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Four cores of anoxic sediments were collected from the Seine estuary to assess the early diagenesis pathways leading to the
formation of previously reactive phase. Pore waters were analyzed for dissolved iron (Fe) and manganese (Mn) and different
ligands (e.g., sulfate, chloride, total inorganic carbon). The anoxic zone is present up to the first centimeter depth, in
these conditions the reduction of Mn and Fe oxides and SO4
2− was verified. The sulfate reduction was well established with a subsequent carbon mineralization in the NORMAI94 core. The
chemical speciation of Mn and Fe in the dissolved and solid phases was determined. For the dissolved phase, thermodynamic
calculations were used to characterize and illustrate the importance of carbonate and phosphate phases as sinks for Fe and
Mn. The ion activity product (IAP) of Fe and Mn species was compared to the solubility products (Ks) of these species. In
the solid phase, the presence of higher concentration of calcium carbonate in the Seine sediments is an important factor controlling
Mn cycle. The carbonate-bound Mn can reach more than 75% of the total concentration. This result is confirmed by the use of
electron spin resonance (ESR) spectroscopy. The reduction of Fe is closely coupled to the sulfate reduction by the formation
of new solid phases such as FeS and FeS2, which can be regarded as temporal sinks for sulfides. These forms were quantified in all cores as acid volatile sulfide
(AVS: FeS+ free sulfide) and chromium reducible sulfide (CRS: FeS2+elemental sulfur S0). 相似文献
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Adeline CharriauLudovic Lesven Yue GaoMartine Leermakers Willy BaeyensBaghdad Ouddane Gabriel Billon 《Applied Geochemistry》2011,26(1):80-90
Three sediment cores were collected in the Scheldt, Lys and Spiere canals, which drain a highly populated and industrialized area in Western Europe. The speciation and the distribution of trace metals in pore waters and sediment particles were assessed through a combination of computational and experimental techniques. The concentrations of dissolved major and trace elements (anions, cations, sulfides, dissolved organic C, Cd, Co, Fe, Mn, Ni, Pb and Zn) were used to calculate the thermodynamic equilibrium speciation in pore waters and to evaluate the saturation of minerals (Visual Minteq software). A sequential extraction procedure was applied on anoxic sediment particles in order to assess the main host phases of trace elements. Manganese was the most labile metal in pore waters and was mainly associated with carbonates in particles. In contrast, a weak affinity of Cd, Co, Ni, Pb and Zn with carbonates was established because: (1) a systematic under-saturation was noticed in pore waters and (2) less than 10% of these elements were extracted in the exchangeable and carbonate sedimentary fraction. In the studied anoxic sediments, the mobility and the lability of trace metals, apart from Mn, seemed to be controlled through the competition between sulfidic and organic ligands. In particular, the necessity of taking into account organic matter in the modelling of thermodynamic equilibrium was demonstrated for Cd, Ni, Zn and Pb, the latter element exhibiting the strongest affinity with humic substances. Consequently, dissolved organic matter could favour the stabilization of trace metals in the liquid phase. Conversely, sulfide minerals played a key role in the scavenging of trace metals in sediment particles. Finally, similar trace metal lability rankings were obtained for the liquid and solid phases. 相似文献
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Ramond JB Berthe T Lafite R Deloffre J Ouddane B Petit F 《Marine pollution bulletin》2008,56(6):1168-1176
The Seine estuary (France) is one of the world's macrotidal systems that is most contaminated with heavy metals. To study the mercury-resistant bacterial community in such an environment, we have developed a molecular tool, based on competitive PCR, enabling the quantification of Gram-negative merA gene abundance. The occurrence of the Gram-negative merA gene in relation with the topology (erosion/deposit periods) and the mercury contamination of three contrasted mudflats was investigated through a multidisciplinary approach and compared with a non-anthropized site (Authie, France). The higher abundance of the Gram-negative merA gene in the Seine estuary mudflats indicates a relationship between the degree of anthropization and the abundance of the merA gene in the mudflat sediments. In the Seine mudflats, the maxima of abundance are always located in fresh sediment deposits. Therefore, the abundance is closely related with the hydrosedimentary processes, which thus seem to be determining factors in the occurrence of the Gram-negative merA gene in the surface sediments of the Seine's mudflat. 相似文献
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The Seine’s estuary (France) waters are the receptacle of effluents originating from wastewater treatment plants (WWTP). In this estuary, mudflats are deposition zones for sediments and their associated contaminants, and play an essential role in the mercury (Hg) biogeochemical cycle mainly due to indigenous microorganisms. Microcosms were used to assess the impact of WWTP-effluents on mercury methylation by monitoring Hg species (total dissolved Hg in porewater, methylmercury and total mercury) and on microbial communities in sediments. After effluent amendment, methylmercury (MeHg) concentrations increased in relation with the total Hg and organic matter content of the WWTP-effluents. A correlation was observed between MeHg and acid-volatile-sulfides concentrations. Quantification of sulfate-reducing microorganisms involved in Hg methylation showed no increase of their abundance but their activity was probably enhanced by the organic matter supplied with the effluents. WWTP-effluent spiking modified the bacterial community fingerprint, mainly influenced by Hg contamination and the organic matter amendment. 相似文献
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This work analyzes the stone superficial deterioration of some monuments in Rabat city. The rock is a calcarenite with porous
texture, rich in calcium carbonates and fossils. The techniques used to study the surfaces altered by blackening or black
crusts, are the SEM equipped with EDX microprobe, the X-ray diffraction, and the analysis of the soluble salts by ionic chromatography
for anions and flame spectrometer for cations. They reveal significant contents of calcium sulphates, mainly gypsum, often
associated with sodium chlorides. These salts known to have a destructive effect on the calcareous stones seem to be originated
from the contamination by atmospheric pollutants, particularly sulfur dioxide, and by the marine sprays. 相似文献
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