Hydrochemical dynamics of TOC and NO3 − contents as natural tracers of infiltration in karst aquifers

Analysis of Total Organic Carbon (TOC) and NO₃ ^? contents in the water at six springs in the province of Malaga (Southern Spain), sampled under different hydrologic conditions, revealed two different hydrochemical behaviour patterns for these natural tracers of infiltration. TOC content increased during every recharge period, following the rapid arrival of water infiltrating through the soil. On the other hand, NO₃ ^? content only rose during the first flood episodes (normally in autumn), and fell during the winter and spring ones. This difference is consequence of the distinctive biogeochemical kinetics of nitrogen with respect to organic carbon, both in the soil and within the aquifer. Unlike the mineralisation undergone by TOC from the surface to the spring, the NO₃ ^? ion remains in the aquifer almost unaffected, due to the oxidizing conditions prevailing within the karst medium, which do not allow its denitrification and favour its preservation within the saturated zone. In non-polluted aquifers, TOC and NO₃ ^? have a common origin in the soil and can be used to determine infiltration processes and the hydrogeological functioning of karst aquifers. Their different hydrochemical evolution provides information about mineralization and degradation processes of organic matter within karst aquifers, which can be used to validate the vulnerability to contamination in this type of medium.     

Interannual variability of air temperature inversions in ice-free area of northern James Ross Island,Antarctica

Theoretical and Applied Climatology - Air temperature inversions are common features in Antarctica, especially in the interior where they are observed nearly year-round. Large temporal variability...     

Analysis and interpretation of the seismic response of RC buildings in Concepción during the February 27, 2010, Chile earthquake

Observed trends in the seismic performance of eight severely damaged reinforced concrete (RC) structures after the February 27, 2010, Chile earthquake are presented in this article. After a reconnaissance and surveying process conducted immediately after the earthquake, several aspects not conventionally considered in building design were observed in the field. Most of the considered structures showed extensive localized damage in walls of lower stories and first basements. Several factors indicate that damage was brittle, and occurred mainly in recent RC structures supported on soft soils with some degree of vertical and/or horizontal irregularity. Non-ductile behavior has been inferred due to the lack of evidence of spread damage in the structure, and the fact that very similar structural configurations existed nearby without apparent damage. Some key aspects in understanding the observed damage are: geographical orientation of the building, presence of vertical and horizontal irregularities, wall thickness and reinforcement detailing, and lack of sources for energy dissipation. Additionally, results of a building-code type analysis are presented for the 4 most critical buildings, and Demand/Capacity ratios are calculated and compared with the observed behavior. It is concluded that the design codes must be revised relative to wall design provisions.     

Determination of actual limit angles to the surface and their comparison with the empirical values in the Upper Silesian Basin (Czech Republic)

This study deals with the determination of the actual limit angles in the long-term formed subsidence basin in the Czech part of the Upper Silesian Basin (the remaining part lays in Poland). Here there was the most extensive underground exploitation of black coal in the north-east of the Czech Republic. A limit angle is absolutely decisive in the determination of deep mining influences in relation to the current and future utilisation of this territory. The two CSM and Paskov mine localities on the edge of the subsidence basin were selected for this study, since they could not have been affected by mining in neighbouring mines. On the grounds of the long-term levelling monitoring of points on the surface which started prior to mining, the horizontal distance between the mined out area and the undisturbed ground surface was identified. The impact of limit angle on the surface was calculated by means of the horizontal distance and the established mining depth. Such identified actual limit angles reached the values of 36° at the CSM Mine and 25° for the Paskov Mine. The calculated values are significantly lower when compared with the currently applied empirical values of 57° for the CSM Mine and 56° for the Paskov Mine. This means that the extent of the undermining effects is unambiguously wider by 611 m at the CSM Mine and by 883 m at the Paskov Mine. This study thus establishes the existence of a significantly vaster area influenced by coal deep mining than previously expected. The identified facts lead to the conclusion that regular revisions and follow-up updates of the empirically determined parameters are recommended.     

Support vector machines and gradient boosting for graphical estimation of a slate deposit

Critical for an efficient and effective exploitation of a slate mine is to obtain information on its technical quality, in other words, on the exploitability potential of the deposit. We applied support vector machines (SVM) and LS-Boosting to the assessment of the technical quality of a new unexploited area of a mine, and compared the results to those obtained for kriging and neural networks. Firstly we analyzed the relationship between kriging and semi-parametric SVM in a regularization framework and explored the different alternatives for training these networks. Subsequently, in an attempt to combine both radial and projection structures, we formulated a boosting technique for radial basis function (RBF) networks defined over projections in the input space (RBFPP). The application of these techniques to our test drilling data demonstrated a similar level of performance for all the estimators examined, with the main difference occurring in the shape of the respective deposit reconstructions. Therefore, in choosing between the different techniques, an essential aspect will be their ability to reproduce the morphological characteristics of the true process. In this paper we also evaluate the benefits of using the estimated covariogram as the kernel of the SVMs and compare the sparsity of the different solutions. The results obtained show that the selection of a standard kernel that ignores the variability structure of the problem produces poorer results than when the estimated covariogram is used as the kernel.The research of J. Taboada was supported by the European Union, FEDER program, Project 1FD97–0091. The research of W. González-Manteiga was supported by Ministerio de Ciencia y Tecnología of the Spanish Government, Project BFM2002–03213. The authors wish to thank the associate editor and an anonymous referee for stimulating comments.     

