Abstract: Sensitive multi-element analysis techniques were applied to water samples collected in the vicinity of a small Zn-Pb-Cu sulfide mineralization in the region of Menez-Albot (Finistère, France). The variation of the trace-element content along a local stream shows the presence of the mineralization, mainly through a simultaneous positive anomaly in solution for a group of about 10 elements (e.g. Ni, Cu, Zn, As, Sb) which are connected with this type of mineralization. The anomaly decreases steeply due to the influx of swamp water rich in Fe, Mn and organic matter. The precipitation barrier is reflected in the stream sediment composition. Contamination from fertilizers was observed in some samples.

Abstract: This study discusses rational reproduction of liquid immiscibility in the BaO-SiO2-TiO2 system. While a ternary assessment requires sub-binary descriptions in the same thermodynamic model, the related sub-binary systems BaO-SiO2, BaO-TiO2 and SiO2-TiO2 liquid and solid phases have been evaluated using different thermodynamic models in the literature. In this study, BaO-SiO2 and SiO2-TiO2 were assessed using the Ionic Two Sublattice model (I2SL) based on experimental data from the literature. BaO-TiO2 was already assessed using this model. Binary descriptions developed were then used for the assessment of liquid immiscibility in the BaO-SiO2-TiO2 system. Ternary interaction parameters were found necessary for rational reproduction of the new ternary experimental data gathered in the present work. The model parameters for each system were evaluated using a CAPLHAD approach. A set of parameters is proposed. They show good agreement between the calculated and experimental equilibrium liquidus, liquid immiscibility and thermochemical properties in the BaO-SiO2-TiO2 system. (C) 2014 Elsevier Ltd. All rights reserved.

Abstract: This study investigated concentration profiles of trace, rare earth and platinum group metals in fluvial sediments from the Pangani river basin (43,650 km2), one of the largest river basins in Tanzania, to assess its environmental quality. Sediment samples were collected in two distinct seasons from 12 representative sites of diverse land-use practices and characterised by ICP-MS after optimised microwave digestion. Ecological risks were assessed by evaluation of pollution index and comparison with legislated sediment quality guidelines (SQG). The results revealed contamination by some trace metals (e.g. Pb, V, Cu, Cr, Ni, Cd, As, Co, Mn and Zn) in concentrations ranging from 0.7 to 2940 mg kg−1, and four rare earth elements (Y, Ce, Nd, Yb) in concentrations ranging from 0.9 (Yb) to 500 mg kg−1 dry weight (Ce), which significantly exceeded the estimated background values at some stations. Palladium was the only platinum group element that was detected in quantifiable concentrations (0.33.5 mg kg−1). Concentrations of some trace metals exceeded the SQGs at some localised areas. Principal component analysis and multivariate correlations indicated geochemical characteristics of the area as the major control of metal concentrations and spatial variability. Organic matter and clay contents also played a significant role in metal distributions. Assessment of land-use practices upstream of the sampling locations was used to trace potential anthropogenic sources of metal enrichments, where highest levels were found in areas close to urban centres and agricultural activities. The study provides baseline data for future monitoring programs, and highlights the need for more comprehensive analysis involving a wider spatio-temporal scale and ecotoxicological risk assessment.

Abstract: Laser microprobe mass analysis (LAMMA) was applied to particulate matter from the Atlantic Ocean. Inferring information about the surface layer by LAMMA was not probe X-ray microanalysis (EPXMA). Geochemically relevant groups of particles had been identified by EPXMA and cluster analysis. For both locations, the most abundant ones appeared to be those rich in silicon and the alumino-silicates. Afterwards LAMMA was applied to obtain more information about the trace element composition and surface characteristics. The iron-rich phase appeared to contain significant amounts of heavy metals and of phosphate. Lead appeared to be associated in detectable amounts with alumino-silicates in the Scheldt but not with those in the Atlantic Ocean. Inferring information about the surface layer by LAMMA was not always unambiguous.

