Impact des traitement de potabilisation sur le CODB et la distribution des substances humiques et non humiques de la matière organique naturelle

Cette étude a consisté à évaluer et à comparer l'impact des traitements de coagulation-floculation, ozonation et filtration sur charbon actif en grains sur la matière organique dissoute de différentes eaux de rivières et de retenues françaises en s'appuyant sur le suivi de deux paramètres principaux, la fraction biodégradable du carbone organique dissous (CODB) et la distribution des substances humiques et non humiques (établie sur la base d'un protocole de filtration en série sur résines XAD-8 et XAD-4 ).Dans le cas des eaux étudiées, la coagulation-floculation s'est accompagnée d'une diminution importante du COD, soit 38 à 70 %, impact qui se répercute dans des proportions équivalentes au niveau de sa fraction biodégradable soit 38 à 88%. Dans la majorité des cas, la clarification conduit à l'élimination préférentielle des substances humiques (définies comme hydrophobes), qui correspondent aux fractions de plus hautes masses moléculaires. Comparativement, et pour des taux supérieurs à 1 mg O3/mg C, l'ozonation entra"ne une réduction de la fraction des substances humiques qui se traduit par une augmentation de la fraction des substances non humiques et en particulier des substances hydrophiles non adsorbées sur résines XAD-8 et XAD-4. Cette modification, d'autant plus marquée que le taux d'ozone est important, s'accompagne d'une augmentation proportionnelle de la fraction biodégradable du COD. Le suivi en usine a montré que les taux d'ozone appliqués lors d'une interozonation modifient peu la nature du COD. Par contre, la filtration sur charbon actif en aval change de manière importante la distribution de la matière organique dissoute avec une augmentation relative de la fraction hydrophobe et des composés de faibles masses moléculaires apparentes (< 1 000 daltons).The goal of our study was to evaluate the impact of water treatment processes (i.e. coagulation- flocculation, ozonation and GAC filtration) on the natural organic matter (NOM) of various river and reservoir waters based on DOC and BDOC analyses and the determination of the humic/non humic NOM distribution (fractionation of the DOC at acidic pH using two successive XAD-8 and XAD-4 resin columns). Analyses carried out on ten French raw surface waters have shown that the BDOC fraction accounted for 11 to 38 % of the DOC. The humic/non humic distribution of the NOM varied slightly with the origin of the studied water. About 50 to 60 % of the DOC was found to be incorporated into the humic fraction (NOM adsorbed on the XAD-8 resin), the hydrophilic acids (adsorbed on the XAD-4 resin) accounted for 10 to 25 % of the DOC while the non adsorbed hydrophilic solutes (hydrophilic neutrals that constitute the XAD-8/XAD-4 effluent) represented 15 to 30 % of the DOC.Clarified water samples were collected from water treatment plants after coagulation/flocculation/sand filtration when no preoxidation was used. For water utilities which included a preoxidation step in their treatment process, raw water samples were coagulated and flocculated at a laboratory scale with Jar Test equipment using the same conditions (nature of the coagulant, pH, dose) as those used in the corresponding treatment plant. Globally, 38 to 70 % of the DOC and 38 to 88 % of the BDOC were removed during coagulation-flocculation, depending on the water site. In general, the humic/non humic NOM distribution of clarified waters showed a slight increase in the proportion of the non humic organic fraction as compared to raw waters, which indicates that humic substances (higher molecular weight organics) are preferentially removed during coagulation-flocculation. Ozonation experiments were carried out on a raw water and a clarified water sampled from the same water site using a semi batch reactor (ozone was generated from high purity oxygen). For both waters, very little variation of the humic/non humic NOM distribution was observed for applied ozone doses around 0.5 mg O3/mg C or below. For higher ozone doses, the NOM distribution was dramatically changed despite only a small reduction of the DOC. The large reduction of the humic fraction was followed by a proportional increase of the non adsorbed hydrophilic solute fraction (small reduction of the DOC). As the applied ozone dose was increased from 1 to 3 mg O3/mg DOC, the non-adsorbed hydrophilic solute fraction also increased. The shift from high molecular weight organics such as humic materials to more hydrophilic organics (high polarity and low molecular weight organic solutes) during ozonation has often been mentioned in the literature. The increase of the non humic substances was followed by an increase of the BDOC. Results have also shown that higher ozone doses yield higher BDOC. Similar observations could be made with the raw and the clarified water.As a conclusion of this work, samples were collected at the different steps of a water treatment plant (raw water, clarified water, intermediate ozonated water, GAC filtered water). The impact of coagulation/flocculation, and intermediate ozonation on BDOC and the humic/non humic NOM distribution confirmed the previous observations. The GAC filtration had a large impact on the DOC distribution while the BDOC was only slightly reduced. The NOM of the treated water was found to be more hydrophobic in nature with compounds that showed apparent molecular weights below 1 000 daltons (more than 80 % of the DOC)

