Saint-André-lez-Lille, France
Saint-André-lez-Lille, France

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Shahid M.,COMSATS Institute of Information Technology | Shahid M.,National Polytechnic Institute of Toulouse | Shahid M.,CNRS Functional Ecology & Environment Laboratory | Pourrut B.,LGCgE | And 6 more authors.
Reviews of Environmental Contamination and Toxicology | Year: 2014

Environmental contamination by hazardous environmental pollutants is a widespread and increasingly serious problem confronting society, scientists, and regulators worldwide (Debenest et al. 2010; Hajeb et al. 2011; Nanthi and Bolan 2012; Shahid et al. 2013a). Among these pollutants, the heavy metals, are a loosely-defined group of elements that are similar in that they all exhibit metallic properties, and have atomic masses >20 (excluding the alkali metals) and specific gravities >5 (Rascio and Navari-Izzo 2011). This group mainly includes transition metals, some metalloids, and the lanthanides and actinides. Heavy metals can be toxic to plants, animals and humans, even at very low concentrations. Heavy metals are natural components of the earth's crust and are present in different concentrations at different sites (Shahid et al. 2012a). © 2014 Springer International Publishing Switzerland.


Shahid M.,COMSATS Institute of Information Technology | Dumat C.,National Polytechnic Institute of Toulouse | Dumat C.,CNRS Functional Ecology & Environment Laboratory | Pourrut B.,LGCgE | And 4 more authors.
Russian Journal of Plant Physiology | Year: 2015

Chemical speciation of metals in soil/solution plays an important role in determining their biogeochemical behavior in soil-plant system. The current study evaluated the influence of applied form of Pb (metal speciation) on its toxicity to metal sensitive Vicia faba L. roots. Lead was applied to young V. faba seedlings alone or chelated by organic ligands (citric acid and ethylenediaminetetraacetic acid). Plants were exposed to all treatments for 1, 4, 8, 12, and 24 h in nutrient solution, and contents of H2O2 and thiobarbituric-acid-reactive substances (TBARS) production were analyzed in V. faba roots. The results showed that Pb toxicity to V. faba roots depended on its applied chemical form and duration of exposure. Lead alone caused two burst of lipid peroxidation and H2O2 induction at 1 h and 12 h. Addition of EDTA dose-dependently inhibited Pb-induced H2O2 and TBARS production, indicating a protective role of this chelator against Pb toxicity during the first 24 h. In contrast, citric acid did not show significant effects on Pb-induced H2O2 and TBARS production, but delayed the induction of these effects. This study suggested that Pb toxicity to V. faba roots varies with Pb speciation in growth medium. © 2015, Pleiades Publishing, Ltd.


Shahid M.,COMSATS Institute of Information Technology | Pinelli E.,National Polytechnic Institute of Toulouse | Pinelli E.,CNRS Functional Ecology & Environment Laboratory | Pourrut B.,LGCgE | And 2 more authors.
Journal of Geochemical Exploration | Year: 2014

The biogeochemical behavior of metals varies with their chemical speciation. The present study evaluated the effect of metal speciation on lead-induced oxidative stress to Vicia faba leaves. Lead was applied to V. faba plants in the form of lead nitrate alone or chelated by citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) in hydroponic conditions. The exposure time for all the treatments was 1, 4, 8, 12 and 24. h. The activation of antioxidant enzymes in V. faba leaves varies with Pb speciation and duration of exposure. Application of Pb alone increased the activities of superoxide dismutases (SOD), guaiacol peroxidase (GPOX), ascorbate peroxidase (APX) and glutathione reductase (GR) while reducing that of catalase (CAT) in V. faba leaves. Application of EDTA dose dependently alleviated the Pb-induced activation of SOD, APX, GPOX and GR, and depression of CAT by decreasing Pb accumulation in V. faba leaves. By contrast, CA had no effect on Pb accumulation and antioxidant enzyme activities except that the activation of SOD, APX, GPOX and GR, and reduction of CAT was delayed. The results showed that the physiological responses of V. faba leaves to Pb toxicity vary with its chemical speciation. Therefore, it is proposed that metal speciation must be given consideration in risk assessment and remediation studies. © 2014 Elsevier B.V.


Shahid M.,COMSATS Institute of Information Technology | Dumat C.,National Polytechnic Institute of Toulouse | Dumat C.,CNRS Functional Ecology & Environment Laboratory | Pourrut B.,LGCgE | And 3 more authors.
Journal of Geochemical Exploration | Year: 2014

Lead is a highly toxic heavy metal, but its putative toxicity with respect to its speciation remains to unveil. In this study, Pb-induced toxicity to Vicia faba pigment contents was assessed against Pb speciation and accumulation. After a culture period of three weeks, V. faba seedlings were exposed to 5. μM of lead nitrate alone or chelated by citric acid (CA) or ethylenediaminetetraacetic acid (EDTA). The plants were treated for 1, 4, 8, 12 and 24. h in nutrient solution. Exposure to Pb-5 caused increased production of reactive oxygen species, lipid peroxidation and decrease in V. faba chlorophyll contents during 24. h. Lead-induced oxidative stress and toxicity to chlorophyll contents varied with the speciation of Pb. Addition of EDTA to Pb solution alleviated Pb-induced oxidative stress and toxicity to V. faba pigments by decreasing Pb accumulation in V. faba leaves. However, addition of citric acid to Pb did not affect Pb accumulation or toxicity to V. faba leaves. It is proposed that metal speciation plays an important role in Pb toxicity to V. faba pigment. Moreover, organic ligands vary greatly in terms of their ability to modify Pb phytoaccumulation and toxicity. © 2014 Elsevier B.V.


