Trace element contamination in the mine-affected stream sediments of Oued Rarai in north-western Tunisia. A river basin scale assessment

High-quality and accurate environmental investigations are essential for the evaluation of contamination and subsequent decision-making processes. A combination of environmental geochemical indices, multivariate analyses and geographic information system approach was successfully used to assess contamination status and source apportionment of trace elements (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, V and Zn) in surface stream sediments from the Oued Rarai basin in north-western Tunisia, containing various metal and metalloid ores. The contamination level reported in this study indicates a non-negligible potential ecological risk, mainly related to sediment transport along the river. Antimony (concentrations ranged from 0.02 to 297 mg kg−1 and Igeo > 5), arsenic (from 0.5 to 1490 mg kg−1 and Igeo > 5), lead (from 2.9 to 5150 mg kg−1 and Igeo > 5) mercury (from 0.05 to 54.4 mg kg−1 and Igeo > 5) and silver (from 0.05 to 9.4 mg kg−1 and Igeo > 5) showed the most crucial contamination. Besides, potential ecological risk index values were maximum for arsenic with a median of 302, indicating a very high to serious ecological risk (> 160). Results from correlation analysis and principal component analysis revealed three main geochemical associations related to lithologic, tectonic and anthropogenic sources. V, Cr and Cu mainly originated from natural bedrock and soil. Ag and Cd were more controlled by both natural and mining enrichments. Mercury and Pb were mostly influenced by the ancient ore-related activities at the Oued Rarai site and north-east–south-west trending faults. Finally, Sb, As, Ni and Zn were largely controlled by the siliciclastic continental Neogene sequences. Finally, the physical and chemical dynamics of the watershed system, lithological properties, mineralisation, tectonic settings and mobilisation of subsurface sediments largely controlled both concentrations and spatial patterns of trace elements in the study basin. These results need to be considered in the strategies of suitable environmental management at former and current mining sites in north-western Tunisia

Combined Heat and Mass Transfer during Condensation of Vapours Mixture and Non-Condensable Gas in a Vertical Tube

The problem of laminar film condensation from binary vapours mixture with the presence of non-condensable gas (air) flowing in a vertical tube is numerically investigated. The set of the non-linear parabolic equations expressing the mass conservation, momentum, energy, and species diffusion in both phases with the boundary conditions are resolved by using a finite difference numerical scheme. A comparative study between the results obtained for three cases (water-ethanol-air, water-methanol-air, and ethanol-methanol-air) under the same conditions is made. The impact of varying the wall temperature, the inlet vapour mass fractions, and the inlet liquid mass flow rate on the conjugate the heat and mass transfer during the condensation of the studied mixtures are examined. It is found that the condensation of water-methanol-air corresponds to a higher latent heat flux QL2 and accumulated condensation rate Mr2 when compared with water-ethanol-air and ethanol-methanol-air. Moreover, the nature of the fluid plays an important role in the heat and mass exchanges

Synchronization of fractional order chaotic systems

The chaotic dynamics of fractional order systems begin to attract much attentions in recent years. In this brief report, we study the master-slave synchronization of fractional order chaotic systems. It is shown that fractional order chaotic systems can also be synchronized.Comment: 3 pages, 5 figure

Gas flow humidification enhancement by evaporating seawater liquid film

Dans ce présent travail nous étudions l'humidification d'un flux d'air dans un procédé de dessalement à travers l'évaporation du film liquide tout en considérant l'eau pure et l'eau de mer. Pour atteindre les objectifs, une méthode implicite de différence finie est utilisée pour résoudre les équations gouvernantes couplées dans les phases liquide et gazeuse. L'influence des conditions d'entrée du film liquide, y compris la salinité, sur l'humidification du flux d'air dans un tube vertical est étudiée

A BIM-based theoretical framework for the integration of the asset End-of-Life phase

Due to the migration of industry from the use of traditional 2D CAD tools to Building Information Modelling (BIM) process, and the growing awareness of Construction and Demolition (C&D) waste issues, researchers are interested in compiling the use of BIM for C&D Waste issues. BIM is commonly used for the Design, Construction and Maintenance phases of an asset; however, the use of BIM for the End-of-Life management is still in its infancy. This paper proposes to reconsider the asset lifecycle by incorporating a sustainable End-of-Life, as a phase, in BIM context. Recommendations are given to push the BIM potential up to the asset End-of-Life management. Based on the results of a literature review assessing the current use of BIM for the asset End-of-Life, a conceptual framework was drawn. A set of eleven stakeholders, involved in the asset lifecycle, from inception to deconstruction were interviewed to improve the conceptual framework. The research reveals the impacts and barriers for the integration of the deconstruction phase into the asset lifecycle. Consequently, a theoretical framework for the asset lifecycle from inception to deconstruction in BIM environment is created to change the linear system to a circular economy.Peer reviewe

