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51.
Time variable Earth’s gravity field from SLR satellites 总被引:4,自引:4,他引:0
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Rolf?S.?ArvidsonEmail author Cornelius?Fischer Andreas?Luttge 《Aquatic Geochemistry》2015,21(5):415-422
We compare the canonical treatment of calcite’s dissolution rate from the literature in a closed system, particle batch reactor, with the alternative approach suggested by Truesdale (Aquat Geochem, 2015). We show that the decay of rate over time can be understood in terms of the evolution and distribution of reactive sites on the surface of these particles. We also emphasize that interpretation of observed rates must not exclude the fundamental role of crystal defects, whose importance is already implicitly reflected in the common form of rate laws in geochemistry. The empirical behavior of overall rate in closed systems, such as those described by Truesdale, may thus reflect relationships between defect centers and the generation of steps over the calcite surface (previously documented for silicates), such that below a critical free energy limit, there is insufficient driving force to open hollow cores and thus a loss of reaction mechanism. Dissolution in this very-near-equilibrium regime will be dependent on the distribution of extant steps and the energetics of new kink site nucleation. However, these sensitivities are complicated in the case of particle systems by grain boundaries, edges, corners, and other terminations. Such discontinuities constitute a defect class whose overall kinetic importance will be strongly tied to particle diameter and which can act independently of the internal strain field imposed by screw and edge dislocations. 相似文献
55.
Alexandre Badoux Jonas Witzig Peter F. Germann Hans Kienholz Peter Lüscher Rolf Weingartner Christoph Hegg 《水文研究》2006,20(2):377-394
This article describes an investigation on runoff generation at different scales in the forested catchment of the Sperbelgraben in the Emmental region (Swiss Prealps) where studies in the field of forest hydrology have a history of 100 years. It focuses on the analysis of soil profiles and the subsequent sprinkling experiments above them (1 m2), as well as on surface runoff measurements on larger plots (50 to 110 m2). In the Sperbelgraben investigation area, two very distinct runoff reactions could be observed. On the one hand, very high production of saturation overland flow was registered on wet areas of gleyic soils, with runoff coefficients between 0·39 and 0·94 for profile irrigation. On the other hand, almost no surface runoff was measured on Cambisols, with the exception at some sites of a hydrophobic reaction detected at the beginning of storms after dry periods (coefficients for profile irrigation: 0·01–0·16). This pattern was observed during 1 m2 soil plot irrigation and on surface runoff plots. Apart from a less distinctive signal of the water‐repellent litter layer on the larger surface runoff plots, the dominant hydrological processes at the two scales are the same. The determined runoff reaction at the two scales corresponds well with information from a forest site type map describing soil and vegetation characteristics and used as a substitute for a soil map in this study. Theoretical considerations describing forest influence on flood discharge are discussed and evaluated to be in good agreement with observations. These findings are a sound foundation for application in hydrological catchment modelling. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Allessandro Piccolo Riccardo Spaccini Rolf Nieder Joerg Richter 《Climatic change》2004,67(2-3):329-343
In a long-term (one year) experiment, a sandy Podzol and a silty-loamy Loess soil were treated with labile (polysaccharides, AG) and stable (mature compost, CMP, and two humic acids from compost, HAC, and lignite, HAL) organic matter and the organic carbon (OC) lost by mineralization was periodically evaluated. The stable materials alone induced a significant reduction of OC losses in Podzol CMP <, HAL, <, HAC, Control), whereas the same treatments, except for CMP, produced an OC loss larger than control in Loess. This was attributed to the diverse textural and physical status of the two soils. The added stable organic matter became protected in the Podzol soil within the aggregates formed by the interaction with the coarse inorganic phase, while it was more easily decomposed in the Loess soils due to the strength of the native humic-clay complexes. In both soils, when the stable organic materials were mixed with polysaccharides (AG), the OC losses from this labile fraction were significantly reduced, being CMP more OC sequestering than HAC and HAL, in the order. These results confirmed that labile organic matter in soils can be protected from biodegradation by repartition into the hydrophobic domains of the stable, humified organic matter. This study suggests that mature compost and humic acids may usefully integrate management practices aimed to sequester organic carbon in soils. 相似文献
58.
Challenges in global ballast water management 总被引:3,自引:0,他引:3
Endresen Ø Lee Behrens H Brynestad S Bjørn Andersen A Skjong R 《Marine pollution bulletin》2004,48(7-8):615-623
Ballast water management is a complex issue raising the challenge of merging international regulations, ship's specific configurations along with ecological conservation. This complexity is illustrated in this paper by considering ballast water volume, discharge frequency, ship safety and operational issues aligned with regional characteristics to address ecological risk for selected routes. A re-estimation of ballast water volumes gives a global annual level of 3500 Mton. Global ballast water volume discharged into open sea originating from ballast water exchange operations is estimated to approximately 2800 Mton. Risk based decision support systems coupled to databases for different ports and invasive species characteristics and distributions can allow for differentiated treatment levels while maintaining low risk levels. On certain routes, the risk is estimated to be unacceptable and some kind of ballast water treatment or management should be applied. 相似文献
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Olga V. Sidorova Matthias Saurer Vladimir S. Myglan Anja Eichler Margit Schwikowski Aleksander V. Kirdyanov Marina V. Bryukhanova Oksana V. Gerasimova Ivan A. Kalugin Andrey V. Daryin Rolf T. W. Siegwolf 《Climate Dynamics》2012,38(1-2):175-188
For the first time we present a multi-proxy data set for the Russian Altai, consisting of Siberian larch tree-ring width (TRW), latewood density (MXD), δ13C and δ18O in cellulose chronologies obtained for the period 1779–2007 and cell wall thickness (CWT) for 1900–2008. All of these parameters agree well between each other in the high-frequency variability, while the low-frequency climate information shows systematic differences. The correlation analysis with temperature and precipitation data from the closest weather station and gridded data revealed that annual TRW, MXD, CWT, and δ13C data contain a strong summer temperature signal, while δ18O in cellulose represents a mixed summer and winter temperature and precipitation signal. The temperature and precipitation reconstructions from the Belukha ice core and Teletskoe lake sediments were used to investigate the correspondence of different independent proxies. Low frequency patterns in TRW and δ13C chronologies are consistent with temperature reconstructions from nearby Belukha ice core and Teletskoe lake sediments showing a pronounced warming trend in the last century. Their combination could be used for the regional temperature reconstruction. The long-term δ18O trend agrees with the precipitation reconstruction from the Teletskoe lake sediment indicating more humid conditions during the twentieth century. Therefore, these two proxies could be combined for the precipitation reconstruction. 相似文献