Résumé : The slides were taken on collecting trips sponsored by the William L. Bryant Foundation, where books, music and art indigenous to the regions were gathered. The are organized by geographical location.
Pictured is the metal frame of a carnival costume’s bodice decorated with green and beige sequin. The costume is being made in a yard outside in Trindid. Slide labeled Trin. 15.
Trinidad and Tobago -- South America -- Trinidad
Trinidad and Tobago -- Caribbean region -- Trinidad

Droits : All rights to images are held by the respective holding institution. This image is posted publicly for non-profit educational uses, excluding printed publication. For permission to reproduce images and/or for copyright information contact Special Collections & University Archives, University of Central Florida Libraries, Orlando, FL 32816 phone (407) 823-2576, email: speccoll@mail.ucf.edu
CFM1972_01a
http://ufdc.ufl.edu/AA00031209/00001

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Inorganic arsenic is a toxic environmental contaminant to which humans are mainly exposed through drinking water. This metalloid impairs functions of several key immune cells. Particularly, it reduces IL-2 secretion and proliferation of blood peripheral mononuclear cells stimulated by lectins that, however, do not mimic physiological T cell activation. The present study used isolated human T cells activated, in a more physiological manner, through stimulation with CD3/CD28 antibodies, to carefully analyze the impact of arsenic on T cell proliferation and cytokine expression. We demonstrate that non cytotoxic concentrations of sodium arsenite (As(III), 0.25-2μM) significantly reduce T cell proliferation by increasing the percentage of non dividing cells blocked in G1 phase and by preventing cyclin D3 and CDC25A expression. They also markedly, although not totally, reduces IL-2 expression at both mRNA and protein levels; however, metalloid-dependent inhibition of T cells could not be reversed by addition of recombinant IL-2. In addition, As(III) markedly reduces secretion of interferon-γ without impairing that of IL-4 and IL-13; it also decreases interferon-γ mRNA levels but increases those of IL-13. Finally, simultaneously to its immune effects, As(III) rapidly and potently increases expression of the redox-sensitive genes HMOX1, NQO1 and GCLM in activated T cells without altering the levels of reactive oxygen species. In conclusion, our results demonstrate that As(III) inhibits T cell proliferation, independently of IL-2, and alters the Th balance of cytokines secreted by co-stimulated T cells which thus constitute direct targets of this major environmental contaminant.
ISSN: 0300-483X

inserm-00872848
http://www.hal.inserm.fr/inserm-00872848
DOI : 10.1016/j.tox.2012.05.025
PUBMED : 22683347

Éditeur(s) : HAL CCSD Institute of Electrical and Electronics Engineers
Résumé : International audience
An effective solution for increasing the exposure uniformity and efficiency of biological samples in in vitro bioelectromagnetic experiments at 60 GHz is proposed by introducing a novel choke ring antenna (CRA). The CRA is optimized to provide a uniform exposure of samples, whose dimensions are equivalent to those of a standard 35-mm Petri dish, positioned close to the antenna aperture, i.e., 10-20 wavelengths. The antenna prototype is fabricated in metallized foam. The realized exposure efficiency of the sample exceeds 55% (if estimated for an exposure uniformity better than - 0.5 dB). To validate the numerical results, the field intensity profiles on the surface of a high-water-content phantom have been experimentally obtained using a high-resolution infrared camera. Compared to the standard open-ended waveguide and horn antennas, typically used for millimeter-wave dosimetry, a twofold advantage of the proposed CRA is demonstrated, namely, the improvement of the exposure efficiency by a factor of 1.5 to 2 with a simultaneous reduction of the exposure distance by a factor of 8-2, respectively, depending on the type of the reference antenna. These advantages make the proposed CRA an excellent candidate for 60-GHz short-range exposure systems for in vitro bioelectromagnetic studies.
ISSN: 0018-9480

hal-00874349
https://hal.archives-ouvertes.fr/hal-00874349
DOI : 10.1109/TMTT.2013.2255619

