WSO-UV—ultraviolet mission for the next decade

The World Space Observatory UltraViolet (WSO–UV) is an international space mission devoted to UV spectroscopy and imaging. The observatory includes a 170 cm aperture telescope capable of high-resolution and long slit low-resolution spectroscopy, and deep UV and optical imaging. The observatory is designed for observations in the ultraviolet domain where most of astrophysical processes can be efficiently studied with unprecedented capability.     

Fast numerical method for growth and retreat of subsurface ice on Mars

Subsurface water ice on Mars evolves due to exchange of vapor with the atmosphere, in the form of loss of ice to the atmosphere or in the form of the growth of interstitial ice. Described here is an accelerated numerical method for the long-term evolution of subsurface ice. This accelerated method is five orders of magnitude faster than explicit vapor transport calculations, enabling fundamentally new types of climate models. Its speed matches that of purely thermal models. The speedup is achieved primarily by solving time-averaged equations for vapor transport and ice volume change. Processes incorporated are growth of interstitial pore ice, retreat of pore ice, retreat of an ice sheet, and retreat of pore ice due to geothermal heating from below. Two example applications illustrate this numerical method’s capabilities. Near the permafrost margin at 55° latitude, ice is periodically depleted and slowly recharged, leading to a pore ice layer estimated to be currently no more than a few meters thick. At the Phoenix Landing Site, it shows the formation of a three layered structure, whereby the layer of pore ice can be very thin.     

Discriminant analysis for estimation of groundwater age from hydrochemistry and well construction: application to New Zealand aquifers

Concentrations of tritium, chlorofluorocarbons and sulfur hexafluoride have been measured at over 100 groundwater monitoring sites across New Zealand, followed by interpretation of groundwater age distribution using the exponential-piston flow model. Interpreted mean residence times ranged from less than 1 year to more than 100 years, with the 25th, 50th (median) and 75th percentiles being approximately 10, 40 and 100 years, respectively. Classification functions derived from discriminant analysis and based on nine input variables (well depth, electrical conductivity and the concentrations of the ions Na, K, Ca, Mg, HCO₃, Cl and SO₄) allowed assignment of 71% of the sites to the correct of four age categories (mean residence time 10 years or less, 11–40 years, 41–100 years, or more than 100 years). The discriminant analysis classification functions were more effective than regression methods for estimating groundwater age from hydrochemistry and well depth, and can thus be used to predict the groundwater age category for any monitoring site in New Zealand.     

Microborer ichnocoenoses in Quaternary corals from New Caledonia: reconstructions of paleo-water depths and reef growth strategies in relation to environmental changes

Coral reef growth and development depend on several environmental factors, including tectonic and climatic parameters and local ecological drivers. Reef growth is especially sensitive to sea-level variations. Paleo-water depth reconstructions are essential tools used to determine reef growth patterns during different periods of reef growth. Assemblages of corals and/or coralline algae have been commonly used in such paleodepth reconstructions. This study shows that using microendolith ichnocoenoses can sometimes provide better accuracy than traditional coralgal analyses, particularly in the depth-range 0–10 m where coralgal assemblages usually show broad distribution ranges. Holocene and Pleistocene cores from two barrier reef sites on the west coast of Grande Terre in New Caledonia are examined here. Holocene reef development at these sites feature examples of microendolith ichnocoenoses that document rapid environmental changes and small sea-level variations of about 2–5 m in amplitude, and record these changes with more accuracy than coral and coralline algae assemblages which are highly dependant on the hydrodynamic energy of the setting. During the Pleistocene, which was less chronologically constrained, the microendolith ichnocoenoses also reflect paleo-water depths and reef-growth patterns at different periods of reef history.     

Longitudinal velocities in a clay during plastic compression

Summary During uniaxial compression of clay cylinders it was observed that the longitudinal velocity decreased as each load increment was applied and then increased under constant stress. It is suggested that the load increment induces an increase in pore water pressure thereby reducing the effective stress. The velocity is dependent upon the effective stress and it decreases accordingly. The velocity then increases due to the dissipation of the pore pressure.     

Métamorphisme hydrothermal en faciès salins et pénésalins sur l'exemple du complexe salifère de l'extrême Nord Tunisien

Résumé Les roches sédimentaires des formations salifères de l'extrême Nord tunisien ont fréquemment subies une recristallisation ou une dolomitisation notable, à laquelle se superpose souvent un envahissement de minéraux automorphes, quartz et feldspaths principalement. L'étude des inclusions fluides de ces cristaux conduit à des conditions thermométriques de genèse qui dépassent le stade d'une simple diagenèse. Les transformations subies relèvent davantage d'un épimétamorphisme, en milieu aquifère hypersalin, lié à des anomalies thermiques vraisemblablement en rapport avec des manifestations volcaniques.

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Hydrothermal low grade metamorphism within saline and penesaline facies with reference to the saliferous complex in Northern Tunisia

The sedimentary rocks of saliferous formations in the tunisian far North have gone through frequent recrystallization or a notable dolomitization which an invading of idiomorph minerals mainly made up of quartz and feldspar crystals is frequently added to. Studies carried out on fluid inclusions from these crystals lead thermometric figures clearly exceeding the range of values met with in diagenesis. New paragenesis are best related to low grade metamorphism in aquiferous hypersalted medium bearing relation with thermal anomalies likely connected to volcanism.

