quick-new) had the highest flow-weighted mean sediment concentrations, and that concentrations associated with quickflow of old water (i.e., matrix-macropore exchange) were variable. Analysis using the hysteresis index (HI) showed that hysteresis characteristics (magnitude and direction) for separated hydrographs using the pathway-connectivity framework deviated from HI values of subsurface discharge (Q_tile) and highlighted the importance of Q_quick-new through much of the monitoring period. For events immediately following tillage and cover crop application in Fall 2019, we found Q_quick-old was the primary form of preferential flow, peak sediment concentrations coincided with Q_quick-old, and event sediment loadings during these events decreased relative to the previous fall. The findings suggest that reducing preferential transport of new water may be an effective strategy for reducing sediment and particulate P loadings at the edge-of-field.

在美国中西部，地下瓦排水被认为是沉积物和颗粒磷 (PP) 的重要来源。然而，人们对地下流动路径和源水连通性动力学对沉积物迁移的作用知之甚少。本研究的首要目标是研究中西部地下瓦片排水农业生态系统的沉积物和 PP 负荷动态，并评估影响地下沉积物负荷的主导流动路径和水源。在这项研究中，我们使用了一个最近开发的框架，该框架将基于事件的水位线衰退和特定的电导端元混合分析 (SC-EMMA) 相结合，以评估通过瓷砖的泥沙运输的控制驱动因素。我们收集了高频比电导，位于俄亥俄州西北部的一个场边缘 (EOF) 瓦主管 15 个月的浊度和地下排放数据。采用多元线性回归 (MLR) 分析和滞后分析来评估通路连接动力学对流量加权平均总悬浮固体 (TSS) 浓度的影响。MLR分析表明，快速流动的新水（ Q _quick-new）具有最高的流量加权平均沉积物浓度，并且与快速流动的旧水（即基质-大孔交换）相关的浓度是可变的。使用滞后指数 (HI) 的分析表明，使用路径连通性框架分离的水文过程线的滞后特性（幅度和方向）偏离了地下放电的 HI 值（Q _tile ) 并在大部分监控期间强调了Q _{quick-new的重要性。}对于 2019 年秋季耕作和覆盖作物应用之后的事件，我们发现Q_快速老化是优先流的主要形式，峰值沉积物浓度与Q_快速老化一致，并且这些事件期间的事件沉积物负荷相对于上一个秋季有所下降. 研究结果表明，减少新水的优先输送可能是减少田边沉积物和颗粒 P 负荷的有效策略。