Éditeur(s) : HAL CCSD
Résumé : Inorganic arsenic is an environmental human carcinogen, but is also studied these days because of its potential effectiveness in curing chronic inflammatory disease. Indeed, this metalloid possesses immunosuppressive properties which can dysregulate physiological mechanisms involved in immune defense, or reduce inflammation associated with those inflammatory diseases. Inorganic arsenic is known mainly to alter functions of T cells and macrophages. However, it is unknown whether arsenic targets dendritic cells (DCs). Yet, this antigen presenting cells plays a major role in the immunosurveillance, and is involved in the physiopathology of chronic inflammatory diseases. So, the aim of my thesis work was to study the effects of inorganic arsenic on in vitro differenciation and maturation of dendritic cells from human monocytes. Our results mainly shows that concentrations corresponding to those measured in environmentally exposed people, inhibits DCs secretion of proinflammatory cytokines, which plays a major role in activation and polarization of T cells. Particularly, arsenic strongly impairs expression and secretion of interleukine 12 (IL-12) by an underlying molecular mechanism involving Nrf2. Finally, this work shows that inorganic arsenic has immunosuppressive properties on the physiology in vitro of human dendritic cells. Immunotoxicity may then contribute to the metalloid toxicity in environmentally exposed people. This element could be taken into account when determining arsenic effects in curing some chronic inflammatory diseases.
L’arsenic inorganique est un contaminant environnemental, cancérogène pour l’homme, mais également un métalloïde étudié, aujourd’hui, dans le traitement de maladies inflammatoires chroniques. Il possède des propriétés immunosuppressives pouvant déréguler les mécanismes physiologiques de défense ou bloquer l’exacerbation de réponses inflammatoires chroniques. L’arsenic inorganique altère principalement les fonctions des lymphocytes T et des macrophages. En revanche, l’impact du métalloïde sur la physiologie des cellules dendritiques (DCs) est peu connu. Pourtant, ces cellules présentatrices d’antigène jouent un rôle fondamental dans les processus d’immunosurveillance et sont très impliquées dans la physiopathologie des maladies inflammatoires chroniques. Dans ce contexte, les objectifs de mon travail de thèse étaient d’étudier les effets de l’arsenic inorganique sur la différenciation et la maturation in vitro de DCs générées à partir de monocytes humains. Nos résultats démontrent principalement que des concentrations de métalloïde, compatibles avec les taux plasmatiques d’arsenic mesurés chez les individus exposés, répriment la capacité des DCs à sécréter différentes cytokines pro-inflammatoires jouant un rôle essentiel dans l’activation et la polarisation des lymphocytes T. En particulier, l’arsenic inhibe l’expression et la sécrétion de l’interleukine-12 par un mécanisme moléculaire impliquant le facteur de transcription Nrf2. Au total, ces travaux de thèse démontrent que l’arsenic inorganique possède des propriétés immunosuppressives sur la physiologie in vitro des DCs humaines. Cette immunotoxicité pourrait contribuer à la toxicité du métalloïde chez l’homme exposé par voie environnementale, et être prise en compte pour déterminer les effets de l’arsenic dans le traitement de certaines maladies inflammatoires chroniques
https://tel.archives-ouvertes.fr/tel-01135887

NNT : 2013REN1B013
tel-01135887
https://tel.archives-ouvertes.fr/tel-01135887
https://tel.archives-ouvertes.fr/tel-01135887/document
https://tel.archives-ouvertes.fr/tel-01135887/file/pdf2star-1392896105-Th--se-M--linda-Macoch2.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Orogenic lherzolites exhibit a specific (although reproducible) platinum-group element signature characterized by slight positive deviations of Pd/Ir, Rh/Ir and Ru/Ir ratios from the canonical chondritic model. Such a signature was alternatively considered to be a compositional feature of the primitive upper mantle or resulting from sulfide melt addition by refertilisation reactions in the continental lithosphere. To shed additional light on this conundrum, the distribution of PGE in FON B 93, an unserpentinized, fertile (3.24% Al2O3) orogenic lherzolite (French Pyrenees) used as in-house standard by our group, has been studied to different scales, from the bulk rock to trace minerals. In addition to new ICPMS analyses after separation into Nis and Te coprecipitation, its whole-rock PGE concentrations were redetermined by three different laboratories using very precise ID-ICP-MS methods after digestion of the sample in Carius tube at T=250 degrees C and 320 degrees C or in high-pressure asher (HPA-S). The four methods produce reproducible Ru, Rh and Pd contents (7.1 +/- 0.18 ppb; 1.43 +/- 0.05 ppb; 7.1 +/- 0.30 ppb) whereas the non-ID NiS-fire assay method underestimates the Os and Ir concentrations by c.a. 10 and 15% compared to ID-ICP-MS analyses (4.40 +/- 0.07 and 4.00 +/- 0.17 ppb, respectively). Platinum was the most difficult to analyse. If performed on powder aliquots smaller than 3 g, the ID-ICP-MS analyses generate strong nugget effects while the non-ID NiS-fire assay method yields statistically lower (but highly reproducible) Pt concentrations (6.92 +/- 0.26 ppb). These features reflect the strong partitioning of Pt into trace phases that SEM and laser ablation-ICP-MS analyses on thin sections identify as both high-temperature Pt-Ir-Os alloys and Pt-(Pd) tellurides of likely subsolidus origin; ten to fifteen grains ranging in maximum dimension from a few micrometres to a few hundreds of nanometers, were identified by standard polished thin section. LA-ICP-MS data on base metal sulfides (25 grains analysed), coupled with the whole-rock S concentration (277 +/- 10 ppm) and modal composition of the BMS (90% pentlandite+accessory pyrite and secondary pyrrhotite + 10% chalcopyrite) allowed the contribution of the BMS phase to the PGE budget of FON B 93 to be estimated. Except Pt that exhibits a 95% deficit in the BMS phase, the PGE concentrations measured by ID-ICP-MS can be balanced by BMS while Al-spinel is a negligible contributor, accounting for less than 0.5% of the Ru budget. The occurrence of Pt in trace phases may bias the whole-rock Pt concentrations because 1) mechanical collection of Pt-rich trace phases remains problematic with the Nis button, and 2) Pt-Ir-Os alloys may be prone to digestion problems in conventional Carius tube procedures. Since they could be stable at mantle depth, such refractory alloys that contain Os and Ir may also have enhanced the heavy PGEs/light PGEs fractionation. Our observations likely pertain to orogenic lherzolites as a whole because BMS assemblages in these mantle rocks record evolution at low sulfur fugacity, which prevents Pt-Ir-Os alloy from entering the Mss in the mantle; moreover, at subsolidus temperature, pentlandite, the major BMS, cannot accommodate 0 valence state Pt.
ISSN: 0009-2541

