Remobilisation of uranium from contaminated freshwater sediments by bioturbation

International audiencePrevious studies have demonstrated that benthic macro-invertebrate bioturbation can influence the remobilization of uranium initially associated with freshwater sediments resulting in a high release of this pollutant through the overlying water column. Giving the potential negative effects on aquatic biocenosis and the global ecological risk, it appeared crucial to improve our current knowledge concerning the uranium biogeochemical behaviour in sediments. The present study aimed to assess the biogeochemical modifications induced by Tubifex tubifex (Annelida, Clitellata, Tubificidae) bioturbation within the sediment permitting to explain such a release of uranium. To reach this goal, uranium distribution between solid and solute phases of a reconstructed benthic system (i.e. in mesocosms) inhabited or not by T. tubifex worms was assessed in a 12 day laboratory experiment. Thanks notably to fine resolution (mm-scale) measurements (e.g. DET gels probes for porewater, bioaccumulation in worms) of uranium and main chemical species (iron, sulfate, nitrate, nitrite), this work permitted (i) to confirm that the removal of bottom sediment particles to the surface through the digestive tract of worms greatly favours the oxidative loss of uranium in the water column, and (ii) to demonstrate that both uranium contamination and bioturbation of T. tubifex substantially influence major microbial-driven biogeochemical reactions in sediments (e.g. stimulation of denitrification, sulfate-reduction and iron dissolutive reduction). This study provides the first demonstration of biogeochemical modifications induced by bioturbation in freshwater uranium-contaminated sediments

Distribution of trace elements in waters and sediments of the Seversky Donets transboundary watershed (Kharkiv region, Eastern Ukraine)

International audienceThis paper reports on the aquatic chemistry of trace elements in terms of spatial and temporal distribution, but also pollution sources in the transboundary watershed of the Seversky Donets River (Ukraine/Russia). Bed sediments and filtered water were collected from the Udy and Lopan Rivers at sites from the river source in the Belgorod region (Russia) to rural and urban areas in the Kharkiv region (Ukraine) in May and August 2009. Priority trace elements (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn), an urban tracer (Ag) and additional metals (Co, Mo, V) and Th were measured in stream water and sediments. The low levels and variability of Th-normalized concentrations indicated the absence of geochemical anomalies in the upstream part of the rivers and suggested that these data represent a regional baseline for trace elements in bed sediments. In contrast, water and sediments within the city of Kharkiv were contaminated by Ag, Pb, Cd, Cu, Cr and Zn, which are mainly attributed to municipal wastewater inputs and urban run-off. Results of the environmental quality assessment showed that element concentrations in the sediments can be considered as potentially toxic to aquatic organisms in sites downstream of the wastewater discharges

Morphology and variability of the facial nerve trunk dependent on branching pattern, gender, anthropometric type and side of the head in Moldovan population

Background: Knowledge concerning variability of the facial nerve trunk (FNT) direction after its exit through the stylomastoid foramen is of a great clinical significance for maxillofacial surgeons, otorhinolaryngologists, oncologists, specialists in plastic and aesthetic surgery. The aim of our study was to establish the variation of the FNT direction and its peculiarities dependent on branching pattern, gender, anthropometric type and side of the head. Materials and methods: The direction of the FNT and its branching pattern were studied on 75 dissected hemifaces of adult formalized cadavers (59 male/16 female), and the morphometry of the FNT length, width and bifurcation angle was carried out. Results: Seven branching patterns of the facial nerve were established: Type I – 18.7%, Type II – 14.7%, Type III – 20%, Type IV – 14.6%, Type V – 5.3%, Type VI – 18.7%, and Type-NI – 8% (bizarre types). The FNT had a descending direction in 73.3% of cases; ascending FNT – 9.3% (including 5.3% of very short diffuse branching trunks and 1.3% of arch-shaped FNT); horizontal FNT – 10.7%; number variants – 6.7%. The male/female ratio of the descending FNT was 69.5%/87.4%; ascending – 10.2%/6.3%; horizontal – 11.9%/6.3%; number variants – 8.4% (only in male). The right/left ratio of the descending FNT was 62.9%/82.5%; ascending – 11.4%/7.5%; horizontal – 11.4%/10%; number variants – 14.3% (only on the right side). The ratio of the descending FNT in mesocephalic type (MCT) / brachycephalic type (BCT) / dolichocephalic type (DCT) was respectively 70.6%/100%/66.7%; ascending – 12.1%/0%/0%; horizontal – 12.1/0%/11.1%. Numerical variants in MCT – 5.2%, in DCT – 22.2%. The mean number of FNT in MCT/BCT/DCT was respectively 1.07/1.0/1.22. Conclusions: Three main directions are characteristic for FNT: the descending, ascending and horizontal ones, which vary dependent on branching pattern, gender, shape and side of the head

Determination of palladium, platinum and rhodium concentrations in urban road sediments by laser ablation-ICP-MS.

