On asymmetries of solar spectral lines

The profiles of 43 lines have been observed at the centre and near the limb of the solar disk. Their asymmetry decreases towards the limb, and increases with the equivalent width and the mean heigth of line formation; no relation was found between the asymmetry and the line excitation potential, nor with the degree of ionization, nor with the usually adopted macroturbulent velocity. The asymmetry appears to be due to radial movements.     

Linking hydrological, infinite slope stability and land-use change models through GIS for assessing the impact of deforestation on slope stability in high Andean watersheds

In the Ecuadorian Andes, episodic slope movements comprising shallow rotational and translational slides and rapid flows of debris and soil material are common. Consequently, not only considerable financial costs are experienced, but also major ecological and environmental problems arise in a larger geographical area. Sediment production by slope movement on hillslopes directly affects sediment transport and deposition in downstream rivers and dams and morphological changes in the stream channels. In developing countries world-wide, slope movement hazards are growing: increasing population pressure and economic development force more people to move to potentially hazardous areas, which are less suitable for agriculture and rangelands.This paper describes the methods used to determine the controlling factors of slope failure and to build upon the results of the statistical analysis a process-based slope stability model, which includes a dynamic soil wetness index using a simple subsurface flow model. The model provides a time-varying estimate of slope movement susceptibility, by linking land-use data with spatially varying hydrologic (soil conductivity, evapotranspiration, soil wetness) and soil strength properties. The slope stability model was applied to a high Andean watershed (Gordeleg Catchment, 250 ha, southern Ecuadorian Andes) and was validated by calculating the association coefficients between the slope movement susceptibility map of 2000 and the spatial pattern of active slope movements, as measured in the field with GPS. The proposed methodology allows assessment of the effects of past and future land-use change on slope stability. A realistic deforestation scenario was presented: past land-use change includes a gradual fragmentation and clear cut of the secondary forests, as observed over the last four decades (1963–2000), future land-use change is simulated based on a binary logistic deforestation model, whereby it was assumed that future land-use change would continue at the same rate and style as over the last 37 years (1963–2000).     

Uranium and Multi-element Release from Orthogneiss and Granite (Austria): Experimental Approach Versus Groundwater Composition

In this study, the release of elements and in particular U from five Austrian orthogneiss and granite samples into a CO₂-bearing solution was investigated to describe the initial phase (24 h) of leaching focusing on the impact of ferrous (hydro)oxide formation. Experiments were conducted at ambient temperature by flushing CO₂:N₂ gas through the reactive solution (pH_initial?~?4.3) at a liquid:solid ratio of 10:1 with and without a reducing agent. The chemical evolution of the leaching solution was dominated by incongruent dissolution of silicates showing a parabolic kinetic behavior due to protective surface formation most likely caused by precipitation of amorphous Fe^III/Al hydroxides. However, the relative distribution of Ca, Mg and Sr in the leaching solution excellently traced the individual bulk rock composition. The mobilization of U was highly prevented under oxidizing conditions by sorption onto ferrous (hydro)oxides, which were precipitating through ongoing silicate leaching. Therefore, the leaching behavior of individual U-bearing minerals was less relevant for U release. At reducing conditions, the above elements were accumulated in the solution, although an oversaturation regarding U^IVO₂ was calculated. This indicates its inhibited formation within the experimental run time. The composition of experimental leaching solutions did not reflect analyzed groundwater compositions from investigated local rock-type aquifers indicating that reaction rate constants of siliceous rocks significantly differ between values found in nature and in the laboratory. Change in active mineral surface areas with ongoing weathering, accumulation of secondary precipitates, leached layer formation and given reaction time are key factors for distinct elemental release.     

Fazies-Analyse im Paläozoikum des Oslo-Gebietes

All available bathymetric criteria (lithology, sedimentary structures, fossil orientation, current features benthos, and trace fossils) are used to reconstruct the sedimentary history and the crustal movements of the Oslo district during Cambrian, Ordovician, and Silurian times. Two phases of basin development and crustal subsidence are recognized, separated by an episode of crustal rest or uplift that resulted in the deposition of shallow marine and conglomeratic sediments at the close of Ordovician times.     