hal-00411486
https://hal.archives-ouvertes.fr/hal-00411486
DOI : 10.1016/j.chemgeo.2007.06.030

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Numerous field studies highlighted the capacities of marine sponges to bioaccumulate trace elements and assessed their potential as biomonitors of the marine environment. Experimental works demonstrated that dissolved metals and radionuclides can be taken up directly by sponge tissues but, to the best of our knowledge, little is known on the contribution of the dietary pathway through the consumption of contaminated bacteria considered as one of the trophic source in sponge diet. Objectives of this work are to study trophic transfer of radiotracers 110mAg, 241Am, 109Cd, 57Co, 134Cs, 54Mn and 65Zn from the marine bacteria Pseudomonas stutzeri to the Mediterranean sponges Aplysina cavernicola and Ircinia oros. P. stutzeri efficiently bioaccumulated trace elements in our culture experimental conditions with CF comprised between 105 and 107 after 48 hours of growth in radiolabeled medium. When fed with these radiolabelled bacteria, A. cavernicola took up around 60% of radiotracers accumulated in trophic source except 134Cs for which only 8% has been transferred from bacteria to sponge. Contrasting to this, I. oros retained only 7% of 110mAg, 109Cd and 65Zn counted in bacteria, but retained 2-fold longer accumulated metals in its tissues. The sponge inter-specific differences of accumulation and depuration following a trophic exposure are discussed with respect to the structure and the clearance capacities of each species.
ISSN: 0045-6535

hal-01217273
https://hal.archives-ouvertes.fr/hal-01217273
https://hal.archives-ouvertes.fr/hal-01217273/document
https://hal.archives-ouvertes.fr/hal-01217273/file/Pub%20Bacteria%20CHEM_HAL.pdf
DOI : 10.1016/j.chemosphere.2015.10.046

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
The mantle and continental crust--Earth's main silicate reservoirs--have a lead isotope composition that is too radiogenic to have evolved from primitive Solar System material over 4.57 billion years1. To account for this imbalance, it has been suggested that unradiogenic lead may have partitioned into the metallic core2, 3, 4 or lower continental crust5. Alternatively, radiogenic lead could have been added to Earth later by meteorite impacts6. Unradiogenic lead was discovered in fragments of mantle rocks exhumed in the Horoman massif, Japan, implying that the mantle itself may provide a complementary reservoir of unradiogenic lead7. However, it is unclear why this unradiogenic component is not sampled by the melting that generates oceanic basalts8. Here we present double-spike lead isotope data for abyssal peridotite rocks, considered to represent suboceanic mantle, exposed on the Atlantic Ocean floor. We find that sulphides dated at about 1.83 billion years old and trapped as inclusions in silicate minerals preserve extremely unradiogenic lead isotope compositions. This unradiogenic lead could have been prevented from adding significantly to oceanic basalts if either the silicates shield the sulphide inclusions or if the sulphides reside in refractory mantle rocks that are rarely sampled during melting. We conclude that the lead isotope composition of the silicate Earth could be largely balanced by unradiogenic lead in sulphide in the mantle.
ISSN: 1752-0894

hal-00795575
https://hal.archives-ouvertes.fr/hal-00795575
DOI : 10.1038/ngeo1531

