Ion association and hydration in 3:2 electrolyte solutions by dielectric spectroscopy: Aluminum sulfate     

Simon Schrödle  Wolfram W. Rudolph  Richard Buchner 《Geochimica et cosmochimica acta》2007,71(22):5287-5300

Broadband dielectric measurements utilizing state-of-the-art coaxial reflectometry and traveling-wave interferometry have been made on aqueous solutions of the 3:2 electrolyte aluminum sulfate at 25 °C over the frequency range 0.2 ? ν (GHz) ? 89 and at total solute concentrations 0.012 ? c (M) ? 0.65. Detailed analysis of the solute contribution to the dielectric spectra revealed the simultaneous presence of double solvent-separated (2SIP), solvent-shared (SIP) and contact (CIP) ion pairs. Concentrations of the various ion-pair types and the equilibrium constants for their formation were determined using calculated dipole moments and other relevant quantities. The 2SIPs and SIPs were found to persist down to low concentrations in this notionally strong electrolyte. Good agreement was found with earlier Raman and NMR studies for CIP concentrations and with thermodynamic determinations of the overall ion association constant. In contrast to divalent metal sulfate solutions, both SIPs and, to a lesser extent, 2SIPs remain present at quite high Al₂(SO₄)₃(aq) concentrations. The persistence of SIPs and 2SIPs was consistent with the effective hydration numbers obtained from an analysis of the cooperative H-bond relaxation mode of bulk water in the solutions. This analysis indicated that the hydration of Al³⁺ ions is extremely strong, with significant effects on the dielectric relaxation timescale even beyond the second hydration shell, at least in dilute solutions.  相似文献   

On interpreting hydrological change from regional climate models     

L. Phil Graham  Stefan Hagemann  Simon Jaun  Martin Beniston 《Climatic change》2007,81(1):97-122

Although representation of hydrology is included in all regional climate models (RCMs), the utility of hydrological results from RCMs varies considerably from model to model. Studies to evaluate and compare the hydrological components of a suite of RCMs and their use in assessing hydrological impacts from future climate change were carried out over Europe. This included using different methods to transfer RCM runoff directly to river discharge and coupling different RCMs to offline hydrological models using different methods to transfer the climate change signal between models. The work focused on drainage areas to the Baltic Basin, the Bothnian Bay Basin and the Rhine Basin. A total of 20 anthropogenic climate change scenario simulations from 11 different RCMs were used. One conclusion is that choice of GCM (global climate model) has a larger impact on projected hydrological change than either selection of emissions scenario or RCM used for downscaling.  相似文献   

Capillary collapse of loose pyroclastic unsaturated sands characterized at grain scale     

Mariagiovanna Moscariello  Sabatino Cuomo  Simon Salager 《Acta Geotechnica》2018,13(1):117-133

The reduction in volume for unsaturated soils wetted at constant total stress is indicated as capillary collapse. Several studies conducted on standard laboratory specimens (macro-scale) outlined the role of initial void ratio, confining pressure and matric suction on collapse onset. Conversely, few observations were made at grain scale, although an important influence of soil structure has been supposed since years. This paper investigated the collapse of coarse and fine sands derived from a pyroclastic soil of Southern Italy. The X-ray computed tomography was used to identify the mechanisms acting at grain scale and to measure the local variations of soil structure. The experimental procedure consisted in preparing remoulded unsaturated specimens and reducing the matric suction until the collapse occurred under self-weight. At different stages of the process, the sample was imaged by X-ray tomography. The experimental results provided original insight into: (1) transformation of soil structure during the wetting tests; (2) variation of porosity, water content and degree of saturation for the whole specimen; and (3) local variations of those variables in several representative sub-volumes. It is worth noting that collapse of coarse sand specimen occurred before saturation. This was also emphasized by the presence of macro-voids at collapse.  相似文献   

Using an integrated method for the determination of environmental TCLP arsenic for sulphide-rich mine tailing remediation in Ghana,West Africa     

Gordon Foli  Simon K. Y. Gawu 《Environmental Earth Sciences》2018,77(8):309

Toxicity characteristic leaching procedure (TCLP) is a versatile short-term leaching protocol used to estimate the release of toxic metals from waste prior to disposal to a repository. This paper uses the integrated TCLP leachate data from tailings, tailings dam monitoring borehole data, and acidity ratio (AR) range of sulphide-rich ores to simulate the environmental TCLP As in tailings at the AngloGold Ashanti Obuasi mine in Ghana. The aim was to incorporate long-term leaching characteristics of tailings to minimise the risk of TCLP As test failure. The mean As concentration and pH value are 2.26 mg/l and 5.7 in TCLP leachate, 0.35 mg/l and 6.7 in monitoring boreholes, and?<?0.01 mg/l and 5.7 in control boreholes, respectively. The evaluation of the TCLP As data using a one-sample t test performed at 80% confidence interval has the upper confidence limit (UCL) of 2.41 mg/l; this value which constitutes the short-term characterised environmental TCLP As is below the USEPA criterion of 5 mg/l and, therefore, qualifies the waste as safe for disposal. Alternatively, TCLP leachate, borehole and AR data were integrated to simulate the long-term environmental TCLP As of 2.40 mg/l and pH value of 5.7, and As concentration and pH value of 0.01 mg/l and 6.7 in monitoring boreholes, respectively. Such laboratory simulations of TCLP As leaching aimed at achieving 0.01 mg/l in field monitoring data would provide a more robust predictive value for environmental management decision making due to long-term considerations.  相似文献   