Geochemical evolution of groundwater in the Maneadero coastal aquifer during a dry year in Baja California, Mexico

Water pumped from 25 shallow wells (<31 m) in the Maneadero unconfined coastal aquifer was studied geochemically in order to determine the short-term compositional variability of the aquifer due to seawater intrusion during a drier than normal year (Fall 2001 to Fall 2002). The groundwater was commonly found to be mixed with seawater, with TDS concentrations in November 2002 ranging from 0.99 to 9.46 g l^–1, having an intermediate Na⁺Cl^– to Ca²⁺Cl^– water-type. Rapid recharge events of short duration, after low and short rainfall events during the study period, are suggested from short-term fluctuations in water quality. Seawater intrusion is progressing faster in the central and southern coastal sections of the aquifer and has recently affected the quality of the sites pumping water to the nearby city of Ensenada. Only one of the wells used for the Ensenada water supply had a TDS concentration lower than the 1.0 g l^–1 official limit. Low flow rates and high residence times of water are inferred to be the cause for high alkalinity in the east-central section of the aquifer. High NO₃ in the east-central aquifer indicates that any NO₃ infiltration due to fertilizer use was only slightly dispersed. After a short rainfall season during winter 2001, a significant decrease was seen for the previously most enriched site. However, concentrations above the 10 mg l^–1 official limit persisted in 2002, affecting one well for urban supply (15.9 mg l^–1). The water from this well is nevertheless mixed with better-quality water from other wells before being distributed through the citys piping system.

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Resumen Se estudió la geoquímica de aguas bombeadas por medio de 25 pozos no muy profundos (<31 m) en el acuifero costero no confinado de Maneadero con el objetivo de determinar la variación de la composición en el corto plazo en el acuifero por la intrusión de agua de mar durante un año más seco de lo normal (otoño 2001 a otoño 2002). Se observó que comúnmente las aguas subterráneas estaban mezcladas con agua de mar, con concentraciones de sólidos totales disveltos (STD) de entre 0.99--9.46 g l^–1 y un tipo de agua intermedia Na⁺Cl^– to Ca²⁺Cl^–. A partir de las fluctuaciones en la calidad del agua en el corto plazo se puede inferir que se dan eventos de recarga rápida de poca duración después de eventos de poca lluvia de poca duración y poco volumen durante el periodo de estudio. La intrusión de agua de mar está progresando más rápido en el centro y sur del acuifero costero y ha afectado recientemente la calidad de los sitios de bombeo de agua para la ciudad de Ensenada. Solamente uno de los pozos usados para el abastamiento de Ensenada tiene un STD por debajo del límite oficial de 1.0 g l^–1. Se presume que las razones lentas de flujo y los tiempos de residencia largos del agua son la causa de la alta alcalinidad en el centro-este del acuifero. Una concentración alta de NO₃ en el este-centro del acuifero indica que cualquier infiltración de NO₃ por aplicación de fertilizantes ha sido poco dispersad. Después de poca lluvia en el invierno de 2001, se observó una disminución importante en la zona previamente más enriquecida. Sin embargo, concentraciones sobre el límite oficial de 10 mg l^–1 continuaron en 2002, afectando a un pozo para suministro de agua urbana (15.9 mg l^–1). El agua extraída de este pozo es mezclada con agua de mejor calidad y se distribuye por el sistema urbano de suministro de agua.

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Résumé Leau de pompage de 25 puits peu profonds (<31 m) situés dans laquifère côtier non-confiné de Maneadero a été étudiée dans le but de déterminer la variation géochimique à court terme qui résulte de lintrusion deau de mer lors dune année plus sèche quà lhabitude (automne 2001 à automne 2002). Leau souterraine est souvent retrouvée mélangée avec de leau de mer, avec des concentrations en résidus solides dissous (RSD) qui sétalent entre 0.99 et 9.46 g l^–1 pour novembre 2002, avec un type intermédiaire en Na⁺Cl^– jusquà Ca²⁺Cl^–. Les processus suggérés pour les fluctuations rapides de la qualité de leau sont des événements de recharge de courte duré suite à de faibles et brèves périodes de précipitations. Lintrusion deau de mer progresse plus rapidement dans les parties centrales et sud de laquifère côtier où la qualité de leau pompée vers la ville de Ensenada a récemment été affectée. Un seul des puits utilisés par la ville de Ensenada pour lapprovisionnement en eau potable a une concentration en RSD sous la limite officielle permise de 1.0 g l^–1. Le temps de résidence élevé et le faible taux découlement de leau souterraine sont présumés être la cause de lalcalinité élevée dans la partie centrale-est de laquifère. La concentration élevée en NO₃ dans cette partie de laquifère indique que la totalité de linfiltration de NO₃ dû à lutilisation de fertilisants ne sest que très peu dispersée. Suite à une courte saison des pluies à lhiver 2001, une diminution substantielle a été notée au site qui était le plus enrichi avant la saison des pluies. Malgré tout, des concentrations dépassant la limite officielle permise de 10 mg l^–1 ont persisté, affectant un puits utilisé pour lapprovisionnement urbain (15.9 mg l^–1). Leau provenant de ce puits est toutefois mélangée avec de leau de meilleure qualité provenant dautres puits avant dêtre distribuée par laqueduc municipal.

