Analysis of the Major Fe Bearing Mineral Phases in Recent Lake Sediments by EXAFS Spectroscopy

Extended X-ray absorption fine structure (EXAFS) spectroscopy and chemical analyses were combined to determine the Fe bearing minerals in recent lake sediments from Baldeggersee (Switzerland). The upper section of a laminated sediment core, deposited under eutrophic conditions, was compared to the lower part from an oligotrophic period. Qualitative analysis of FeK EXAFS agreed well with chemical data: In the oligotrophic section Fe(II)-O and Fe(III)-O specieswere present, whereas a significant fraction of Fe(II)-S sulfides was strongly indicated in the eutrophic part. A statistical analysis was performed by least square fitting of normalized reference spectra. The set of reference minerals included Fe(III) oxides and Fe(II) sulfides, carbonates and phosphates. In the oligotrophic regime no satisfying fit was obtained using the set of reference spectra, indicating that siderite (FeCO3) was not present in a significant amount in these carbonate-rich sediments. Simulated EXAFS spectra for a(Cax, Fe1-x)CO3solid solution allowed reconstructing the specificfeatures of the experimental spectra, suggesting that this phase was the dominant Fe carrier in the oligotrophic section of the core. In the eutrophic part, mackinawite was positively identified and represented the dominant Fe(II) sulfide phase. This finding agreed with chemical extraction, which indicated that18-40 mol% of Fe was contained in the acid volatile iron sulfide fraction. EXAFS spectra of the eutrophic section were best fitted by considering the admixture of mackinawite and the Fe-Ca carbonate phase inferred to be predominant in the oligotrophic regim

Zinc Sorption to Three Gram-Negative Bacteria: Combined Titration, Modeling, and EXAFS Study

The acid-base and Zn sorption properties of three bacteria, Cupriavidus metallidurans CH34, Pseudomonas putida ATCC12633, and Escherichia coli K12DH5R, were investigated through an original combination of extended X-ray absorption fine structure (EXAFS) spectroscopy and equilibrium titration studies. Acid-base titration curves of the three strains were fitted with a model accounting for three conceptual reactive sites: an acidic (carboxyl and/ or phosphodiester), a neutral (phosphomonoester), and a basic (amine and/or hydroxyl) group. Calculated proton and Zn equilibrium constants and site densities compare with literature data. The nature of Zn binding sites was studied by EXAFS spectroscopy. Phosphoester, carboxyl, and unexpectedly sulfhydryl ligands were identified. Their proportions depended on Zn loading and bacterial strain and were consistent with the titration results. These findings were compared to the structure and site density of the major cell wall components. It appeared that the cumulated theoretical site density of these structures (<2 Zn nm-2) was much lower than the total site density of the investigated strains (16-56 Zn nm-2). These results suggest a dominant role of extracellular polymeric substances in Zn retention processes, although Zn binding to inner cell components cannot be excluded

Сверхлегкие генераторные модули для КВЧ-терапии

Разработаны миниатюрные генераторные модули для КВЧ-терапии, лег-ко фиксируемые в любом месте тела пациента. Могут быть использованы не только в медицине

Distribution, spéciation impact et transfert du cuivre dans un sol sous vigne (rôle de la structuration spatiale et du statut organique)