The introduction of catalytic converter technology to cars has alleviated gaseous exhaust emissions but in turn has resulted in emissions of the three platinum group metals (PGMs), Pd, Pt and Rh, contained in the automobile catalyst. The environmental effects of PGMs are still largely unknown and their accurate determination is particularly difficult because concentrations are at trace levels. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a direct trace element measurement technique and can be used for the rapid characterization of metals in solid environmental matrices. Here, the capability of LA-ICP-MS for the direct quantitative determination of PGMs in road sediments was assessed. Two Nd:YAG laser systems operating at 266 and 1064 nm, respectively, were coupled to an ICP-MS. Uncontaminated road sediments were spiked with PGMs, both as solution and as solid certified reference material, and used to assess the analytical performance of the technique and to calibrate the instrument. Interferences due to the formation of molecular ions and double charged ions were investigated. The LA-ICP-MS was then used to determine the concentration of PGMs in a recent urban road sediment and the results were compared with high resolution-ICP-MS measurements after microwave sample digestion with Aqua Regia. The LA-ICP-MS allows the quantitative analysis of Pd, Pt, and Rh in road sediments at sub microgram per gram levels with a relative standard deviation of 10% and with estimated detection limits in the lower nanogram per gram range. Good agreement between LA-ICP-MS and HR-ICP-MS analysis could be obtained for Pt and Rh (<3% R.S.D. at ca. 100 ng g−1) whereas the determination of Pd remains subject to interferences

Hydroxyapatite With Environmental Applications

International audienceThe aim of this study was to synthetize new nanoparticles based on methyltrimethoxysilane coatedhydroxyapatite (MTHAp) for lead removal in aqueous solutions. The morphological and compositional analysis ofMTHAp was investigated by scanning electron microscopy (SEM) equipped with an energy dispersive X-rayspectrometer (EDS). Removal experiments of Pb2+ ions were carried out in aqueous solutions with controlledconcentration of Pb2+ and at fixed pH of 5. After the removal experiment of Pb2+ ions from solutions, poroushydroxyapatite nanoparticles were transformed into PbMTHAp_5 via the adsorption of Pb2+ ions followed by a cationexchange reaction. Our results demonstrate that the porous hydroxyapatite nanoparticles can be used as an adsorbent forremoving Pb2+ ions from aqueous solution

Simultaneous release of sulphide with Fe, Mn, Ni and Zn in marine harbour sediment measured using a combined metal/sulphide DGT probe.

The technique of DGT (Diffusive Gradients in Thin Films) was further developed to allow simultaneous measurement of sulfide and trace metals at the same location in sediment. The new combined DGT probe consisted of a layer of gel impregnated with AgI, overlain by (1) a layer of gel containing Chelex, (2) a layer of gel and (3) a filter membrane. Diffusion of sulfide was controlled by layers (1) to (3), while diffusion of metals was controlled by layers (2) and (3). The Chelex gel trapped metals that were measured after elution with acid. The AgI gel trapped sulfide through the formation of Ag2S. This was then measured densitometrically as the colour changed from pale yellow to grey. Experiments demonstrated that concentrations of metal or sulfide measured by the combined device were no different to the concentrations measured by more conventional devices. The presence of Chelex in the gel did not impede the diffusion of sulfide. Deployment of a combined probe in marine sediment revealed simultaneous remobilisation of metals and sulfide at the same location. Solubility calculations indicated that some precipitation of amorphous FeS was probably occurring at the maxima in sulfide concentrations. There was general undersaturation with respect to NiS, but ZnS was supersaturated at all locations. There appeared to be localised active zones of organic matter decomposition, where reduction of manganese oxides, iron oxides and sulfate occurred simultaneously. Mass balance calculations indicated that Ni could not be supplied by release from decomposing organic matter. Manganese oxides were the most likely source, but supply from reductive dissolution of iron oxides could not be entirely discounted. Supply from either Fe or Mn oxides could account for the Zn maxima. Application of the newly developed combined probe provides new information that helps understanding of the complex nature of trace metal and sulfur chemistry in sediments

Spatial repartition and disequilibrium of natural radionuclides from the U-Th decay chains in a small catchment in the French Pyrenees

National audienc

Crop rotation of tobacco and sunflower on Cu-contaminated land: Cu phytoextraction, ecological restoration of ecosystem services, and biomass production for conversion technologies in line with the Bio-Economy

International audienc