Upwelling-triggered near-geostrophic recirculation in an equatorward facing embayment

Underway current velocity profiles were combined with hydrographic profiles at the entrance to Tongoy Bay, an equatorward facing bay in north-central Chile, with the objective of determining its exchange hydrodynamics. To the west, Tongoy Bay is bounded by Lengua de Vaca Point, a ～6 km-long northward protruding peninsula. Observations were obtained during three surveys (April 2005, December 2005, May 2009) along cross-bay transects for at least one full day. During the surveys, winds were upwelling-favorable and displayed diurnal variations. Non-tidal (tidally averaged) flows showed a consistent clockwise or southern hemisphere cyclonic, recirculation during the three surveys. This recirculation was likely part of a cyclonic gyre (10–20 km in diameter), not entirely resolved by the surveys, and formed by flow separation off Lengua de Vaca Point. Estimates of the baroclinic pressure gradient, combined with analytical solutions of density-driven and wind-driven flows, indicated that the recirculation in Tongoy Bay was nearly in geostrophic balance. An ageostrophic contribution to the dynamics was related to frictional effects derived from local upwelling-favorable winds. A linear superposition of the analytically derived density-driven and wind-driven exchange resulted in a flow pattern that resembled the observed net exchange flows at the bay mouth.     

Cyclical salt efflorescence weathering: an invisible threat to the recovery of underground mine environment for tourist exploitation

Enhancing the value of an underground mine environment for tourist exploitation involves altering the physico-chemical balance of stone materials whose original mechanical properties guaranteed the structural stability of the site’s galleries and chambers. Humidity and temperature changes caused by the public exhibition of this kind of assets are the main causes of such disorders. After the intervention in the Agrupa-Vicenta mine in La Union (Spain) there were still runoff-water leaks into the mine. These water runoffs through the fault and schistosity planes of the enclosing rock mass give rise to salt precipitation over time. Adapting this mine and turning it into a museum have meant a decrease in relative indoors humidity and an increase in temperature. These variations have caused rocks, which were stable in the original conditions, to increase their rate of physico-chemical weathering due to the polycyclic supergene alteration of the metal sulfides they contain. The resulting release of sulfates into the solution and their subsequent precipitation as single and double salt efflorescence causes haloclasty, deteriorating the rock’s mechanical properties and diminishing the structural stability of the operation. This paper presents the results of characterizing the supergene mineral phases of salt efflorescence in the rock bed enclosing an underground sulfide mine value enhanced for tourist exploitation. Dangers for the structural stability of this type of architectural intervention, associated to the formation of efflorescences, are also identified; these efflorescences are caused by the weathering of rocks that make up its supporting structure.     

Tectonic modification of the Australian North-West Shelf: episodic rejuvenation of long-lived basin divisions

Neogene collision between Australia and the Banda Arc modified two adjacent depocentres within Australia's North‐West Shelf, the Browse and Bonaparte Basins. We identify two components of this modification: (1) continuous long‐wavelength amplification of Permo‐Carboniferous basement topography, and (2) flexure and normal faulting of Triassic–Recent sedimentary cover. Although this deformation was continuous across the Browse and Bonaparte Basins, the degree of basement architectural control, mechanisms of fault linkage and distribution of syntectonic accommodation space varied significantly between the two basins. These variations reflect fundamental differences in the structural relief, amplitude and depth of rifted basement on either side of a rupture‐barrier‐style accommodation zone, the Browse/Bonaparte Transition. This long‐lived architectural divide, of which there is no discrete structural expression, was amplified by Neogene collision. We examine tectonic rejuvenation of the Browse/Bonaparte Transition and describe a mechanism for actively sustaining long‐lived segmentation of the continental shelf.     

An effective visualization and comparison of online terrain draped with multi-sensor satellite images

The objective of this paper is to discuss the effectiveness of visualizing online 3D terrain draped with different satellite imageries. The topographic data of the study area were obtained from the contour maps of Universiti Putra Malaysia, Selangor, Malaysia. The high resolution satellite imageries used in this project involving QUICKBIRD (0.6 m resolution), IKONOS (1 m resolution), and SPOT5 (5 m resolution). R2V software was used for editing the contour data, whereas Arc GIS was used for overlaying the imageries over the 3D terrain data. Then the data were exported into Virtual Reality Markup Language to compare the effectiveness of different satellite imageries based on the data file size, imageries size, number of images tile, loading time during office hours (from 8 a.m. to 5 p.m.) and out of office hours (after 5 p.m.), frame rate per second, and visualization quality. The results revealed that IKONOS satellite imageries are better for an effective online 3D terrain visualization utilizing GIS data even though it has lower resolution compared to QUICKBIRD.