Chlor-alkali industrial contamination and riverine transport of mercury: Distribution and partitioning of mercury between water, suspended matter, and bottom sediment of the Thur River, France

Total dissolved and total particulate Hg mass balances were estimated during one hydrological period (July 2001–June 2002) in the Thur River basin, which is heavily polluted by chlor-alkali industrial activity. The seasonal variations of the Hg dynamics in the aquatic environment were assessed using total Hg concentrations in bottom sediment and suspended matter, and total and reactive dissolved Hg concentrations in the water. The impact of the chlor-alkali plant (CAP) remains the largest concern for Hg contamination of this river system. Upstream from the CAP, the Hg partitioning between dissolved and particulate phases was principally controlled by the dissolved fraction due to snow melting during spring high flow, while during low flow, Hg was primarily adsorbed onto particulates. Downstream from the CAP, the Hg partitioning is controlled by the concentration of dissolved organic and inorganic ligands and by the total suspended sediment (TSS) concentrations. Nevertheless, the particulate fluxes were five times higher than the dissolved ones. Most of the total annual flux of Hg supplied by the CAP to the river is transported to the outlet of the catchment (total Hg flux: 70 lg m2 a1). Downstream from the CAP, the bottom sediment, mainly composed of coarse sediment (>63 lm) and depleted in organic matter, has a weak capacity to trap Hg in the river channel and the stock of Hg is low (4 mg m2) showing that the residence time of Hg in this river is short

Impact of mercury atmospheric deposition on soils and streams in a mountainous catchment (Vosges, France) polluted by chlor-alkali industrial activity: The important trapping role of the organic matter

Total atmospheric Hg contamination in a French mountainous catchment upstream from a chlor-alkali industrial site was assessed using Hg concentrations in the deepest soil horizon, in the stream bottom sediments, in river waters and in bryophytes. The natural background level of Hg content deriving from rock weathering was estimated to 32 ng g1 in the deepest soil layers. The soils appear to be Hg contaminated in two stages: atmospheric deposition and leaching through the soil profiles of Hg-organic matter complexes. The Hg enrichment factor (EFHgSc) which could be calculated by normalization to a conservative element like Sc, allows to estimate the major contribution (63% to 95%) of the atmospheric inputs, even in the upper part of the basin. This contribution may be attributed to diffuse regional atmospheric deposition of Hg and is mainly due to the geographic location of the chlor-alkali plant. This study shows for the first time that the mercury enrichment is proportional to the carbon content indicating that most of the atmospheric mercury deposition is trapped by the organic matter contained in the soils and in the stream sediments. The Hg stock in the soils of the upper catchment and the soil erosion contribution to the riverine Hg fluxes are estimated for the first time and allow to assess the Hg residence time. It indicates that Hg is trapped in the soils of such a polluted catchment for probably several thousand years

Total mercury concentrations in an industrialized catchment, the Thur River basin (north-eastern France): geochemical background level and contamination factors

River bottom sediments and soils were collected from the industrialized Thur River basin (north-eastern France) to assess mercury contamination. The regional geochemical background level of total mercury was evaluated to calculate mercury contamination factors (Fc) in soils and river bottom sediments. Our estimate of the mean background mercury levels in river sediments and soils, not affected by human activities, was 232 ng g1 (range: 27–406 ng g1). Sediments contaminated by the effluent from a chlor-alkali plant yielded the highest contamination factors (Fc¼1784). Contamination factors of surficial soils within 1 km of the industrial site range from 6.3 to 43.6. This contamination is attributed to diffuse atmospheric deposition from this local plant. However, even upstream from this industrial area elevated contamination factors were recorded for river bottom sediments (Fc¼3.2 to 26.4) and for one alluvial soil profile (Fc¼10). This is possibly due to past pollution resulting from waste water discharges. Mercury contamination in the different horizons of alluvial soils is not correlated with soil organic carbon content, but may be the result of occasional accidental pollution arising from the introduction of contaminated suspended particulate matter by the Thur River during periods of flooding

Identifying the origins of local atmospheric deposition in the steel industry basin of Luxembourg using the chemical and isotopic composition of the lichen Xanthoria parietina

Trace metal atmospheric contamination was assessed in one of the oldest European industrial sites of steel production situated in the southern part of the Grand-Duchy of Luxembourg. Using elemental ratios as well as Pb, Sr, and Nd isotopic compositions as tracers, we found preliminary results concerning the trace metal enrichment and the chemical/isotopic signatures of the most important emission sources using the lichen Xanthoria parietina sampled at 15 sites along a SW-NE transect. The concentrations of these elements decreased with increasing distance from the historical and actual steel-work areas. The combination of the different tracers (major elements, Rare Earth Element ratios, Pb, Sr and Nd isotopes) enabled us to distinguish between three principal sources: the historical steel production (old tailings corresponding to blast-furnace residues), the present steel production (industrial sites with arc electric furnace units) and the regional background (baseline) components. Other anthropogenic sources including a waste incinerator and major roads had only weak impacts on lichen chemistry and isotopic ratios. The correlation between the Sr and Nd isotope ratios indicated that the Sr–Nd isotope systems represented useful tools to trace atmospheric emissions of factories using scrap metal for steel production

Heavy metal distribution in the bottom sediments along Tietê river basin.

