Seismic spectra on soil with uncertain properties

Expected spectral ordinates and their standard deviations are computed for ground motions produced by SH waves at the surface of a homogeneous soil formation resting on a half-space of rock. Wave transmission is idealized as linear and one-dimensional. Uncertainties about soil properties are taken into account using various approximations: a Taylor series expansion of the Fourier spectrum magnification factors with different numbers of terms and different intervals for numerical differentiation; discretization of the joint probability density function of the soil properties so as to match its moments up to those of third order including the crossed moments; a discretization that matches up to some fifth-order moments; and a fine numerical integration for the marginal density function of the modulus of rigidity, discretizing the rest of the density function. The latter approach gives sufficiently accurate results for practical purposes. Effects of even moderate uncertainty about soil properties on the statistics of spectral ordinates are found to be decisive.     

Identification of an extended series of tricyclic terpanes in petroleum

A series of tricyclic terpanes from C₁₉ to C₄₅ has been identified in petroleum by gas chromatographic mass spectroscopic (GCMS) analysis. This discovery extends the previously known homologous series reported from C₁₉ to C₃₀. A method of preparation of a tricyclic terpane concentrate is described which facilitates tricyclic terpane analysis by the GCMS m/z 191 fragment. Metastable scanning GCMS is described as an additional method for characterization of the tricyclic terpanes.     

Contrast of evolution models for agricultural contaminants in ground waters by means of fuzzy logic and data mining

This work aims at contrasting, by means of a set of fuzzy logic- and data mining-based algorithms, the functioning model of a detritic aquifer undergoing overexploitation and nitrate excess input coming from strawberry and citrus intensive crops in its recharge zone. To provide researchers unskilled in data mining techniques with an easy and intuitive interpretation, the authors have developed a computer tool based on fuzzy logic that allows immediate qualitative analysis of the data contained in a data mass from the water chemical analyses, and serves as a contrast to functioning models previously proposed with classical statistics. M.L. de la Torre and J.A. Grande belongs to Water Resources and Quality Research Group. J.M. Andujar and J. Aroba belongs to Control and Robotics Research Group     

The paradigm of Circular Mining in the world: the Iberian Pyrite Belt as a potential scenario of interaction

Water is one of the receptors most affected by the impacts caused, especially in the case of mining sulphides and, to a lesser extent, of coal. Acid Mine Drainage (AMD) is the main problem associated with these mining operations, producing extremely high impacts, and in many cases irreversible impacts, until now. A new concept of mining can make this activity compatible with the environmental preservation and also to the recovery of the environment affected by the old mining operations that today are in the process of reopening. This new concept implicates the paradigm of Circular Mining as a derivative of the concept of Circular Economy, considered as a strategy that aims to reduce both the entry of materials and the production of virgin waste, closing the “loops” or economic and ecological flows of resources. The present work discusses the paradigm of Circular Mining, focused on the Iberian Pyrite Belt, one of the most paradigmatic metallogenetic regions in the world. Based on some examples, expeditious calculations show the possibility of recovering base metals as well as strategic elements from acid mine drainage, thus obtaining important economic assets.     

Hydrogeochemical and Geophysical Evaluation of the Recharge Zone of Guarani Aquifer in Municipally of Candelária,Rio Grande do Sul,Brazil

Geotechnical and Geological Engineering - A large part of the Guarani Aquifer is located in the state of Rio Grande do Sul (Brazil) and additionally possesses a recharge area located in its central...     

Geolithological and anthropogenic controls on the hydrochemistry of the Volturno river (Southern Italy)

The present work aims to study the main chemical and physical water parameters in the upper and middle Volturno river catchment (southern Italy), between the Capo Volturno springs and the confluence with the Calore river. This study makes use of morphology, geolithology, tectonic, land use, and physico‐chemical (pH, electrical conductivity, redox potential, temperature, major ions, and ²²²Rn) data for the identification of the main sources of surface and groundwaters in the Volturno catchment and of their evolution and mixing both in base flow and peak flow conditions. The study was also performed to assess whether the alteration due to potential anthropogenic contamination may hamper the identification of natural “primitive” sources of surface waters, especially in the populated and farmed plains far from the river headwaters. Our data suggest that water chemistry of this stretch of the Volturno river is dominated mainly by lithology and, only marginally, by the intense exogenous activities and that this trend is appreciable in both base flow and peak flow conditions. The proposed simple geochemical approach based on easy‐to‐sample matrices and on cost‐effective standard methods is a valuable tool to address catchment functionality especially in upland areas, where complex geologic and structural settings, heterogeneous groundwater flow, and logistical issues are the rule rather than the exception. Because the upper and middle Volturno catchment is comparable with numerous valleys of the Mediterranean area, this study could be a reference for analogous applications.     

El Niño and La Niña influence on mean river flows of southern South America in the 20th century

The influence of the El Niño Southern Oscillation (ENSO) phenomenon on monthly mean river flows of 12 rivers in the extreme south of South America in the 20th century is analysed. The original dataset of each river is divided into two subsets, i.e. warm ENSO events or El Niño, and cold ENSO events or La Niña. The elements of the subsets are composites of 24 consecutive months, from January of the year when the ENSO event begins to December of the following year. The ENSO signal is analysed by comparing the monthly mean value of each subset to the long-term monthly mean. The results reveal that, in general, monthly mean El Niño (La Niña) river flows are predominantly larger (smaller) than the long-term monthly mean in the rivers studied. The anomalies are more evident during the second half of the year in which the event starts and the first months of the following year.     

