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121.
Catchments as reactors: a comprehensive approach for water fluxes and solute turnover 总被引:1,自引:1,他引:0
Peter Grathwohl Hermann Rügner Thomas Wöhling Karsten Osenbrück Marc Schwientek Sebastian Gayler Ute Wollschläger Benny Selle Marion Pause Jens-Olaf Delfs Matthias Grzeschik Ulrich Weller Martin Ivanov Olaf A. Cirpka Ulrich Maier Bertram Kuch Wolfgang Nowak Volker Wulfmeyer Kirsten Warrach-Sagi Thilo Streck Sabine Attinger Lars Bilke Peter Dietrich Jan H. Fleckenstein Thomas Kalbacher Olaf Kolditz Karsten Rink Luis Samaniego Hans-Jörg Vogel Ulrike Werban Georg Teutsch 《Environmental Earth Sciences》2013,69(2):317-333
Sustainable water quality management requires a profound understanding of water fluxes (precipitation, run-off, recharge, etc.) and solute turnover such as retention, reaction, transformation, etc. at the catchment or landscape scale. The Water and Earth System Science competence cluster (WESS, http://www.wess.info/) aims at a holistic analysis of the water cycle coupled to reactive solute transport, including soil–plant–atmosphere and groundwater–surface water interactions. To facilitate exploring the impact of land-use and climate changes on water cycling and water quality, special emphasis is placed on feedbacks between the atmosphere, the land surface, and the subsurface. A major challenge lies in bridging the scales in monitoring and modeling of surface/subsurface versus atmospheric processes. The field work follows the approach of contrasting catchments, i.e. neighboring watersheds with different land use or similar watersheds with different climate. This paper introduces the featured catchments and explains methodologies of WESS by selected examples. 相似文献
122.
Suprathermal proton bremsstrahlung (SPB) of energetic protons is an important source of high-energy X-ray and gamma-ray photons
in the interstellar medium. We calculate the suprathermal bremsstrahlung radiation power and the associated energy loss rate
of the radiating protons. Also the mean photon energy from the SPB process is derived which can be used to construct a monochromatic
approximation of the radiation power. The SPB power is the starting point for the quantitative modelling of theoretical SPB
radiation spectra in cosmic sources.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
123.
Paul F. Schuster Michael M. Reddy James W. LaBaugh Renee S. Parkhurst Donald O. Rosenberry Thomas C. Winter Ronald C. Antweiler Walter E. Dean 《水文研究》2003,17(4):823-838
Williams Lake, Minnesota is a closed‐basin lake that is a flow‐through system with respect to ground water. Ground‐water input represents half of the annual water input and most of the chemical input to the lake. Chemical budgets indicate that the lake is a sink for calcium, yet surficial sediments contain little calcium carbonate. Sediment pore‐water samplers (peepers) were used to characterize solute fluxes at the lake‐water–ground‐water interface in the littoral zone and resolve the apparent disparity between the chemical budget and sediment data. Pore‐water depth profiles of the stable isotopes δ18O and δ2H were non‐linear where ground water seeped into the lake, with a sharp transition from lake‐water values to ground‐water values in the top 10 cm of sediment. These data indicate that advective inflow to the lake is the primary mechanism for solute flux from ground water. Linear interstitial velocities determined from δ2H profiles (316 to 528 cm/yr) were consistent with velocities determined independently from water budget data and sediment porosity (366 cm/yr). Stable isotope profiles were generally linear where water flowed out of the lake into ground water. However, calcium profiles were not linear in the same area and varied in response to input of calcium carbonate from the littoral zone and subsequent dissolution. The comparison of pore‐water calcium profiles to pore‐water stable isotope profiles indicate calcium is not conservative. Based on the previous understanding that 40–50 % of the calcium in Williams Lake is retained, the pore‐water profiles indicate aquatic plants in the littoral zone are recycling the retained portion of calcium. The difference between the pore‐water depth profiles of calcium and δ18O and δ2H demonstrate the importance of using stable isotopes to evaluate flow direction and source through the lake‐water–ground‐water interface and evaluate mechanisms controlling the chemical balance of lakes. Published in 2003 by John Wiley & Sons, Ltd. 相似文献
124.
125.
Mathematical Geosciences - 相似文献
126.
Alexis Nutz Jean‐François Ghienne Mathieu Schuster Raphaël Certain Nicolas Robin Claude Roquin Olivier Raynal Frédéric Bouchette Philippe Duringer Pierre A. Cousineau 《Boreas: An International Journal of Quaternary Research》2014,43(2):309-329
The stratigraphy of the last deglaciation sequence is investigated in Lake Saint‐Jean (Québec Province, Canada) based on 300 km of echo‐sounder two dimensional seismic profiles. The sedimentary archive of this basin is documented from the Late Pleistocene Laurentidian ice‐front recession to the present‐day situation. Ten seismic units have been identified that reflect spatio‐temporal variations in depositional processes characterizing different periods of the Saint‐Jean basin evolution. During the postglacial marine flooding, a high deposition rate of mud settling, from proglacial glacimarine and then prodeltaic plumes in the Laflamme Gulf, produced an extensive, up to 50 m thick mud sheet draping the isostatically depressed marine basin floor. Subsequently, a closing of the water body due to glacio‐isostatic rebound occurred at 8.5 cal. ka BP, drastically modifying the hydrodynamics. Hyperpycnal flows appeared because fresh lake water replaced dense marine water. River sediments were transferred towards the deeper part of the lake into river‐related sediment drifts and confined lobes. The closing of the water body is also marked by the onset of a wind‐driven internal circulation associating coastal hydrodynamics and bottom currents with sedimentary features including shoreface deposits, sediment drifts and a prograding shelf‐type body. The fingerprints of a forced regression are well expressed by mouth‐bar systems and by the shoreface–shelf system, the latter unexpected in such a lacustrine setting. In both cases, a regressive surface of lacustrine erosion (RSLE) has been identified, separating sandy mouth‐bar from glaciomarine to prodeltaic muds, and sandy shoreface wedges from the heterolithic shelf‐type body, respectively. The Lake Saint‐Jean record is an example of a regressive succession driven by a glacio‐isostatic rebound and showing the transition from late‐glacial to post‐glacial depositional systems. 相似文献
127.