     

Zur Entstehung der Trou-Au-Natron-Caldera (Tibesti-Gebirge,Zentral-Sahara) aus photogeologischer Sicht

Aerial photographs of the “Trou au Natron” and “Doôn Kinimi” calderas (Tibesti Mts., Central Sahara) have been interpreted and plotted in order to obtain qualitative and quantitative information. The Trou au Natron sets an example for the possibility to identify the origin of a caldera by means of analysing aerial photographs only. Special attention is paid to the pyroclastics, because they had been used so far as an argument for the explosive origin of the Trou au Natron. It is possible to point out that no immediate relation exists between pyroclastics and the formation of the caldera and that the Trou au Natron — contrary to former opinions — presents a collapse caldera.     

Characterization of sediments in an abandoned mining area; a case study of Mansfeld region,Germany

The distribution of selected heavy metals, including some radionuclides, metalloids and non-metals was determined in stream sediments in a region influenced by abandoned copper mining and ore processing activities. A considerable amount of the ore processing waste with a very complex composition and highly elevated concentrations of zinc, sulfur, lead, copper, arsenic, and a lot of other elements in the range between 100 and 1,000 mg/kg (Sb, Mn, Ni, Cr, Cd, Hg, and Ag) was piled up on mine dumps. The dispersion of the pollutants originating from this source and their environmental impact were investigated. Both, sediments and original waste material were studied to indicate the pathways and the mobilization behavior of different pollutants. For this purpose, the process of the elution of pollutants by application of different fractionation schemes was studied. The capabilities of different analytical techniques are shown for the analysis of solid samples (X-ray fluorescence spectrometry, Gamma-spectrometry) and liquid ones (ICP-atomic emission spectrometry, ICP-mass spectrometry and different techniques of atomic absorption). Additionally, the coupling of ion chromatography and ICP-MS detection was used to study the distribution of arsenic species in the sediment cores of a lake which acts as a natural sink for the region.     

Longitudinal velocity patterns and bed morphology interaction in a rill

Present‐day understanding of rill dynamics is hampered by a lack of detailed data on velocity distributions in rills. The latter are dif?cult to collect with traditional techniques due to the very low water depths and the relatively high ?ow velocities in rills. The objectives of this paper were to investigate the feasibility of miniaturized acoustic Doppler velocimeter (mADV) measurements in rill ?ow and to explore longitudinal variations in ?ow velocities and their relationship with rill bed morphology. Detailed data on longitudinal ?ow velocity were required to achieve these objectives. A 1·8 m long rill was formed freely in a ?ume at 5° slope and 0·001 m³ s^?1 discharge. Rill topography was characterized by an alternation of steps and pools. The ?ume surface was then ?xed to preserve rill roughness. A topographical scanning of the entire ?ume surface was made. Velocity was measured with a mADV along the rill, and at different depths. Flow depth in a longitudinal direction was also measured using an elevation gauge. A strong relationship exists between rill topography and ?ow hydraulics. Over steps, ?ow was unidirectional and rapidly accelerating until a threshold Froude number (Fn) value between 1·3 and 1·7 was reached and a hydraulic jump occurred leading to the formation of a pool. In the pool, the ?ow pattern was multidirectional and complex. The ?ow was subcritical when leaving the pool and accelerated over the next step until the threshold Froude number value was again reached. Energy loss in the rill was concentrated in the pools, mainly due to the action of a hydraulic jump. This mechanism of energy dissipation appeared to be an essential factor in rill formation and bedform evolution. Copyright © 2004 John Wiley & Sons, Ltd.     

Soil detachment and transport on field‐ and laboratory‐scale interrill areas: erosion processes and the size‐selectivity of eroded sediment

Field‐ and laboratory‐scale rainfall simulation experiments were carried out in an investigation of the temporal variability of erosion processes on interrill areas, and the effects of such variation upon sediment size characteristics. Poorly aggregated sandy soils from the semi‐arid environment of Senegal, West Africa, were used on both a 40 m² field plot and a 0·25 m² laboratory plot; rainfall intensity for all experiments was 70 mm h^?1 with a duration of 1 to 2 hours. Time‐series measurements were made of the quantity and the size distribution of eroded material: these permitted an estimate of the changing temporal balance between the main erosion processes (splash and wash). Results from both spatial scales showed a similar temporal pattern of runoff generation and sediment concentration. For both spatial scales, the dominant erosional process was detachment by raindrops; this resulted in a dynamic evolution of the soil surface under raindrop impact, with the rapid formation of a sieving crust followed by an erosion crust. However, a clear difference was observed between the two scales regarding the size of particles detached by both splash and wash. While all measured values were lower than the mean weight diameter (MWD) value of the original soil (mean 0·32 mm), demonstrating the size‐selective nature of wash and splash processes, the MWD values of washed and splashed particles at the field scale ranged from 0·08 to 0·16 mm and from 0·12 to 0·30 mm respectively, whereas the MWD values of washed and splashed particles at the laboratory scale ranged from 0·13 to 0·29 mm and from 0·21 to 0·32 mm respectively. Thus only at the field scale were the soil particles detached by splash notably coarser than those transported by wash. This suggests a transport‐limited erosion process at the field scale. Differences were also observed between the dynamics of the soil loss by wash at the two scales, since results showed wider scatter in the field compared to the laboratory experiments. This scatter is probably related to the change in soil surface characteristics due to the size‐selectivity of the erosion processes at this spatial scale. Copyright © 2006 John Wiley & Sons, Ltd.