The effect of the soil organic status (SOS) on the dynamics and impact of a copper contamination was investigated in a coupled field and mesocosm study with a loamy vineyard soil that had been amended with conifer compost (CC) or not amended (NA) during a previous long-term field experiment. Soil mesocosms were contaminated at 240 mg Cu kg-1 and incubated for 24 months. Cu distribution and dynamics were assessed in the solid matrix at the microscale by size fractionation of soils and in the soil solution by measuring total and free exchangeable copper concentrations (Cu2+). Copper bioavailability, CuBio, was also measured with a whole-cell biosensor. The impact of copper on soil bacterial community was evaluated through the monitoring of the amount of copper-resistant bacteria and through the variations in bacterial community structure using ARISA (Automated-Ribosomal-Intergenic-Spacer-Analysis). Results showed that copper distribution, speciation and bioavailability are strongly different in the NA and CC soils, demonstrating that the organic status of soils largely controls the solid and liquid speciation of copper as well as its availability to microorganisms. Cu was shown to be dominantly distributed in the smallest size fractions (250 m) of the CC soil. The coarser and finest size fractions of the soil are also the ones that release more Cu2+ and CuBio, explaining thus the important amount of Cu-resistant bacteria inhabiting these fractions and the differentiated temporal impact on the structure of soil bacterial community. The distribution of cultivable bacteria varied strongly between the two soils and was found to be well correlated with the distribution of added OM that controls thus bacterial community structure. The preferential impacts of copper observed in the smallest size fractions of the non amended soil demonstrate that copper toxicity and impact is also controlled by the reactivity of the soil fractions. This reactivity controls especially the release and the liquid speciation of Cu and thus bacteria-metal contact. A clear relationship between copper speciation, bioavailability, distribution and impact was established in the present study and will permit better predicting the fate and impact of metals in soils, by accounting for microscale control of metal impactThe effect of the soil organic status (SOS) on the dynamics and impact of a copper contamination was investigated in a coupled field and mesocosm study with a loamy vineyard soil that had been amended with conifer compost (CC) or not amended (NA) during a previous long-term field experiment. Soil mesocosms were contaminated at 240 mg Cu kg-1 and incubated for 24 months. Cu distribution and dynamics were assessed in the solid matrix at the microscale by size fractionation of soils and in the soil solution by measuring total and free exchangeable copper concentrations (Cu2+). Copper bioavailability, CuBio, was also measured with a whole-cell biosensor. The impact of copper on soil bacterial community was evaluated through the monitoring of the amount of copper-resistant bacteria and through the variations in bacterial community structure using ARISA (Automated-Ribosomal-Intergenic-Spacer-Analysis). Results showed that copper distribution, speciation and bioavailability are strongly different in the NA and CC soils, demonstrating that the organic status of soils largely controls the solid and liquid speciation of copper as well as its availability to microorganisms. Cu was shown to be dominantly distributed in the smallest size fractions (250 m) of the CC soil. The coarser and finest size fractions of the soil are also the ones that release more Cu2+ and CuBio, explaining thus the important amount of Cu-resistant bacteria inhabiting these fractions and the differentiated temporal impact on the structure of soil bacterial community. The distribution of cultivable bacteria varied strongly between the two soils and was found to be well correlated with the distribution of added OM that controls thus bacterial community structure. The preferential impacts of copper observed in the smallest size fractions of the non amended soil demonstrate that copper toxicity and impact is also controlled by the reactivity of the soil fractions. This reactivity controls especially the release and the liquid speciation of Cu and thus bacteria-metal contact. A clear relationship between copper speciation, bioavailability, distribution and impact was established in the present study and will permit better predicting the fate and impact of metals in soils, by accounting for microscale control of metal impactSAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Analysis and dating of Pb, Cd, Cu, Zn sediment profiles from the Vitznau basin of Lake Lucerne (Switzerland) / Analyse et datation de profils en Pb, Cd, Cu, Zn de sédiments lacustres provenant du lac des Quatre Cantons, Suisse (bassin de Vitznau)