     

Groundwater optimization model for sustainable management of the Valley of Puebla aquifer, Mexico

The Valley of Puebla aquifer (VPA), at the central region of Mexico, is subject to intensive exploitation to satisfy the urban and industrial demand in the region. As a result of this increased exploitation, a number of state and federal agencies in charge of water management are concerned about the problems associated with the aquifer (decline of groundwater table, deterioration in water quality, poor well productivity and increased pumping and water treatment costs). This study presents a groundwater management model that combines “MODFLOW” simulation with optimization tools “MODRSP”. This simulation–optimization model for groundwater evaluates a complex range of management options to identify the strategies that best fit the objectives for allocating resources in the VPA. Four hypothetical scenarios were defined to analyze the response of the hydrogeological system for future pumping schemes. Based on the simulation of flow with the MODFLOW program, promising results for the implementation of the optimization of water quantity were found in scenarios 3 and 4. However, upon comparison and analysis of the feasibility of recovery of the piezometric level (considering the policy of gradual reductions of pumping), scenario 4 was selected for optimization purposes. The response functions of scenario 4 were then obtained and optimized, establishing an extraction rate of 204.92 millions of m³/year (Mm³/year). The reduction in groundwater extraction will be possible by substituting the volume removed by 35 wells (that should be discontinued) by the same volume of water from another source.     

Can Jupiters be found by monitoring Galactic bulge microlensing events from northern sites?

In 1998 the EXPORT team monitored microlensing event light curves using a charge-coupled device (CCD) camera on the IAC 0.8-m telescope on Tenerife to evaluate the prospect of using northern telescopes to find microlens anomalies that reveal planets orbiting the lens stars. The high airmass and more limited time available for observations of Galactic bulge sources make a northern site less favourable for microlensing planet searches. However, there are potentially a large number of northern 1-m class telescopes that could devote a few hours per night to monitor ongoing microlensing events. Our IAC observations indicate that accuracies sufficient to detect planets can be achieved despite the higher airmass.     

Polarimetry of main belt asteroids: Wavelength dependence

New UBVRI polarimetric observations of ten asteroids, including space mission targets 1 Ceres and 21 Lutetia, are presented. These observations were obtained with the 1.25-m telescope of the Crimean Astrophysical Observatory and have been used to study the wavelength dependence of polarization for a sample of asteroids belonging to the M and low albedo classes. A more general analysis including also a larger data set of UBVRI polarimetric observations available in the literature for more than 50 main belt asteroids belonging to different taxonomic classes shows that the variation of the polarization degree Pr as a function of wavelength is generally well described by a linear trend. It typically does not exceed 0.2% in the studied spectral range 0.37-0.83 microns and tends to increase for increasing phase angle. Asteroids belonging to the S and M classes are found to exhibit a deeper negative branch and smaller positive polarization for increasing wavelength (negative sign of the slope of ΔPr/Δλ). Since the objects belonging to these classes are known to exhibit reddish reflectance spectra, the observed wavelength behavior of negative polarization contradicts the well-known inverse correlation of Pmin and albedo. Low albedo asteroids show larger dispersion of spectral slopes, but the overall trend is characterized by a shallower negative branch and a larger positive polarization for increasing wavelength (positive sign of the slope of ΔPr/Δλ). A few exceptions from this general trend are discussed. The observed variety in the wavelength dependence of asteroid polarization seems to be mainly attributed to surface composition.