Ute Mann Jochen Knies Shyam Chand Wilfried Jokat Ruediger Stein Janine Zweigel 《Marine and Petroleum Geology》2009,26(8):1624-1639
With the recently recovered organic-rich sediments of early Tertiary age from the Lomonosov Ridge by the Integrated Ocean Drilling Program (IODP) Expedition 302, the first data collection directly from source rocks of the central basins of the Arctic Ocean is now available. Using the results of seismic interpretations and published sedimentological and organic geochemical data from Expedition 302, the framework for the first quantitative assessment of source-rock quality and distribution of the Palaeogene sediments was modelled in the central Arctic Ocean. The modelling results suggest that an approximately 100-m-thick Early to Middle Eocene sedimentary sequence of good to very good source rocks exists along a 75 km long transect across the Lomonosov Ridge. In-situ generation of hydrocarbons is unlikely because the overburden (200–250 m) and consequently the thermal maturity are too low. Burial history and thermal modelling reveal that an additional overburden of at least 1000 m is necessary to start hydrocarbon generation along the ridge. However, source-rock modelling results show that good source-rock potential may exist in correlative units in the adjacent Amundsen Basin. Simulated organic carbon contents of 1.5–5%, coupled with an overburden of 1000–1200 m, and heat flow anomalies (117 and 100 mW m−2) due to the vicinity to the Gakkel Ridge spreading centre indicate that necessary conditions for hydrocarbon expulsion are already reached, and point to viability of a potential petroleum system. Our results support the hypothesis that deposition of a potentially good hydrocarbon source rock occurred across the entire Arctic Basin and adjacent margins during the early Tertiary. 相似文献
128.
Seismic time‐lapse surveys are susceptible to repeatability errors due to varying environmental conditions. To mitigate this problem, we propose the use of interferometric least‐squares migration to estimate the migration images for the baseline and monitor surveys. Here, a known reflector is used as the reference reflector for interferometric least‐squares migration, and the data are approximately redatumed to this reference reflector before imaging. This virtual redatuming mitigates the repeatability errors in the time‐lapse migration image. Results with synthetic and field data show that interferometric least‐squares migration can sometimes reduce or eliminate artifacts caused by non‐repeatability in time‐lapse surveys and provide a high‐resolution estimate of the time‐lapse change in the reservoir. 相似文献
129.
The theory and practice of multisource full‐waveform inversion of marine supergathers are described with a frequency‐selection strategy. The key enabling property of frequency selection is that it eliminates the crosstalk among sources, thus overcoming the aperture mismatch of marine multisource inversion. Tests on multisource full‐waveform inversion of synthetic marine data and also the Gulf of Mexico data show speedups of 4 × and 8 × , respectively, compared with conventional full‐waveform inversion. 相似文献
130.
David Kaeter Martin A. Ziemann Ute Böttger Iris Weber Lutz Hecht Sergey A. Voropaev Alexander V. Korochantsev Andrey V. Kocherov 《Meteoritics & planetary science》2018,53(3):416-432
We present results of petrographic, mineralogical, and chemical investigations of three Chelyabinsk meteorite fragments. Three distinct lithologies were identified: light S3 LL5, dark S4–S5 LL5 material, and opaque fine-grained former impact melt. Olivine–spinel thermometry revealed an equilibration temperature of 703 ± 23 °C for the light lithology. All plagioclase seems to be secondary, showing neither shock-induced fractures nor sulfide-metal veinlets. Feldspathic glass can be observed showing features of extensive melting and, in the dark lithology, as maskelynite, lacking melt features and retaining grain boundaries of former plagioclase. Olivine of the dark lithology shows planar deformation features. Impact melt is dominated by Mg-rich olivine and resembles whole-rock melt. Melt veins (<2 mm) are connected to narrower veinlets. Melt vein textures are similar to pegmatite textures showing chilled margins, a zone of inward-grown elongated crystals and central vugs, suggesting crystallization from supercooled melt. Sulfide-metal droplets indicate liquid immiscibility of both silicate and sulfide as well as sulfide and metal melts. Impact melting may have been an important factor for differentiation of primitive planetary bodies. Graphite associated with micrometer-sized melt inclusions in primary olivine was detected by Raman mapping. Carbon isotopic studies of graphite could be applied to test a possible presolar origin. 相似文献