Résumé : Les aciers inoxydables à haute teneur en molybdène présentent une excellente résistance à la corrosion et ont été récemment utilisés dans des applications marines. L'acier inoxydable de type 254 SMO contient du molybdène (6% Mo) et des quantités plus élevées en éléments d'alliages que les aciers inoxydables plus classiques tels que 304, 316 et 316L. Alors que Anees Uddin Malik et al. montrent que l’acier 254 SMO est moins sensible à la corrosion par piqûre en eau de mer du golfe persique, Abdulsalam et al. démontrent que bien que cet acier présente une bonne résistance à la corrosion, il reste encore sensible à une corrosion caverneuse (surtout en milieu à 16% en masse d’ion chlorure ou à plus de 30°C).La première partie de ce travail traite du comportement électrochimique de l’acier inoxydable 254 SMO immergé dans l’eau de mer naturelle en laboratoire. Ainsi deux sites de la Guyane ont été choisis pour effectuer des prélèvements d’eau. Des analyses physicochimiques de ces eaux sont réalisées et montrent que l’eau du site du Port Larivot contient une quantité en ions chlorures plus importante que celle de l’eau du site du Mahury. Une colonisation par des bactéries et crustacés (balanes) a été mise en évidence, à l’aide du microscope électronique à balayage environnemental. Les mesures électrochimiques, notamment la voltammétrie cyclique a montré l’existence d’une zone de passivation et l’augmentation du courant de passivation par un facteur de 10 en présence d’un biofilm pour l’acier inoxydable immergé en eau du Mahury durant 22 jours. La deuxième partie propose une étude approfondie du comportement de l’interface complexe métal/couche passive/biofilm. Trois différents coupons d’aciers inoxydables (brut, poli et grenaillé) ont été déposés sur site (in-situ) dans un premier temps. Dans une seconde étape, nous avons réalisé des expérimentations mixtes (incubation in-situ et croissance en laboratoire). L’évolution du potentiel d’abandon de ces aciers est très proche pour l’acier brut et l’acier poli. En revanche, celui de l’acier grenaillé, de par la présence des grains d’alumine à sa surface, affiche un comportement différent. Une étude comparative des deux expérimentations montre des différences concernant les paramètres électriques de l’interface complexe métal/couche passive/biofilm.
Stainless steels with high content in molybdenum present an excellent corrosion resistance and were recently used in marine applications. The stainless steel 254 SMO contains molybdenum (6 %) and higher amounts of alloying elements than conventional stainless steels such as 304, 316 and 316L. While Anees Uddin Malik et al. show that 254 SMO steel is less likely to be susceptible to pitting corrosion in Arabian Gulf sea water, Abdulsalam et al. demonstrate that although this steel has good resistance to corrosion, it remains still susceptible to crevice corrosion (especially in environment with 16 chloride percent weight or more than 30 ° C).The first part of this work deals with the electrochemical behaviour of stainless steel 254 SMO immersed in natural seawater at laboratory. Two sites in French Guyane were chosen to take samples of seawater. Physicochemical analyses of these waters are made and show than the in Port Larivot site seawater contains a higher quantity of chloride ion than to Mahury seawater. Colonization by bacteria and crustaceans (barnacles) was highlighted, using the environmental scanning electron microscope. The electrochemical measurements, including cyclic voltammetry showed the existence of a passivation region and increasing the passivation current by a factor of 10 in the presence of biofilm on stainless steel immersed in Mahury seawater during 22 days.The second part offers a detailed study of the behaviour of the interface metal/passive film/biofilm. Three different coupons of stainless steel (crude, polished and blasted) were deposited on the site (in-situ) in the first time. In a second step, we performed experiments mixed (in-situ incubation and growth in the laboratory). The evolution of the free potential of these steels is very close for crude steel and polished steel. Conversely, the blasted steel, by the presence of alumina grains on its surface, shows a different behaviour. A comparative study of those two experiments shows differences in the electrical parameters of the interface metal/passive film/biofilm.

http://www.theses.fr/2013AGUY0598/document

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A suite of eclogite xenoliths from the Roberts Victor kimberlite (South Africa) is remarkable for its high abundances of base metal sulfides (BMS; up to 2 modal %). However, while sulfides are nearly ubiquitous in Type I eclogites (garnet > 0.07% Na2O), Type II eclogites (garnet < 0.07% Na2O) systematically lack sulfides. Two different sulfide assemblages are recognised within the Type I xenolith suite. Both populations are polyphase Cu-Ni-Fe sulfides, one characterised by the pyrrhotite (Po) + pentlandite (Pn) + chalcopyrite (Cp) assemblage and the other by the smythite/violarite (Smy/Vi) + (Ni)pyrite (Py) + Cp assemblage. The latter is the most abundant assemblage and reflects the supergene alteration of the "primary" Po + Pn + Cp assemblage. This process overprints the original composition of the sulfides by remobilising elements such as S, Fe, Ni, Se and Te. In the Type I eclogites, BMS occur as inclusions within silicates (garnet and clinopyroxene) and as interstitial grains. No chemical differences were observed between enclosed and interstitial sulfides. However, their relative abundances are correlated, indicating a similar origin. The Po + Pn + Cp assemblage is identical to eclogitic sulfides previously described in some Roberts Victor diamonds. Silicate-enclosed sulfides could appear to be early phases, but they are restricted to the outer parts of the silicate grains, suggesting a late incorporation during partial recrystallisation of silicate phases, induced by fluid-rock percolation-reaction during a metasomatic event. Positive whole-rock correlations between Se and (La/Sm)N⁎ and between Cu and ΣLREEN⁎ indicate a direct link between sulfide content and the enrichment of Mg + incompatible elements in the Type I eclogites, further supporting a metasomatic origin of the sulfide component. Similarly, a negative correlation between ΣLREEN⁎ and Cucpx implies that the metasomatic agent was at least partially composed of S-rich fluid (e.g. H2S, SO2) that reacted with the rock and leached Cu out of the silicates. The coupling between sulfides and LREE in the Type I eclogites, as well as the absence of sulfides and metasomatic features (e.g. unequilibrated grain boundaries, melt pockets, fluid inclusions, phlogopite) in the Type II eclogites, demonstrate that Type II eclogites did not undergo such a metasomatic event and therefore may represent the less-modified protoliths of Type I eclogites.
ISSN: 0009-2541

hal-00903856
https://hal.archives-ouvertes.fr/hal-00903856
DOI : 10.1016/j.chemgeo.2013.06.015