A study of heavy metal pollution in the Tinto-Odiel estuary in southwestern Spain using factor analysis

The estuary of Odiel and Tinto rivers, located on the southwestern coast of the Iberian Peninsula, receives acidic fluvial water discharges with high concentrations of sulphates and heavy metals from these rivers. In addition, a big industrial complex which efflues directly on the system is located in the same estuary. The effluents induce the presence in the estuary of high concentrations of heavy metals and phospates (nutrients). The application of factorial analysis techniques on the nutrients and heavy metal concentrations in 46 water samples taken from 32 different sampling stations located along the estuary, allows three groups of elements and compounds with a distinct origin to be determinated. So, Cu and Zn have a clear fluvial provenance, whereas PO₄ and As are clearly industrial wastes and Cl, K, Ca, Li, Rb and Sr come from the sea. From the factorial analyses we can deduce the existence of two agents controlling the behavior of the analyzed elements, which are: the tidal exchange with the open sea and the fluvial supply. Received: 20 November 1998 · Accepted: 11 August 1999     

U–Pb Geochronology of VMS mineralization in the Iberian Pyrite Belt

A geochronology study using U-Pb isotope dilution TIMS analyses of zircon has been conducted to determine the ages of volcanic-associated massive sulfide (VMS) deposits in the Iberian Pyrite Belt (IPB), the world's most prolific VMS province. Ages have been determined for host rocks to four VMS systems that span the IPB: the giant Rio Tinto and Aljustrel districts in the central region, Lagoa Salgada to the west, and Las Cruces to the east. A sample of chloritized quartz porphyritic dacite/rhyolite in the footwall of the San Dionisio massive sulfide deposit of the Rio Tinto district is 349.76ǂ.90 Ma. This is taken as the best age estimate of the mineralization in the Rio Tinto district, probably the world's largest volcanogenic massive sulfide system. Two xenocrystic zircons from the same sample yielded ²⁰⁷Pb/²⁰⁶Pb ages of 414 and 416 Ma, which provide a minimum estimate for the age of the inherited component. A biotite tonalite from the Campofrio area, 3.5 km north of the center of the Rio Tinto district, is chemically similar to the felsic host rock protolith at Rio Tinto. The Campofrio sample has an age of 346.26ǂ.81 Ma, slightly younger and outside of the 2C error for the Rio Tinto age; therefore, this phase of this intrusion was not a heat source for the hydrothermal system that formed the deposits of the Rio Tinto district. The Campofrio sample also has three zircon analyses with ²⁰⁷Pb/²⁰⁶Pb minimum ages of 534, 536, and 985 Ma, indicating inheritance from Ordovician and Neoproterozoic sources. In the Aljustrel VMS district, a U-Pb zircon age of 352.9ǃ.9 Ma characterizes the altered Green Tuff host rock of the Algares deposit, which is slightly older than the Rio Tinto age. Two zircons with ²⁰⁷Pb/²⁰⁶Pb ages of 531 and 571 Ma from this sample indicate inheritance from a Cambrian or older source. The age of mineralization at Lagoa Salgada is given by essentially identical ages of 356.21ǂ.73 and 356.4ǂ.8 Ma, for footwall and hanging wall samples, respectively. The hanging wall sample has two zircon analyses with ²⁰⁷Pb/²⁰⁶Pb ages of 464 and 466 Ma, indicating inheritance from an Ordovician or older source. The age for an altered dacite tuff sample from the hanging wall of the Las Cruces deposit is 353.97ǂ.69 Ma. One zircon analysis from the Las Cruces sample has a ²⁰⁷Pb/²⁰⁶Pb age of 1048 Ma, indicating inheritance from a Neoproterozoic source. These U-Pb ages refine the IPB geochronology provided by previous studies, and they suggest that either volcanism progressed toward the center of the IPB, or that volcanism was broadly static and the strata were progressively rifted to the margins during transtensional basin formation. The zircon inheritance provides direct evidence for Proterozoic to Ordovician sources, reflecting either basement rocks beneath the Phyllite-Quartzite Group during VMS formation in late Tournaisian times, or a Proterozoic to Ordovician detrital component in Phyllite-Quartzite Group source rocks. The presence of an older crustal component is consistent with VMS formation during rift development at a continental margin.     

Prediction of stresses and strains around model tunnels with adjacent embedded walls in overconsolidated clay

This paper presents the results of finite element analyses carried out using different constitutive models for overconsolidated clay: the Modified Cam clay model and the Three-Surface Kinematic Hardening (3-SKH) model. These analyses are evaluated against data from an extensive series of physical model tests examining the influence of an embedded wall placed near a tunnel on ground movements and tunnel stability. It is shown that for heavily overconsolidated soils reasonable predictions of both deformations and failure can be obtained from kinematic hardening models such as the 3-SKH model, which allow plastic deformation inside a Modified Cam clay state boundary surface.