Los emigrantes cualificados del Magreb

This paper addresses the “brain drain” side of the contemporary migration of peoples from the Magreb region to the European Union and, more specifically to France. The measurement device is the documentation published by UNESCO and EUROSTAT on foreign college level students in EU countries. Magreb countries are well above the world average in terms of university students abroad over total university students. This fact has both positive and negative consequences for the socioeconomic development of the sending countries. The paper analyses several of them, focusing on the advantages of transnational networks. The analysis is taken from a dual point of view, European and North African as well. Discrepancies are not erased, since the authors believe that there is not overall consensus on the outcomes of the “brain drain” process that is taking place since several decades by now.También en el Magreb se produce una fuga de cerebros hacia países más desarrollados. En este artículo analizamos la componente europea de ese flujo; más concretamente, el establecimiento de graduados magrebíes en la Unión Europea y, más específicamente, en Francia. Utilizamos como indicadores las estadísticas que la UNESCO y EUROSTAT publican sobre estudiantes extranjeros universitarios en los países de la Unión Europea. Por encima de la media mundial, el Magreb destaca por su proporción de estudiantes en el extranjero sobre total de población estudiantil. Esta situación desemboca en una pérdida considerable de cápital humano magrebí, por el establecimiento de muchos de sus graduados universitarios en los países desarrollados donde cursa sus estudios superiores. En el artículo se analizan también las ventajas de este tipo de situaciones para los países de origen, que se benefician del establecimiento de redes transnacionales de individuos muy capacitados. El punto de vista del análisis es dual, a la vez europeo y norteafricano, subrayando claramente las diferencias que existen entre los dos, más allá de un consenso banal

SEIS: Insight's Seismic Experiment for Internal Structure of Mars.

By the end of 2018, 42 years after the landing of the two Viking seismometers on Mars, InSight will deploy onto Mars' surface the SEIS (Seismic Experiment for Internal Structure) instrument; a six-axes seismometer equipped with both a long-period three-axes Very Broad Band (VBB) instrument and a three-axes short-period (SP) instrument. These six sensors will cover a broad range of the seismic bandwidth, from 0.01 Hz to 50 Hz, with possible extension to longer periods. Data will be transmitted in the form of three continuous VBB components at 2 sample per second (sps), an estimation of the short period energy content from the SP at 1 sps and a continuous compound VBB/SP vertical axis at 10 sps. The continuous streams will be augmented by requested event data with sample rates from 20 to 100 sps. SEIS will improve upon the existing resolution of Viking's Mars seismic monitoring by a factor of ∼ 2500 at 1 Hz and ∼ 200 000 at 0.1 Hz. An additional major improvement is that, contrary to Viking, the seismometers will be deployed via a robotic arm directly onto Mars' surface and will be protected against temperature and wind by highly efficient thermal and wind shielding. Based on existing knowledge of Mars, it is reasonable to infer a moment magnitude detection threshold of M w ∼ 3 at 40 ∘ epicentral distance and a potential to detect several tens of quakes and about five impacts per year. In this paper, we first describe the science goals of the experiment and the rationale used to define its requirements. We then provide a detailed description of the hardware, from the sensors to the deployment system and associated performance, including transfer functions of the seismic sensors and temperature sensors. We conclude by describing the experiment ground segment, including data processing services, outreach and education networks and provide a description of the format to be used for future data distribution.Electronic supplementary materialThe online version of this article (10.1007/s11214-018-0574-6) contains supplementary material, which is available to authorized users

SEIS: Insight’s Seismic Experiment for Internal Structure of Mars

By the end of 2018, 42 years after the landing of the two Viking seismometers on Mars, InSight will deploy onto Mars’ surface the SEIS (Seismic Experiment for Internal Structure) instrument; a six-axes seismometer equipped with both a long-period three-axes Very Broad Band (VBB) instrument and a three-axes short-period (SP) instrument. These six sensors will cover a broad range of the seismic bandwidth, from 0.01 Hz to 50 Hz, with possible extension to longer periods. Data will be transmitted in the form of three continuous VBB components at 2 sample per second (sps), an estimation of the short period energy content from the SP at 1 sps and a continuous compound VBB/SP vertical axis at 10 sps. The continuous streams will be augmented by requested event data with sample rates from 20 to 100 sps. SEIS will improve upon the existing resolution of Viking’s Mars seismic monitoring by a factor of ∼ 2500 at 1 Hz and ∼ 200 000 at 0.1 Hz. An additional major improvement is that, contrary to Viking, the seismometers will be deployed via a robotic arm directly onto Mars’ surface and will be protected against temperature and wind by highly efficient thermal and wind shielding. Based on existing knowledge of Mars, it is reasonable to infer a moment magnitude detection threshold of Mw ∼ 3 at 40◦ epicentral distance and a potential to detect several tens of quakes and about five impacts per year. In this paper, we first describe the science goals of the experiment and the rationale used to define its requirements. We then provide a detailed description of the hardware, from the sensors to the deployment system and associated performance, including transfer functions of the seismic sensors and temperature sensors. We conclude by describing the experiment ground segment, including data processing services, outreach and education networks and provide a description of the format to be used for future data distribution