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The platinum-group element (PGE) systematics of continental mantle peridotites show large variability, reflecting petrogenetic processing of the upper mantle during partial melting and melt/fluid percolation inside the lithosphere. By removing Pd-Cu-Ni rich sulfides, partial melting events that have stabilized the sub-continental mantle lithosphere fractionated PPGEs (Palladium-group PGE; Pt, Pd) relative to IPGEs (Iridium-group PGE; Os, Ir, Ru, Rh). Residual base-metal sulfides (BMS) survive as enclosed IPGE-enriched Monosulfide Solid Solutions (Mss), which otherwise decompose into Ru-Os-Ir-rich refractory platinum-group minerals (PGMs) once the partial melts become S-undersaturated. The small-scale heterogeneous distribution of these microphases may cause extreme nugget effects, as seen in the huge variations in absolute PGE concentrations documented in cratonic peridotites. Magmas fluxing through the lithospheric mantle may change the initial PGE budgets inherited from the melting events, resulting in the great diversity of PGE systematics seen in peridotites from the sub-continental lithosphere. For instance, melt-rock reactions at increasing melt/rock ratios operate as open-system melting processes removing residual BMS/PGMs. Highly percolated peridotites are characterized by extreme PGE depletion, coupled with PGE patterns and Os-isotope compositions that gradually evolve toward that of the percolating melt. Reactions at decreasing melt-rock ratios (usually referred to as "mantle metasomatism") precipitate PPGE-enriched BMS that yield suprachondritic Pd/Ir and occasionally affect Pt/Ir and Rh/Ir ratios as well. Moreover, volatile-rich, small volume melts fractionate Os relative to Ir and S relative to Se, thereby producing rocks with supra-chondritic Os/Ir and S/Se coupled with supra-chondritic Pd/Ir and Pt/Ir. Major magmatic inputs at the lithosphere-asthenosphere boundary may rejuvenate the PGE systematics of the depleted mantle. Integrated studies of "refertilized" peridotites with worldwide provenance provide evidence for mixing between old PGM-rich harzburgitic protoliths and newly-precipitated BMS. Long-lived PGMs carry the Os-isotope compositions of ancient melt‐depletion events into seemingly undepleted fertile lherzolites. Another diagnostic feature of major refertilization processes is the increasing modal abundance of Pt-Pd-Te-Bi or Pt-As-S microphases. Due to regional-scale refertilization processes, sizeable (> 100 km) domains of the upper lithospheric mantle are now significantly enriched in Pd, Au, Cu, Se, and other incompatible chalcophile elements that are of considerable importance in PGE-ore forming events.
ISSN: 0024-4937

hal-00828626
https://hal.archives-ouvertes.fr/hal-00828626
DOI : 10.1016/j.lithos.2012.08.017

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Homogenization models are widely used to predict the evolution of texture (crystal preferred orientations) and resulting anisotropy of physical properties in metals, rocks, and ice. They fail, however, in predicting two main features of texture evolution in simple shear (the dominant deformation regime on Earth) for highly anisotropic crystals, like olivine: (1) the fast rotation of the CPO towards a stable position characterized by parallelism of the dominant slip system and the macroscopic shear and (2) the asymptotical evolution towards a constant intensity. To better predict CPO-induced anisotropy in the mantle, but limiting computational costs and use of poorly-constrained physical parameters, we modified a viscoplastic self-consistent code to simulate the effects of subgrain rotation recrystallization. To each crystal is associated a finite number of fragments (possible subgrains). Formation of a subgrain corresponds to introduction of a disorientation (relative to the parent) and resetting of the fragment strain and internal energy. The probability of formation of a subgrain is controlled by comparison between the local internal energy and the average value in the polycrystal. A two-level mechanical interaction scheme is applied for simulating the intracrystalline strain heterogeneity allowed by the formation of low-angle grain boundaries. Within a crystal, interactions between subgrains follow a constant stress scheme. The interactions between grains are simulated by a tangent viscoplastic self-consistent approach. This two-level approach better reproduces the evolution of olivine CPO in simple shear in experiments and nature. It also predicts a marked weakening at low shear strains, consistently with experimental data.
ISSN: 0012-821X

hal-01243503
https://hal.archives-ouvertes.fr/hal-01243503
DOI : 10.1016/j.epsl.2015.08.018

