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The effect of calcium on synthetic glass alteration mechanisms has been studied. It is known that the higher the calcium content in the glass, the higher the forward rate. However, in a confined medium reaching apparent saturation state and a pH90°C around 9, synthetic calcium-bearing glasses are those with the lowest alteration rates. This work brings new and fundamental evidence toward understanding the alteration mechanisms: the rate-decreasing effect of calcium exists even if the calcium comes from the solution. Calcium from solution reacts with silica network in the hydrated layer at the glass surface. The calcium effect on the alteration kinetics is explained by the condensation of a passivating reactive interphase (PRI) whose passivating properties are strongly enhanced when calcium participates in its construction. These experiments provide new evidence of the role of condensation mechanisms in glass alteration. This better understanding of the calcium effect on glass long-term behavior will be useful both for improving glass formulations and for understanding the influence of the water composition. 相似文献
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Christophe Bouvier Marko Adamovic Pierre-Alain Ayral Pascal Brunet Jean-François Didon-Lescot Jean-Marc Domergue Rosario Spinelli 《水文研究》2021,35(4):e14144
This study focuses on a 10-m2 plot within a granitic hillslope in Cevennes mountainous area in France, in order to study infiltration and subsurface hydrological processes during heavy rainfalls and flash floods. The monitoring device included water content at several depths (0–70 cm for the shallow soil water; 0–10 m for the deep water) during both intense artificial and natural rainfall events, chemical and physical tracers, time-lapse electrical resistivity tomography. During the most intense events, the infiltrated water was estimated to be some hundreds of millimetres, which largely exceeds the topsoil capacity (≤40 cm deep in most of the cases). The weathered/fractured rock area below the soil clearly has an active role in the water storage and sub-surface flow dynamics. Vertical flow was dominant in the first 0–10 m, and lateral flow was effective at 8–10 m depth, at the top of the saturated area. The speed of the vertical flow was estimated between 1 and 10 m/hr, whereas it was estimated between 0.1 and 1 m/hr for the lateral flow. The interpretation of the experiments might lead to a local pattern of the 2D-hydrological processes and profile properties, which could be generic for most of the mountainous catchments under Mediterranean climate. It suggests that fast triggering of floods at the catchment scale cannot be explained by a mass transfer within the hillslope, but should be due to a pressure wave propagation through the bedrock fractures, which allows exfiltration of the water downstream the hillslope. 相似文献
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Luc Neppel Benjamin Renard Michel Lang Pierre-Alain Ayral Denis Coeur Eric Gaume 《水文科学杂志》2013,58(2):192-208
Abstract Flood frequency analysis based on a set of systematic data and a set of historical floods is applied to several Mediterranean catchments. After identification and collection of data on historical floods, several hydraulic models were constructed to account for geomorphological changes. Recent and historical rating curves were constructed and applied to reconstruct flood discharge series, together with their uncertainty. This uncertainty stems from two types of error: (a) random errors related to the water-level readings; and (b) systematic errors related to over- or under-estimation of the rating curve. A Bayesian frequency analysis is performed to take both sources of uncertainty into account. It is shown that the uncertainty affecting discharges should be carefully evaluated and taken into account in the flood frequency analysis, as it can increase the quantiles confidence interval. The quantiles are found to be consistent with those obtained with empirical methods, for two out of four of the catchments. Citation Neppel, L., Renard, B., Lang, M., Ayral, P.-A., Coeur, D., Gaume, E., Jacob, N., Payrastre, O., Pobanz, K. & Vinet, F. (2010) Flood frequency analysis using historical data: accounting for random and systematic errors. Hydrol. Sci. J. 55(2), 192–208. 相似文献
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