Robust response to hydro-climatic change in electricity generation planning     

Simon C. Parkinson  Ned Djilali 《Climatic change》2015,130(4):475-489

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Loose programming of GIS workflows with geo‐analytical concepts     

Johannes F. Kruiger  Vedran Kasalica  Rogier Meerlo  Anna‐Lena Lamprecht  Enkhbold Nyamsuren  Simon Scheider 《Transactions in GIS》2021,25(1):424-449

Loose programming enables analysts to program with concepts instead of procedural code. Data transformations are left underspecified, leaving out procedural details and exploiting knowledge about the applicability of functions to data types. To synthesize workflows of high quality for a geo‐analytical task, the semantic type system needs to reflect knowledge of geographic information systems (GIS) at a level that is deep enough to capture geo‐analytical concepts and intentions, yet shallow enough to generalize over GIS implementations. Recently, core concepts of spatial information and related geo‐analytical concepts were proposed as a way to add the required abstraction level to current geodata models. The core concept data types (CCD) ontology is a semantic type system that can be used to constrain GIS functions for workflow synthesis. However, to date, it is unknown what gain in precision and workflow quality can be expected. In this article we synthesize workflows by annotating GIS tools with these types, specifying a range of common analytical tasks taken from an urban livability scenario. We measure the quality of automatically synthesized workflows against a benchmark generated from common data types. Results show that CCD concepts significantly improve the precision of workflow synthesis.  相似文献   

Cryptotephras in the Lateglacial ICDP Dead Sea sediment record and their implications for chronology     

Ina Neugebauer  Daniela Müller  Markus J. Schwab  Simon Blockley  Christine S. Lane  Sabine Wulf  Oona Appelt  Achim Brauer 《Boreas: An International Journal of Quaternary Research》2021,50(3):844-861

Due to a lack of visible tephras in the Dead Sea record, this unique palaeoenvironmental archive is largely unconnected to the well-established Mediterranean tephrostratigraphy. Here we present first results of the ongoing search for cryptotephras in the International Continental Drilling Program (ICDP) sediment core from the deep Dead Sea basin. This study focusses on the Lateglacial (~15–11.4 cal. ka BP), when Lake Lisan – the precursor of the Dead Sea – shrank from its glacial highstand to the Holocene low levels. We developed a glass shard separation protocol and counting procedure that is adapted to the extreme salinity and sediment recycling of the Dead Sea. Cryptotephra is abundant in the Dead Sea record (up to ~100 shards cm^-3), but often glasses are physically and/or chemically altered. Six glass samples from five tephra horizons reveal a heterogeneous geochemical composition, with mainly rhyolitic and some trachytic glasses potentially sourced from Italian, Aegean and Anatolian volcanoes. Most shards likely originate from the eastern Anatolian volcanic province and can be correlated using major element analyses with tephra deposits from swarm eruptions of the Süphan Volcano ~13 ka BP and with ashes from Nemrut Volcano, presumably the Lake Van V-16 volcanic layer at ~13.8 ka BP. In addition to glasses that match the TM-10-1 from Lago Grande di Monticchio (15 820±790 cal. a BP) tentatively correlated with the St. Angelo Tuff of Ischia, we further identified a cryptotephra with glass analyses which are chemically identical with those of the PhT1 tephra in the Philippon peat record (13.9–10.5 ka BP), and also a compositional match for the glass analyses of the Santorini Cape Riva Tephra (Y-2 marine tephra, 22 024±642 cal. a BP). These first results demonstrate the great potential of cryptotephrochronology in the Dead Sea record for improving its chronology and connecting the Levantine region to the Mediterranean tephra framework.  相似文献   

Analytical and numerical modelling of air trapping during wetting of unsaturated soils     

Scarfone  Riccardo  Wheeler  Simon J. 《Acta Geotechnica》2022,17(8):3499-3513

Acta Geotechnica - At high values of degree of saturation, the apparent soil water retention curve (SWRC) measured in a wetting test in the laboratory may differ from the true SWRC, because of the...  相似文献   

The Laacher See Tephra discovered in southernmost Sweden          下载免费PDF全文

Simon A. Larsson  Stefan Wastegård 《第四纪科学杂志》2018,33(5):477-481

We present the first geochemically confirmed finding of the Laacher See Tephra (LST) on the Swedish mainland, now the northernmost extension of the LST. Sediments were sampled at the Körslättamossen fen, southernmost Sweden, and a high‐concentration cryptotephra occurrence (>65 000 shards cm^?3) of the LST was found in a sequence of calcareous gyttja. Tephra identification was confirmed by geochemical analysis using field‐emission electron probe microanalysis and through comparison of the results with published LST data from proximal sites and distal sites north‐east of Laacher See. The LST has previously been divided into eruption phases suggested to have spread in several dispersal fans, but it was not possible to confidently determine the phase of the tephra here closer than to the MLST or ULST. The finding of the LST presented here further strengthens the potential of tephrochronological studies in the south Scandinavian region.

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Melt inclusion evidence for CO2-rich melts beneath the western branch of the East African Rift: implications for long-term storage of volatiles in the deep lithospheric mantle     

T. R. Hudgins  S. B. Mukasa  A. C. Simon  G. Moore  E. Barifaijo 《Contributions to Mineralogy and Petrology》2015,169(5):1-18

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