Éditeur(s) : Elsevier
Résumé : The distribution and speciation of mercury (Hg) in the water column, the inputs (wet deposition and tributaries) and the outputs (atmospheric evasion and outlet) of an artificial partially anoxic tropical lake (Petit-Sa-Lit reservoir, French Guiana) were investigated oil a seasonal basis in order to appraise the cycling and transformations of this metal. The total mercury (HgT) concentrations in the oxygenated epilimnetic waters averaged 5 +/- 3 pmol L-1 in the unfiltered samples (HgTUNF) and 4 +/- 2 pmol L-1 in the dissolved (HgTD) phase (< 0.45 mu m). On average, the monomethylmercury (MMHg) constituted 8%, 40%, and 18% of the HgT in the dissolved phase, tile particulate suspended matter and in tile unfiltered samples, respectively. Covariant elevated concentrations of particulate MMHg and chlorophyll a in the epilimnion suggest that phytoplankton is ail active component for the MMHg transfer in tile lake. In the anoxic hypolimnion the HgTUNF averages 13 +/- 6 pmol L-1 and tile HgTD 8 +/- 4 pmol L-1. The averages of MMHgP and MMHgD in hypolimnetic waters were two and three times the corresponding values of the epilimnion, 170 +/- 90 pmol g(-1) and 0.9 +/- 0.5 pmol L-1, respectively. In the long dry and wet seasons, at the flooded forest and upstream dam sampling stations, the vertical profiles of MMHgD concentrations accounted for two distinct maxima: one just below the oxycline and the other near the benthic interface. Direct wet atmospheric deposition accounted for 14 moles yr(-1) HgTUNF, with 0.7 moles yr(-1) as MMHgUNF, while circa 76 moles yr(-1) of HgTUNF, with 4.7 moles yr(-1) as MMHgUNF, coming from tributaries. Circa 78 moles (similar to 17% as MMHg) are annually exported through tile dam, while 23 moles yr(-1) of Hg-0 evolve in the atmosphere. A mass balance calculation suggests that the endogenic production of MMHgUNF attained 8.1 moles yr(-1), corresponding to a methylation rate of 0.06% d(-1). As a result, tile Petit-Saut reservoir is a large man-made reactor that has extensively altered mercury speciation in favor of methylated species.
Applied Geochemistry (0883-2927) (Elsevier), 2008-05 , Vol. 23 , N. 5 , P. 1101-1126

Droits : 2008 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/2008/publication-4198.pdf
DOI:10.1016/j.apgeochem.2007.11.006
http://archimer.ifremer.fr/doc/00000/4198/

Éditeur(s) : HAL CCSD
Résumé : International audience
This study was designed to identify in the pearl oyster Pinctada margaritifera, used as a bio-accumulator, molecular biomarkers for the presence of heavy metals in the lagoon environment. Pearl oysters were exposed to 2 concentrations (1 and 10 μg L− 1) of cadmium (Cd) and chromium (Cr) compared to a control. Twelve target genes encoding proteins potentially involved in the response to heavy metal contamination with antioxidant, detoxification or apoptosis activities were selected. P. margaritifera accumulated Cd but not Cr, and mortality was related to the amount of Cd accumulated in tissues. In response to Cd-Cr contamination, metallothionein (MT) was significantly up-regulated by Cd-Cr at both concentrations, while 7 others (SOD, CAT, GPX, GSTO, GSTM, CASP, MDR) were down-regulated. Based on the development of these molecular tools, we propose that the pearl oyster, P. margaritifera, could be used as a sentinel species for heavy metal contamination in the lagoons of tropical ecosystems.
. Marine Pollution Bulletin

hal-01526382
https://hal.archives-ouvertes.fr/hal-01526382
DOI : 10.1016/j.marpolbul.2017.03.012
PUBMED : 28320509

Éditeur(s) : HAL CCSD Elsevier
Résumé : Understanding chemical element mobility during high-pressure metamorphism is paramount to the knowledge of the transformations occurring during the course of eclogite-facies metamorphism. In particular, the role of deformation and fluid circulation appear essential. In order to better decipher this role, we investigated two eclogite-facies samples from the Lindas Nappe in the Bergen arcs (Norwegian Caledonides), which are related to a fluid/deformation metamorphic event. This study, based on detailed microtextural investigations, coupled with major and trace element analyses, either in situ EMPA and LA-ICP-MS or by conventional ICP-MS nebulisation on mineral fractions, illustrates the complexity of chemical reactions accompanying the eclogite- and amphibolite-facies metamorphism. A single eclogite-facies mineral species two eclogite-facies (i.e. phengite and epidote) depicts various chemical features depending on its textural location at thin-section scale. The correlation with the mineralogical reaction occurring in each textural site demonstrates that the compositional variations are inherited from the precursor minerals. Thus, the composition of eclogite-facies minerals is locally controlled by the composition of few hundred-micron domains. On the contrary, alteration phases of the amphibolite facies (symplectite and calcic amphibole) display clear enrichment in LILE, Pb, Sr and LREE compared to their precursor minerals (omphacite and garnet). This supports that the transport of elements at hand-sample scale was enhanced during the retrogression and elements were efficiently delocalised from one textural site to another. The contrasting behaviour of element mobility between peak eclogite-facies metamorphism and retrogression can be explained in terms of rate processes and fluid/deformation activity. During eclogitisation,deformation allows the formation of textural and mineralogical microdomains. Contemporaneously the fluid circulation favours the development of heterogeneities by transport of elements in excess towards areas protected from deformation where phengite-bearing quartz lenses crystallise. This, together with the very fast recrystallisation of eclogite-facies minerals, results in a heterogeneous redistribution of elements at sample scale and in a chemical disequilibrium between different microdomains of hundred-micron size. During retrogression in the amphibolite facies, coeval with long-term ductile deformation, the fluids act as an efficient vector to redistribute the elements from a given textural site to another and, thus, allow to reach, at hand-sample scale, a new chemical equilibrium between the different crystallising phases.
ISSN: 0024-4937