Breakup of the weakly bound 17F nucleus

The breakup of the radioactive 17F nucleus into a proton and 16O is studied for the reaction 17F + 208Pb --> p + 16O + 208Pb at 65 MeV/nucleon. The possibility of using this reaction as a test case for studying dynamical Coulomb reacceleration effects is assessed. It is shown that the reaction is dominated by elastic nuclear breakup (diffraction dissociation).Comment: 17 figures and 8 figure

The 1979-2005 Greenland ice sheet melt extent from passive microwave data using an improved version of the melt retrieval XPGR algorithm

Analysis of passive microwave satellite observations over the Greenland ice sheet reveals a significant increase in surface melt over the period 1979-2005. Since 1979, the total melt area was found to have increased +1.22 x 10ˆ7 kmˆ2. An improved version of the cross-polarized gradient ratio (XPGR) technique is used to identify the melt from the brightness temperatures. The improvements in the melt retrieval XPGR algorithm as well as the surface melt acceleration are discussed with results from a coupled atmosphere-snow regional climate model. From 1979 to 2005, the ablation period increases everywhere over the melt zone except in the regions where the model simulates an increased summer snowfall. Indeed, more snowfall in summer decreases the liquid water content of the snowpack, raises the albedo and therefore reduces the melt. Finally, this melt acceleration over the Greenland ice sheet is highly correlated with both Greenland and global warming suggesting a continuing surface melt increase in the future.Peer reviewe

A remote secondary binding pocket promotes heteromultivalent targeting of DC-SIGN

Dendritic cells (DC) are antigen-presenting cells coordinating the interplay of the innate and the adaptive immune response. The endocytic C-type lectin receptors DC-SIGN and Langerin display expression profiles restricted to distinct DC subtypes and have emerged as prime targets for next-generation immunotherapies and anti-infectives. Using heteromultivalent liposomes copresenting mannosides bearing aromatic aglycones with natural glycan ligands, we serendipitously discovered striking cooperativity effects for DC-SIGN+ but not for Langerin+ cell lines. Mechanistic investigations combining NMR spectroscopy with molecular docking and molecular dynamics simulations led to the identification of a secondary binding pocket for the glycomimetics. This pocket, located remotely of DC-SIGN’s carbohydrate bindings site, can be leveraged by heteromultivalent avidity enhancement. We further present preliminary evidence that the aglycone allosterically activates glycan recognition and thereby contributes to DC-SIGN-specific cell targeting. Our findings have important implications for both translational and basic glycoscience, showcasing heteromultivalent targeting of DCs to improve specificity and supporting potential allosteric regulation of DC-SIGN and CLRs in general

Evaluation of a high-resolution regional climate simulation over Greenland

A simulation of the 1991 summer has been performed over south Greenland with a coupled atmosphere–snow regional climate model (RCM) forced by the ECMWF re-analysis. The simulation is evaluated with in-situ coastal and ice-sheet atmospheric and glaciological observations. Modelled air temperature, specific humidity, wind speed and radiative fluxes are in good agreement with the available observations, although uncertainties in the radiative transfer scheme need further investigation to improve the model’s performance. In the sub-surface snow-ice model, surface albedo is calculated from the simulated snow grain shape and size, snow depth, meltwater accumulation, cloudiness and ice albedo. The use of snow metamorphism processes allows a realistic modelling of the temporal variations in the surface albedo during both melting periods and accumulation events. Concerning the surface albedo, the main finding is that an accurate albedo simulation during the melting season strongly depends on a proper initialization of the surface conditions which mainly result from winter accumulation processes. Furthermore, in a sensitivity experiment with a constant 0.8 albedo over the whole ice sheet, the average amount of melt decreased by more than 60%, which highlights the importance of a correctly simulated surface albedo. The use of this coupled atmosphere–snow RCM offers new perspectives in the study of the Greenland surface mass balance due to the represented feedback between the surface climate and the surface albedo, which is the most sensitive parameter in energy-balance-based ablation calculations.Peer reviewe