Abstract: Two parallel sediment cores were recovered in the Vitznau basin of Lake Lucerne, Switzerland, were analysed for % dry weight and for Pb, Cd, Cu, Zn. The dry weight and the four metal profiles show two anomalies at 12 cm and at 39 cm core depth pointing to anomalous sedimentation events. The first anomaly (at 1 2 cm) can be related to the rock fall of the Biirgenstock at Obermatt which occurred in two phases in 1963 and 1964. The second anomaly (at 39 cm) is related to the slide of the Vitznau river in 1674. The mean sedimentation rates, obtained from these two events and the dry weight profiles are S1997.1964 = 0.041 g cm-2 y1 and S,962 .674 = °-025 g cm"2 Г1- The difference in the rates is supposedly primarily due to the deposition of organic matter related to eutro- phication which started in 1954. Before 1800 the metal profiles are constant and these concentrations are considered to represent pre-industrial geochemical background concentrations: 37.9 ±1.8 mg/kg for Pb, 0.53 ±0.10 mg/kg for Cd, 33.0 ± 2.6 mg/kg for Cu, and 103.9 ±5.5 mg/kg for Zn. From 1800 up to 1950 all four metal concentrations increase exponentially and decrease from 1970 onwards to recent days. We consider these curves as related to the increasing diffusive emission of heavy metals in the environment during industrial development and the subsequent efforts of the post-industrial society to limit this pollution. Maximum measured metal concentrations increased by 3.5 (Pb), 3.8 (Cd), 1.7(Cu) and 2.0 (Zn) times relative to natural background concentrations. The relative late decrease of Pb concentration in the profiles, starting around 1975, relates to the ban of leaded gasoline in Switzerland. Actual metal concentrations are still far above the natural background levels.Resume : Analyse et datation de profils en Pb, Cd, Cu, Zn de sédiments lacustres provenant du lac des Quatre cantons, Suisse (bassin de Vitznau). Deux carottes parallèles de sédiments lacustres provenant du bassin de la Vitznau (lac des Quatre Cantons, Suisse) ont été échantillonnées et analysées en teneurs d'eau et en Pb, Cd, Cu et Zn. Les cinq profils sont caractérisés par deux anomalies à 12 et à 39 cm de profondeur. La première anomalie à 12 cm est liée aux éboulements successifs du flanc nord du 'Biirgenstock' situé à Obermatt qui a eu lieu en trois phases en 1963 et 1964. La deuxième anomalie (39 cm) est corrélée au glissement de terrain de la rivière Vitznau de 1674. Les deux taux de sédimentation moyens obtenus pour les périodes séparant ces deux événements sont de S1997 1964 = 0.041 g cm-2 y-1 et S1962/1674 = 0.025g cm-2. L'élévation du taux moyen plus récent témoigne de l'excès de matière organique déposée en liaison avec l'eutrophisation du bassin débutant en 1954. Les profils de métaux sont constants avant 1800, les concentrations respectives caractérisent ainsi le fond géochimique préindustriel: 37.9 ± 1.8 mg/kg de Pb, 0.53 ± 0.10 mg/kg de Cd, 33.0 ± 2.6 mg/kg de Cu, et 103.9 ± 5.5 mg/kg de Zn. De 1800 à 1950 les quatre concentrations croissent conjointement de façon exponentielle, suivi d'une diminution marquée à partir de - 1 965 qui perdure jusqu'à nos jours. Ces courbes témoignent donc de l'accroissement de l'émission diffusive des métaux de la société industrielle en phase de développement et de la diminution de cette même pollution dans le cadre des efforts entrepris dans ce sens par la société post-industrielle. Les concentrations maximales sont 3.5 (Pb), 3.8 (Cd), 1.7(Cu) et 2.0 (Zn) fois celles du fond géochimique. La diminution relativement tardive du Pb à partir de 1975 est liée à la substitution de combustibles plombés. Les concentrations actuelles sont loin d'avoir atteint les seuils préindustriels.Spadini Lorenzo, Sturm Michael, Wehrli Bernhard, Bott Markus. Analysis and dating of Pb, Cd, Cu, Zn sediment profiles from the Vitznau basin of Lake Lucerne (Switzerland) / Analyse et datation de profils en Pb, Cd, Cu, Zn de sédiments lacustres provenant du lac des Quatre Cantons, Suisse (bassin de Vitznau). In: Revue de géographie alpine, tome 91, n°1, 2003. Hydrosystèmes lacustres et changements environnementaux / Lake hydrosystems and environmental changes sous la direction de Laurent Astrade et Rachid Nedjaï. pp. 41-49

Analysis of the major Fe bearing mineral phases in recent lake sediments by EXAFS spectroscopy.

International audienc

Assessment of biofilm destabilisation and consequent facilitated zinc transport.

International audienceIn infiltration basins, such as in any kind of porous media, bacteria may form biofilms. When conditions induce destabilization of this biofilm, resulting colloids are transported by the hydraulic flow. Some studies have focused on the role played by these bacterial colloids in pollutants transport in soil. This study deals with the ability of Pseudomonas putida to retain zinc and investigates the facilitated transport of this metal. Batch and columns experiments have been carried out. Bacteria display a great affinity for zinc in batch experiments and facilitated transport have been highlighted in a small extent, for the moment. A scenario of stabilization/destabilization of the biofilm has been designed and may be employed for further investigations

Experimental study and modelling of the transfer of zinc in a low reactive sand column in the presence of acetate.

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Determination of mercury atmospheric origin in French Guianese soils.

International audienceMercury pollution is a preoccupying environmental problem affecting French Guiana ecosystems. Mercury (Hg) concentrations found in fei-rallitic soils of the dense Guianese forest are high and variable. Natural Hg geochemical background is the result of a long telm accumulation from two sources in the soil, in situ, weathering ofparental material and atmospheric inputs from oceans principally. Abnormally high levels of mercury are related to gold-mining activities. To evaluate the proportion of mercury from weathering processes and from atmospheric inputs, we used a mass balance calculation based on trace elements. This approach reveals that even in areas considered to be natural environments, the proportion of Hg derived from weathering appears to be negligible compared to the atmospheric origin. Soils located close to gold-mining sites are strongly affected by mercury pollution. Pellehatioll and accumulation of atmospheric inputs as well as Hg redistribution in soil profiles depend on the hydrodynamical propeliies, redox conditions and the quality and quantity of carrier phases. Key-words: Mercury, soils, atmospheric inputs, geochemical background, pollution, gold-mining