Abstract: The 2,2′-diaminodiethylamine (DEN) functional group can be expected to have ideal properties for the chelation of transition metals and their collection from aqueous solutions, independent of the alkali and alkaline earth ions concentration. Introducing DEN into cellulose filters allows straightforward preconcentration of trace cations by a simple filtration step, and the DEN-filter constitutes a suitable target for X-ray fluorescence (XRF) analysis. The linearity between the XRF-response on the loaded DEN-filter and the trace cation concentration in the solution appears excellent, up to a total filter capacity of ca. 3 μeq.cm−2. The detection limits are around 0.5 μg. l−1 in most practical cases. Accuracy and precision are around 10%. The applicability of the proposed procedure is illustrated on a comparative basis by XRF-analysis of drinking water and surface water, after preconcentration by DEN-filtration and by alternative procedures.

Abstract: Artificially generated NaCl particles were coated with PAH's by using a condensation technique. These particles were exposed to reactive gases like ozone, bromine and nitrogen dioxide. The original as well as the exposed particles were investigated by fluorimetric analysis and by LAMMA (Laser Microprobe Mass Analysis) in the desorption mode, which allows the evaporation and characterization of surfaces of single particles. The results are interpreted in terms of possible heterogeneous atmospheric reactions. The reactivity of the considered PAH's towards nitrogen dioxide was found to be negligible. The structure of the reaction products formed with ozone was partially elucidated.

Abstract: Automated electron probe X-ray microanalysis was used to characterize some 15 000 individual suspension particles from 50 samples of suspended matter collected from different depths at 18 stations throughout the Baltic Sea and the transient area to the North Sea. For each particle, 14 minor and major elements were determined and size information data were obtained. To process this huge amount of results, multivariate analysis techniques were invoked: the particles were classified into specific types and the abundance variations of these groups were studied. It appeared that 80% of all investigated particles contained mostly silicon, and seemed to consist of quartz, and K-rich and Fe-rich aluminosilicates. The abundance of BaSO4 particles averaged 5% throughout the Baltic Sea, but amounted to up to 44% at some stations. The abundance of the Fe-rich particles varied significantly with location and depth, and averaged ∼ 4%. They were often found to be associated with significant amounts of P. Both of these particle types and the Mn-rich particles are thought to be mainly authigenic. Calcium carbonate particles are more abundant towards the North Sea (which seems to act as a source). Principal component analysis of the data revealed that most of the compositional variability can be explained by differences between deep and surface waters and by the influences of inflowing North Sea waters. Additional information about the types and sources of the suspended matter in the Baltic Sea was gained from the comparison and correlation of the single particle results with different fractions of the bulk concentrations of elements such as Al, Ca, Mn, Fe, Zn and Ba.

Abstract: Biomembranes are under constant attack of free radicals that may lead to lipid oxidation in conditions of oxidative stress. The products generated during lipid oxidation are responsible for structural and dynamical changes which may jeopardize the membrane function. For instance, the local rearrangements of oxidized lipid molecules may induce membrane rupture. In this study, we investigated the effects of mechanical stress on oxidized phospholipid bilayers (PLBs). Model bilayers were stretched until pore formation (or poration) using nonequilibrium molecular dynamics simulations. We studied single-component homogeneous membranes composed of lipid oxidation products, as well as two-component heterogeneous membranes with coexisting native and oxidized domains. In homogeneous membranes, the oxidation products with —OH and —OOH groups reduced the areal strain required for pore formation, whereas the oxidation product with ]O group behaved similarly to the native membrane. In heterogeneous membranes composed of oxidized and non-oxidized domains, we tested the hypothesis according to which poration may be facilitated at the domain interface region. However, results were inconclusive due to their large statistical variance and sensitivity to simulation setup parameters. We pointed out important technical issues that need to be considered in future simulations of mechanically-induced poration of heterogeneous membranes. This research is of interest for photodynamic therapy and plasma medicine, because ruptured and intact plasma membranes are experimentally considered hallmarks of necrotic and apoptotic cell death.