hal-00404602
https://hal.archives-ouvertes.fr/hal-00404602
DOI : 10.1016/j.lithos.2006.10.001

Éditeur(s) : HAL CCSD Society of Economic Geologists
Résumé : International audience
The ~8-Moz Sadiola Hill gold deposit is located in the Kédougou-Kénieba inlier, a window of deformed ca. 2200 to 2050 Ma rocks that crop out in eastern Senegal and western Mali. The geology of the inlier differs from other Paleoproterozoic granite-greenstone belts and sedimentary basins by the abundance of carbonate rocks. The Sadiola Hill gold deposit occurs within 3 km of the Senegal-Mali shear zone, and country rocks in the region have undergone polycyclic deformation. The lithostratigraphy of the open pit consists of impure limestones overlain by younger sequences of detrital sedimentary rocks, which include arenite, wacke, and siltstone. The sedimentary rocks have been subjected to regional greenschist-facies metamorphism and have been intruded by multiple generations of synkinematic, calc-alkaline stocks and dikes. The bulk of the ore is hosted within a N-S- to NNW-trending, 10- to 50-m-wide, brittle-ductile dilational shear zone defined as the Sadiola shear zone. Gold lodes also occur along an array of steep NNE-trending shear zones. Geometric and kinematic analyses indicate that the ore-hosting structures were undergoing sinistral displacement at the time of mineralization, locally defined as the D3s NNW-SSE-shortening event. Hydrothermal alteration is polyphase and includes an early high-temperature calc-silicate phase (i.e., porphyroblastic growth of actinolite-tremolite) followed by a potassic phase (i.e., biotite-calcite-quartz ± K-feldspar-tourmaline-actinolite) that was synchronous with ore mineral deposition. Paragenetic studies reveal a multistage ore development that includes an As-rich sulfide stage, followed by an Au-Sb stage. The ore is associated with a metal enrichment suite of Au-As-Sb ± Cu-Fe-W-Mo-Ag-Bi-Zn-Pb-Te. The Sadiola Hill deposit shares a similar relative timing and structural setting to that of other world-class orogenic gold systems in the West African craton (e.g., Ashanti, Loulo), with gold deposition occurring during a period of transcurrent tectonics, after the cessation of region-wide compressional deformation. The high-temperature paragenesis at Sadiola Hill is atypical of gold mineralization in the craton and indicates that the late Eburnean tectono-magmatic activity between ca. 2080 and 2060 Ma played an important role in the dynamics of hydrothermal fluid circulation along the Senegal-Mali shear zone.
ISSN: 0361-0128

hal-01583358
https://hal.archives-ouvertes.fr/hal-01583358
DOI : 10.2113/econgeo.112.1.23

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Trivalent inorganic arsenic [As(III)] is an efficient anticancer agent used to treat patients suffering from acute promyelocytic leukemia. Recently, experimental studies have clearly demonstrated that this metalloid can also cure lymphoproliferative and/or pro-inflammatory syndromes in different murine models of chronic immune-mediated diseases. T helper (Th) 1 and Th17 lymphocytes play a central role in development of these diseases, in mice and humans, especially by secreting the potent pro-inflammatory cytokine interferon-γ and IL-17A, respectively. As(III) impairs basic functions of human T cells but its ability to modulate secretion of pro-inflammatory cytokines by differentiated Th lymphocytes is unknown. In the present study, we demonstrate that As(III), used at concentrations clinically achievable in plasma of patients, has no effect on the secretion of interferon-γ from Th1 cells but almost totally blocks the expression and the release of IL-17A from human Th17 lymphocytes co-stimulated for five days with anti-CD3 and anti-CD28 antibodies, in the presence of differentiating cytokines. In addition, As(III) specifically reduces mRNA levels of the retinoic-related orphan receptor (ROR)C gene which encodes RORγt, a key transcription factor controlling optimal IL-17 expression in fully differentiated Th17 cells. The metalloid also blocks initial expression of IL-17 gene induced by the co-stimulation, probably in part by impairing activation of the JNK/c-Jun pathway. In conclusion, our results demonstrate that As(III) represses expression of the major pro-inflammatory cytokine IL-17A produced by human Th17 lymphocytes, thus strengthening the idea that As(III) may be useful to treat inflammatory immune-mediated diseases in humans.
ISSN: 0041-008X

inserm-00872871
http://www.hal.inserm.fr/inserm-00872871
DOI : 10.1016/j.taap.2012.05.004
PUBMED : 22617429

