Spatial and temporal variability of groundwater quality of an Algerian aquifer: the case of Soummam Wadi

ABSTRACT

Five-year monitoring of physicochemical parameters was performed with two campaigns in low and high water periods of the Lower Soummam catchment. Data from 18 wells were processed by multivariate statistical tools in order to identify the principal factors influencing groundwater chemistry. Two matrices of 14 and 8 physicochemical parameters with 18 groundwater samples collected in wells were obtained. The correlation matrix showed strong associations between nine variables: K⁺, Ca²⁺, Na⁺, SO₄^2?, Cl^?, Mg²⁺, NO₂^?, Zn²⁺ and Sr²⁺. Principal component analysis and factor analysis showed that the cumulated variance of high and low water periods was of 83.19% and 78.55%, respectively. The variables assigned to the mineralization effect or to pollution indicators were presented by the factor analysis. The bivariate plots confirmed a mineralization model, ascribed to dissolution of geological materials, and to high levels of saline contamination attributed to leakages from sanitary systems. They also showed an increase “upstream to downstream” of the mineralization, visualization of temporal variations, and a dilution process identification of the natural mineralization during the recharge of the aquifer.

EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR X. Chen     

Reionization and the Cosmic Dawn with the Square Kilometre Array

The Square Kilometre Array (SKA) will have a low frequency component (SKA-low) which has as one of its main science goals the study of the redshifted 21 cm line from the earliest phases of star and galaxy formation in the Universe. This 21 cm signal provides a new and unique window both on the time of the formation of the first stars and accreting black holes and the subsequent period of substantial ionization of the intergalactic medium. The signal will teach us fundamental new things about the earliest phases of structure formation, cosmology and even has the potential to lead to the discovery of new physical phenomena. Here we present a white paper with an overview of the science questions that SKA-low can address, how we plan to tackle these questions and what this implies for the basic design of the telescope.     

L’analyse des surfaces enveloppes appliquée à l’étude morpho-structurale de l’est de la France

Résumén

Dans certaines régions où les sédiments récents (plio-quaternaires) sont rares ou inutilisables comme enregistreurs de déformations, seule l’analyse morpho-strcturale peut mettre en évidence des indices de néotectonique. Deux types d’objets morphologiques se révèlent particulièrement utiles : les surfaces (d’érosion et de comblement) et le réseau hydrographique. Leur prise en compte et leur analyse s’effectuent essentiellement à partir des cartes topographiques à différentes échelles (de 1/50 000 à 1/500 000).

* La démarche est la suivante: 1 – Des traitements appropriés sont développés, mettant en évidence des discontinuités et des anomalies au sein des surfaces enveloppes et du réseau hydrographiques;

2 – Ces discontinuités sont analysées puis interprétées afin de déterminer les causes de leur existence dans le cadre d’un modèle d’évolution du relief qui tient compte de facteurs internes (la lithologie, la structure), et de facteurs externes (le climat, la végétation et les actions humaines);

3 – Des travaux de terrain confirment et précisent les caractéristiques de ces facteurs (nature et quantification de la déformation : âge. amplitude, sens des mouvements).

* Les principaux résultats de cette démarche appliquée à l’Kst du Bassin parisien sont les suivants: 1 – Les cuestas orientales du Bassin parisien apparaissent structurées par des accidents NK-SW (prolongement du fossé de Sarre Nahe) et NNW-SSK ( Argonne-Bar-le-Due);

2 – Les discontinuités morpho-structurales sont localisées et caractérisées par des mouvements récents.

     

A one‐dimensional process‐based approach to study reservoir sediment dynamics during management operations

A comprehensive understanding of the dynamics of erosion and sedimentation in reservoirs under different management conditions is required to anticipate sedimentation issues and implement effective sediment management strategies. This paper describes a unique approach combining fluvial geomorphology tools and morphodynamic modeling for analyzing the sediment dynamics of an elongated hydropower reservoir subjected to management operations: the Génissiat Reservoir on the Rhône River. Functional sub‐reaches representative of the reservoir morphodynamics were delineated by adapting natural river segmentation methods to elongated reservoirs. The segmentation revealed the link between the spatial and temporal reservoir changes and the variability of longitudinal flow conditions during reservoir management operations. An innovative modeling strategy, incorporating the reservoir segmentation into two sediment transport codes, was implemented to simulate the dynamics of erosion and sedimentation at the reach scale during historic events. One code used a bedload approach, based on the Exner equation with a transport capacity formula, and the other used a suspended load approach based on the advection–dispersion equation. This strategy provided a fair quantification of the dynamics of erosion and sedimentation at the reach scale during different management operations. This study showed that the reservoir morphodynamics is controlled by bedload transport in upper reaches, graded suspended load transport of sand in middle reaches and suspended load transport of fine sediments in lower reaches. Eventually, it allowed a better understanding of the impact of dam management on sediment dynamics. Copyright © 2017 John Wiley & Sons, Ltd.     

Regional VS30 model for the St. Lawrence Lowlands,Eastern Canada

Shear-wave velocity of the top 30?m, V_S30, is commonly used for prediction of the seismic site response. This paper presents development, validation and uncertainty assessment of a regional V_S30 model based on a combination of simplified 3D geology and statistically representative velocity values. Results identify soft marine sediments in deep sedimentary basins as zones most susceptible to seismic shaking. Compared to the available urban-scale seismic zonation studies, the regional model showed a success rate of roughly 64% in predicting local site category. The standard deviation was in average 30% of the expected V_S30 value.     

Putting the principles of the Sustainable Livelihoods Approach into fisheries development policy and practice

The Sustainable Livelihoods Approach (SLA) combines a conceptual framework with a set of operational principles to provide guidance on policy formulation and development practice. The SLA has been widely used in coastal and fisheries development research and has informed the design of development programmes but experience of operationalising it remains largely undocumented. In the Sustainable Fisheries Livelihoods Programme, which involves 25 West African countries, the SLA has helped to align fisheries policy with wider poverty reduction initiatives and to identify means of contributing to poverty reduction that do not directly increase pressure on fully or over-exploited fish resources.     

Phase changes and thermodynamic properties of CaTiO3. Spectroscopic data,vibrational modelling and some insights on the properties of MgSiO3 perovskite

The effect of pressure (up to 21 GPa at room temperature) and temperature (up to 1570 K at room pressure) on the Raman spectrum of CaTiO₃ is presented. No significant changes, which could be attributed to a major structural change, are observed in the spectra up to 22 GPa. The pressure shifts of the Raman modes can be related to a significant compression of the Ti-O bond. Discontinuous changes in the spectra upon heating may be related to phase changes observed by calorimetry and X-ray diffraction. The important temperature shifts of some low-frequency modes can be related to an increase in the Ti-O-Ti angle in agreement with the X-ray data showing a decrease of the structural distortion with increasing temperature. These data are compared to those available for MgSiO₃-perovskite and show that CaTiO₃ is a good structural analogue for MgSiO₃-perovskite. The present spectroscopic data are used to calculate the specific heat and entropy of CaTiO₃. The role of the low frequency modes in the calculations is emphasized. Good agreement is observed between calculated and experimentally determined values in the 0–1300 K temperature range. A similarly defined model is proposed for MgSiO₃-perovskite. It is found that the entropy lies between 57 and 64 J/mol/K at 298 K and between 190 and 200 J/mol/K at 1000 K in agreement with the values inferred from experimental equilibrium data. Finally we briefly discuss the values of the Grüneisen parameters of both perovskites inferred from macroscopic and microscopic data.