RAPID: Effect of massive, exceptional floods on sediment-associated isotope concentrations - implications for sediment source identification and erosion rate estimation

为应对2011年南部非洲前所未有的洪水，该快速项目将在纳米比亚最近搬运的河流沉积物在随后的雨季受到扰动之前，对这些沉积物的同位素浓度进行取样。随着2011年的“洪水记录”发生在过去14年中曾三次采样的大部分地区，该项目抓住了一个独特的机会来测试一个基本的根据现场铍-10浓度推断盆地规模侵蚀速率的基本假设（几乎未经检验）-给定位置的核素浓度随时间推移是一致的，即使在大洪水之后。 研究所还将测试从其他与沉积物有关的同位素（流星体10 Be、210 Pb和137 Cs）对沉积物来源的推断。了解河流沉积物中原位10 Be和大气10 Be，210 Pb和137 Cs浓度的时间变化，以及每个同位素系统如何响应大规模风暴事件，是负责任地应用这些同位素作为沉积物示踪剂和侵蚀速率监测器的先决条件。 与沉积物有关的同位素10 Be、210 Pb和137 Cs是流行的，并被广泛应用于这些目的，但它们的解释取决于给定位置的核素浓度是否随时间而一致。本项目将对这一关键假设进行测试。

In response to unprecedented 2011 floods in southern Africa, this RAPID project will sample isotope concentrations in recently transported fluvial sediments in Namibia before these sediments are disturbed in the subsequent rainy season. With the 2011 'flood of record' occurring over much of the area that has been sampled on three previous occasions in the past 14 years, this project seizes a unique opportunity to test a fundamental (and virtually untested) assumption underlying the inference of basin-scale erosion rates from in situ Berilium-10 concentrations--that nuclide concentrations at a given location are consistent over time, even after major flood events. The PIs will also test inferences made about sediment sources from other sediment-associated isotopes (meteoric 10Be, 210Pb and 137Cs). Understanding the temporal variability of in situ 10Be and meteoric 10Be, 210Pb, and 137Csconcentrations in river sediment, as well as how each isotopic system responds to massive stormevents, is a prerequisite to applying these isotopes responsibly as sediment tracers and erosion rate monitors. Sediment-associated isotopes of 10Be, 210Pb, and 137Cs are popular and widely applied for such purposes, yet their interpretation depends on whether or not nuclide concentrations are consistent over time at a given location. This project will provide a test of this key assumption.