The 1958–2009 Greenland ice sheet surface melt and the mid-tropospheric atmospheric circulation

peer reviewedaudience: researcherIn order to assess the impact of the mid-tropospheric circulation over the Greenland ice sheet (GrIS) on surface melt, as simulated by the regional climate model MAR, an automatic Circulation type classification (CTC) based on 500 hPa geopotential height from reanalyses is developed. General circulation correlates significantly with the surface melt anomalies for the summers in the period 1958–2009. The record surface melt events observed during the summers of 2007–2009 are linked to the exceptional persistence of atmospheric circulations favouring warm air advection. The CTC emphasizes that summer 500 hPa circulation patterns have changed since the beginning of the 2000s; this process is partly responsible for the recent warming observed over the GrIS

‘Not a country at all’: landscape and Wuthering Heights

This article explores the issue of women’s representational genealogies through an analysis of Andrea Arnold’s 2011 Wuthering Heights. Beginning with 1970s feminist arguments for a specifically female literary tradition, it argues that running through both these early attempts to construct an alternative female literary tradition and later work in feminist philosophy, cultural geography and film history is a concern with questions of ‘alternative landscapes’: of how to represent, and how to encounter, space differently. Adopting Mary Jacobus’ notion of intertextual ‘correspondence’ between women’s texts, and taking Arnold’s film as its case study, it seeks to trace some of the intertextual movements – the reframings, deframings and spatial reorderings – that link Andrea Arnold’s film to Emily Brontë’s original novel. Focusing on two elements of her treatment of landscape – her use of ‘unframed’ landscape and her focus on visceral textural detail – it points to correspondences in other women’s writing, photography and film-making. It argues that these intensely tactile close-up sequences which puncture an apparently realist narrative constitute an insistent presence beneath, or within, the ordered framing which is our more usual mode of viewing landscape. As the novel Wuthering Heights is unmade in Arnold’s adaptation and its framings ruptured, it is through this disturbance of hierarchies of time, space and landscape that we can trace the correspondences of an alternative genealogy

Recurrent attacks of acute hepatic porphyria: major role of the chronic inflammatory response in the liver

Acute intermittent porphyria (AIP) is an inherited disorder of heme metabolism characterized by life-threatening acute neurovisceral attacks due to the induction of hepatic -aminolevulinic acid synthase 1 (ALAS1) associated with hydroxymethylbilane synthase (HMBS) deficiency. Hemin represses ALAS1 and restores metabolic equilibrium. The main issue in the medical care of AIP patients is the occurrence of debilitating recurrent attacks. Chronically ill patients require repeated hemin infusions and develop secondary hemochromatosis and have a poorer quality of life. To decipher the mechanisms underlying recurrence in AIP patients, we studied the metabolic pathways altered by chronic hemin administration. A follow-up study was conducted between 1974 and 2015 and included 602 French AIP patients, of whom 46 had recurrent AIP. Moreover, we studied the hepatic transcriptome, serum proteome, liver macrophage polarization and oxidative and inflammatory profiles of Hmbs-/- mice chronically treated by hemin and extended the investigations to 5 human explanted livers. The introduction of hemin into the pharmacopeia has coincided with a 4.4-fold increase in the prevalence of chronic patients. We show that repeated hemin infusions trigger a high level heme oxygenase 1 (HO1) response, induce a pro-oxidative iron accumulation and a complex pattern of liver inflammation with macrophage infiltration. Conclusion: chronically heme-treated AIP patients may present with symptoms of an inflammatory disease responsible for an adaptive HO1 induction that could deplete the free heme pool inducing ALAS1. Hemin remains the most effective treatment but should be restricted to patients with severe forms of AIP to prevent chronic damage