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Abstract: Knowledge of the weathering processes controlling continental transfer of dissolved silicon (DSi) to the ocean is fundamental to the estimate of the long-term atmospheric CO2-budget. Studies at the soil profile and catchment scales demonstrate that the Si isotopic composition of soil and riverine DSi is a marker of abiotic and/or biotic weathering processes. In this paper, we first review Si isotopic fractionation in the natural environment. We then evaluate the application of Si isotopes to gain new insights into weathering processes on distinct spatial and temporal scales. We suggest that bulk soil δ30Si is inversely correlated to weathering degree, regardless of variability in climate, soil age and lithology. We also posit that the Si isotopic composition of DSi and suspended matter in rivers is indicative of the weathering regime (weathering- vs. transport-limited) prevailing in the area where DSi flux originates. Finally, we propose some future research directions. [Copyright &y& Elsevier]

Abstract: The present study aims to establish a simple mechanistic model for river bank erosion. Recent experiments demonstrate that small-scale laminar flumes can develop erosion structures similar to those encountered in Nature. From the Saint-Venant Equations, a classical sediment transport law and a simple avalanche model, it is shown that bank failure caused by flow erosion can be represented through simple boundary conditions. These conditions are able to deal with the water level adjustment imposed by a constant water outflow condition. Finally, they are implemented to approach numerically the widening of a laminar river. [Copyright &y& Elsevier]

Abstract: We discuss the present-day sediment transport by rivers, and hence the erosion rate in upstream basins, based on the example of Taiwan Rivers where large datasets are available. After data correction, the values of the suspended sediment load in the lower Kaoping River are nearly three times smaller than those from the literature. On the other hand, we add the bed load evaluated from numerical modelling, despite limitations from data and models. Whereas the contribution of the chemical denudation rate in Taiwan is minor, the bed load is significant and must be evaluated. We point out that biases in data collection may favour high values of suspended load data, and that large series of datasets are needed to reduce uncertainties and smooth the time variability effect. To cite this article: F.-C. Li et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]

In situ-produced cosmogenic nuclides provide a means for quantitative evaluation of a wide range of weathering and sediment transport processes. Although these nuclides have received attention for their power as geochronometers of surface exposure, it may be argued that they are more broadly suited for study of surface processes. In many environments, they may be used to evaluate collapse, erosion, burial, bioturbation, and creep, as well as providing a qualitative basis for distinguishing allochthonous from autochthonous materials. In addition, these nuclides can provide quantitative information on rates of erosion on scales of landforms and drainage basins. Here, we review the systematics of cosmogenic nuclide production within the Earth''s surface, and present field examples demonstrating the utilization of in situ-produced cosmogenic nuclides distributions for evaluation of a range of soil evolution processes. To cite this article: E.T. Brown et al., C. R. Geoscience 335 (2003). [Copyright &y& Elsevier]