Shahid M.,National Polytechnic Institute of Toulouse | Shahid M.,CNRS Functional Ecology & Environment Laboratory | Shahid M.,COMSATS Institute of Information Technology | Dumat C.,National Polytechnic Institute of Toulouse | And 8 more authors.
Journal of Soils and Sediments | Year: 2014

Purpose: In spite of substantial advancement in recent past, the role of metal speciation in assessing biogeochemical behaviour of Pb is still topical. Organic ligands are capable to modify Pb speciation in nutrient/soil solution and in turn its soil-plant transfer and toxicity. In this sense, the main objective of this study was to evaluate the effect of organic ligands on Pb-induced oxidative stress to Vicia faba roots. Materials and methods: V. faba seedlings grown to controlled hydroponic system were treated with 5 μM Pb as lead nitrate in the presence and absence of organic ligands viz ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) for 1, 4, 8, 12, and 24 h. The chemical speciation of Pb (percent free and chelated Pb) in nutrient solution in the presence and absence of organic ligands was calculated using Visual Minteq speciation model. The effect of chemical speciation on Pb-induced oxidative stress to V. faba roots was investigated using plant enzymatic antioxidative system [superoxide dismutases (SOD), guaiacol peroxidise (GPX), ascorbate peroxidase (APX), glutathione reductase (GR), and catalase (CAT)]. The antioxidant enzymes activities were determined using ultraviolet spectrophotometer. Results and discussion: The activities of SOD, GPX, APX, and GR significantly increased whereas that of CAT decreased in V. faba roots under Pb alone treatment. Lead-induced increase/decrease in antioxidant enzymes activities was not linear but varies with treatment exposure time. EDTA dose dependently inhibited Pb-induced changes in antioxidant enzymes activities. However, CA did not cause any significant change in Pb-induced variation in antioxidant enzymes activities, but delayed or slightly reduced the Pb effect. Conclusions: The present study suggested that physiological responses of V. faba roots to Pb toxicity vary with applied Pb form and duration of exposure. EDTA can inhibit Pb-induced toxicity to V. faba seedlings by forming stable Pb-EDTA complexes due to its high binding strength for Pb. However, CA had no effect on Pb-induced toxicity to V. faba roots due to weak complexation with Pb. © 2013 Springer-Verlag Berlin Heidelberg.


Kimbonguila Manounou A.,LGCgE | Remond S.,University of Lille Nord de France
Physica A: Statistical Mechanics and its Applications | Year: 2014

The fragmentation and restructuring under shear of agglomerates of fine mineral particles are studied with the Distinct Element Method. The model used takes into account contact forces, van der Waals forces, and hydrodynamic forces computed with the free-draining approximation. A loose initial agglomerate is submitted to a constant shear rate until reaching a quasi-stationary state, where the number, size and structure of fragment of agglomerates can be considered as constant. The influence of shear stress and size of particles on the characteristics of agglomerates at equilibrium is studied. Fragmentation is controlled by a non-dimensional number, depending on the radius of the particles, shear rate and maximal adhesion force. © 2014 Elsevier B.V. All rights reserved.


Helnan-Moussa B.,LGCgE | Vanhove Y.,LGCgE | Wirquin E.,LGCgE
Advances in Cement Research | Year: 2013

A semi-empirical procedure is proposed to obtain a new insight into the structural breakdown of fresh cement pastes by using different nature and the dosages of viscosity-modifying admixture (VMA). For this approach, tests were conducted with two types of VMA at 218C. The protocol used is based on a down stepwise shear rate sequence after shearing the material at a constant high shear rate and at a variable preshearing time. A destructuration potential K is obtained by the analysis of the breakdown area for each preshearing time. Results suggest different critical dosages of VMA. A maximum value of dosage of VMA is obtained from the results. Beyond this value, the tridimensional networks formed by the cement pastes are highly structured and consequently more difficult to deform by shearing.


Arab A.,University of Hassiba Ben Bouali Chlef | Belkhatir M.,University of Hassiba Ben Bouali Chlef | Sadek M.,LGCgE
Geotechnical and Geological Engineering | Year: 2016

This paper presents a laboratory study of the influence of saturation degree on the liquefaction potential of sand. The study is based on drained, undrained monotonic and cyclic triaxial tests. Tests were conducted on a medium dense Hostun RF sand (France) with an initial relative density Dr = 4, 50, 64 and 78 % and the coefficient of Skempton ranging between 0.95 (saturated) and 0.25. For all Skempton’s coefficient B values, the tests were carried out for different loading levels. The monotonic tests show that an increase in the Skempton’s coefficient B leads to a reduction of liquefaction resistance. The decrement of the coefficient of saturation B does not affect the instability and steady state lines. The test results indicate that the liquefaction resistance increases with the decrease of Skempton’s coefficient B. For the high level of loading (RCC = 0.5), the number required to cause liquefaction varied little with the Skempton’s coefficient B (Nc = 9, 10 and 11 for B = 0.67, 0.36 and 0.25 respectively). For the low level (RCC < 0.40), the number of cycles needed for liquefaction increases susceptibly with the reduction of the coefficient of Skempton (B). A simple mathematical relation has been suggested to correlate the liquefaction resistance with the coefficient of Skempton B. © 2015, Springer International Publishing Switzerland.

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