Éditeur(s) : HAL CCSD Elsevier
Résumé : Two peat sequences were sampled in the vicinity of the main mining districts of the Vosges Mountains: Sainte-Marie-aux-Mines and Plancher-les-Mines. Lead isotopic compositions and excess lead fluxes were calculated for each of these radiocarbon-dated sequences. Geochemical records are in very good agreement with the mining history of the area, well known over the last millennium. Except for an anomaly corresponding to the Middle Bronze Age which has not yet been resolved, there is no clear geochemical evidence of local metal production in the Vosges before the 10th century as excess lead deposition archived between 500 BC and 500 AD is attributed to long-range transport of polluted particulate matter. The approach described here can be applied to other mining districts where archaeological evidence is scarce or even lacking, but where past exploitation is suspected.
ISSN: 0375-6742

hal-00512409
https://hal.archives-ouvertes.fr/hal-00512409
DOI : 10.1016/j.gexplo.2010.05.004

Éditeur(s) : Springer Berlin / Heidelberg
Résumé : The role of particles in the fate and speciation of trace metals in macrotidal estuaries was studied using a surface complexation model (MOCO). Cadmium was selected as the target metal contaminant due to its reactivity in estuaries: cadmium behavior is mainly controlled by heterogeneous processes (sorption/desorption) related to salinity and suspended matter gradients. Various scenarios of suspended matter distribution according to salinity were simulated. The impact of surface properties (specific surface area, density of surface sites, acido-basic properties, and complexation constant) was evaluated using data collected on particles from the Gironde, Loire, and Seine estuaries. Our results show that particle surface properties, evaluated on the basis of various parameters, are instrumental in "non-conservative" contaminant speciation in the estuarine environment. Their evaluation enables us to understand and simulate, to a large extent, the fate of "Cd-type" contaminants (whose behavior is controlled by competition between sorption and desorption processes). The natural variations of these properties can be responsible for significant modifications of the Cd speciation in the macrotidal estuaries where salinity and SM gradients are very strong.
The Handbook of Environmental Chemistry (1433-6839) (Springer Berlin / Heidelberg), 2006 , Vol. 5H , P. 265-301

Droits : 2006 Springer
http://archimer.ifremer.fr/doc/2006/publication-2005.pdf
DOI:10.1007/b89479
http://archimer.ifremer.fr/doc/00000/2005/

Éditeur(s) : HAL CCSD Taylor & Francis: STM Behavioural Science and Public Health Titles Taylor & Francis: STM, Behavioural Science and Public Health Titles
Résumé : We have investigated by electron tomography, in a transmission electronic microscope, the interactions between dislocations in olivine single crystals and polycrystals deformed in axial compression at T < 1000 °C (T < 0.5Tm). Dislocations are mostly of the [0 0 1] type, except in the polycrystal where [1 0 0] and [0 0 1] dislocations have been activated. A few 〈1 0 1〉 junctions have been found and characterized. Many collinear interactions have been identified either involving direct interactions between crossing dislocations of opposite Burgers vectors or indirect interactions between dislocations gliding in parallel planes and sessile dislocation loops. We suggest that collinear interaction, already identified as the primary source of strain hardening in FCC metals, is the main dislocation interaction mechanism in olivine deformed at temperatures below 1000 °C.
ISSN: 1478-6443

hal-01174166
https://hal.archives-ouvertes.fr/hal-01174166
DOI : 10.1080/14786435.2014.1000996

Éditeur(s) : Elsevier
Résumé : This study aimed at comparing toxic element (Hg, Cd) bioaccumulation in relation to age for bottlenose (Tursiops truncatus) and striped dolphins (Stenella coeruleoalba) from Mediterranean and Atlantic waters. Metal concentrations were also measured in selected prey to infer metal exposure through the diet. As expected, Mediterranean prey exhibited the highest Hg levels, probably as a consequence of the Hg enrichment of the Mediterranean Sea. Comparing the predators from each area and taking age into account, Mediterranean bottlenose dolphins displayed higher Hg levels than Atlantic dolphins (p = 0.032), whereas Mediterranean striped dolphins did not (p = 0.691). The consumption of Myctophid fish, which showed the highest Hg levels (105 +/- 80 ng g(-1) w.wt.) among Atlantic prey, may explain the high Hg levels in the liver of the Atlantic striped dolphins and suggested a preferential offshore feeding behaviour in this area. Concerning Cd, no clear differences were found between geographical areas. (c) 2006 Elsevier Ltd. All rights reserved.
Marine Pollution Bulletin (0025-326X) (Elsevier), 2006-10 , Vol. 52 , N. 10 , P. 1219-1230

Droits : 2006 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/2006/publication-4713.pdf
DOI:10.1016/j.marpolbul.2006.02.020
http://archimer.ifremer.fr/doc/00000/4713/