Analysis of heavy metals in fluvial sediments has been used to better understand the potential hazards and critical toxicity of heavy metals mainly related to the anthropogenic influences of urban sewage, industrial effluents and agricultural activity. The present study analyzed the heavy metals, such as Cr,Cu,Ni,Zn and Pb in the bottom sediments along the Tietê river basin, a polluted watershed in the Southeast region of brazil.The distribution of the concentrations of heavy metals in the upper basin decreased in the following order: Zn>Cr>Pb>Ni>Cu, whereas, in the middle part of the basin (wich is under strong urban and industrial influences), high concentrations of Zn, Cu and Cr were abserved measuring 648,200 and 183 µg g-1 respectively. The sequential chemical extraction in relation to the total ocncentration was used to assess the potential bioavailability of heavy metals. In the upper part of the basin, the heavy metals extracted from the bottom sediments were mainly related to the residual fraction, whereas, in the middle part of the basin, the bioavailability of Zn,Cr and Ni was higher than 60%, and these metals was mainly related to the iron oxide phase.The high concentration of heavy metals observed in the middle basin of the Tietê river(after the metropolitan area of São Paulo)when compared with the average concentration found in the geochemical bottom,showed that,in terms of enrichment factor and geoaccumulation index,the degree of pollution by Zn is high and by Ni is high to moderate in the down stream direction

Edge modification of PAHs: the effect of embedded heterocycles on the aromaticity pattern

International audienceAromaticity studies carried out on the condensed model system 2 with different heteroatoms showed that the NICS(1) aromaticity in the five-membered ring correlates with that in the parent five-membered ring having the same heteroelement. Although the local aromaticity pattern is clearly determined by the Clar structure, as evidenced by the local aromaticity values in the reference molecules R1-3, the modifying effect of the heteroatom is significant. The correlation between the NICS(1)5 and NICS(1)6 aromaticities of the neighbouring rings is excellent, by modification of the heterocycle, we can engineer the aromaticity of the connecting six-membered ring as well. Geometry based aromaticity indices do not correlate well with NICS values probably due to annellation effects between rings with different aromatic character. Calculations with the different tested basis sets don’t show significant differences, therefore the use of the computationally cheaper methods is envisaged during further investigations of corresponding systems with extended π-framework

π-Conjugated Phospholes and their Incorporation into Devices; A Component with a Great Deal of Potential

International audienceThis review serves as a brief introduction to phospholes and discusses their unique favorable properties for applications in organic electronic materials. Over the past several years, π-conjugated phospholes have been slowly making their way into devices. We report here the mode of synthesis for these π-conjugated phospholes as well as discuss the performances of the devices

Supramolecular assembly of a phosphole-based moiety into nanostructures dictated by alkynylplatinum(II) terpyridine complexes through non-covalent Pt···Pt and π–π stacking interactions: synthesis, characterization, photophysics and self-assembly behaviors

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Rare Earth Elements as Hydrological Tracers of Anthropogenic and Critical Zone Contributions: A Case Study at the Alzette River Basin Scale.

AbstractEnrichments in Gd and LREE/HREE fractionation have been observed for the dissolved and colloidal fractions in waters of the Alzette River during low flow conditions. They can be related to the effluents of the waste water treatment plants (Gd/Gd*: 8-380 and LaN/YbN: 0.02-0.07). Mean daily flux balance calculations at the basin scale show that during low flow conditions Gd only comes from the anthropogenic effluents. When flood events occur, the Gd anomaly progressively disappears and gives way to a chemical water signature, which is closer to that of natural REE sources in the basin (Gd/Gd*<1.4 and 0.11<LaN/YbN<1.5)

Phosphorus-based chromophores: Emitters for OLEDs

International audienceIn this paper, we present the development of white OLEDs (WOLEDs) using organophosphorus derivatives as fluorescent emitters. The structural changes that we have performed on and around the phosphole ring (functionalization of the phosphorus atom, nature of the substituents at the 2 and 5 position) allow the ability to tune the emission wavelengths and the color emitted by the OLEDs. Using this concept, we developed organophosphorus dopants emitting orange light, which can be mixed with a blue emitting matrix for the development of WOLEDs. The OLEDs structure allows the development of flexible OLEDs with good performance and CIE coordinates which are independent from the current density