An important gap in the management of land erosion in mining-affected areas is the understanding of the entire sediment routing system and the links between sources and storage at the catchment scale. In this study, we examine sediment delivery and its seasonality in the nickel mining-affected Santa Cruz and Pamalabawan catchments in the Philippines. We monitored discharge, suspended sediment concentrations and suspended sediment loads across 13 sub-catchments with contrasting degrees of mining influence from June 2018 to July 2019. First, we show the importance of the size of the area that has been physically disturbed within our sub-catchments, with as little as 10–22% of relative disturbance area being enough to generate four-fold to eight-fold increase in the sediment yield relative to less disturbed and pristine areas. We found that sub-catchments with > 10% disturbance exhibit the highest sediment yields (15.5 ± 44.7 t km⁻² d⁻¹) compared with sub-catchments with < 10% disturbance (3.6 ± 17.7 t km⁻² d⁻¹) and undisturbed catchments (2.0 ± 5.7 t km⁻² d⁻¹). We also show that sediment flushing predominantly occurs in the most disturbed sub-catchments at the onset of the wet season. A small number of flood events transports the bulk of the sediment, with hysteresis effects being most pronounced in disturbed areas. Lastly, we show that floodplain sediment recycling exerts a key control on sediment delivery at both reach and catchment scales, with the relative contribution of floodplain sources to the sediment budget becoming dominant in the latter stages of the wet season- up to 89% of the total sediment export per storm event. This study highlights the importance of both degree of disturbance and sediment pathways in controlling sediment transport in mining-disturbed areas, and that considering the entire sediment routing system including intermediate stores is crucial to optimizing existing and future measures against siltation and potential contamination of trace metals and metalloids downstream of mining areas.

中文翻译：

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受镍矿开采影响的热带集水区的季节性通量和沉积物路径

受采矿影响地区土地侵蚀管理的一个重要差距是对整个沉积物路径系统以及流域尺度上源与存储之间的联系的理解。在这项研究中，我们研究了菲律宾受镍矿开采影响的 Santa Cruz 和 Pamalabawan 流域的沉积物输送及其季节性。从 2018 年 6 月到 2019 年 7 月，我们监测了 13 个受采矿影响程度不同的子流域的排放、悬浮泥沙浓度和悬浮泥沙负荷。首先，我们展示了我们子流域内受到物理干扰的区域大小的重要性。流域，相对干扰较少的原始区域，只要 10-22% 的相对干扰区域就足以使沉积物产量增加 4 到 8 倍。⁻² d ^-1 ) 与干扰 < 10% (3.6 ± 17.7 t km ^-2 d ^-1 ) 和未受干扰的集水区 (2.0 ± 5.7 t km ^-2 d ^{-1) 相比}）。我们还表明，泥沙冲刷主要发生在雨季开始时最受干扰的子流域。少数洪水事件运送了大部分沉积物，滞后效应在受干扰地区最为明显。最后，我们表明漫滩沉积物再循环对河段和流域尺度的沉积物输送发挥关键控制作用，在雨季后期，漫滩源对沉积物收支的相对贡献占主导地位 - 高达 89%每次风暴事件的总沉积物出口。本研究强调了扰动程度和沉积物路径在控制采矿干扰区沉积物输送方面的重要性，