Claude Latouche

Long term behaviour and degradation kinetics of tributyltin in a marina sediment

One-meter sediment cores sampled in a marina have been submitted to extensive characterization and organotin speciation. Geochemical homogeneity has been demonstrated. Butyltin species are present at all depths with a predominance of TBT or MBT in the upper or lower layers, respectively. Seasonal variations of butyltin compounds have been identified and together with a knowledge of local conditions we estimate the sediment layers represent 14 years of deposition. A first order multi-step kinetic model of the sequential degradation of TBT in, successively, DBT, MBT and Sn (IV) is proposed. The half-life of TBT was estimated (on a 14-year period) to be 2.1 years and those of DBT and MBT (on a 5-year period) 1.9 and 1.1 years, respectively.

Cadmium in the gironde fluvioestuarine system: Behaviour and flow

Abstract Major cadmium contamination of molluscs was discovered in the Gironde estuary. Studies were then undertaken on biota and on particulate and dissolved phases. Biota was studied by monitoring populations of oysters and mussels transplanted from uncontaminated areas into the Gironde. Studies on particulate and dissolved phases were carried out within the estuary, on the inner shelf, in Marennes-Oleron Bay, and in the drainage basin of the Gironde. It appears that: (i) the estuarine particulate stock, with its long residence time, plays a part in particulate-dissolved transformation, and thus has an effect on chemical conditions in the lower estuary and the coastal zone; (ii) the dissolved cadmium concentrations downstream can explain the concentrations measured in the oysters; (iii) the contamination is recent, and originates from the drainage basin; (iv) a geochemical cadmium budget in the Gironde has been formulated and is discussed.

Late Quaternary sedimentation between the Gibbs Fracture and the Greenland Basin: Mineralogical and geochemical data

The geochemical study of core samples taken between the Gibbs Fracture zone and the south of the Greenland Basin leads to an understanding of the sedimentogenesis of this region since the last interglacial stage. By demonstrating well-defined mineralogical and chemical assemblages, it is possible to suggest an origin for sediments and the direction of flow. Two major families of influx, one of a petrographically acidic nature, the other basic, observed in the neighbouring basins, are distinguished; variations in their relative importance are linked to climate and hydrology. The basic phase is represented chiefly by an inflow of volcanic detritus, derived from the erosion of Iceland and the Faeroes. Iron, titanium and smectite distribution patterns indicate that Iceland is their probable source, while nickel and copper would come from the Faeroe islands. In the south of the basin (Gibbs Fracture), the basic deposition reaches 10 cm103yrs. The acidic phase is brought by ice-rafting during the colder period and by bottom currents during the warmer period. In the post-glacial its contribution reaches 30 cm103yrs as far away as the Gibbs Fracture Zone.

ND-SR ISOTOPIC COMPOSITION OF PRESENT-DAY SEDIMENTS FROM THE GIRONDE ESTUARY, ITS DRAINING BASINS AND THE WESTGIRONDE MUD PATCH (SW FRANCE)

Abstract The isotopic composition of silty clay sediments in the Gironde Estuary, which were sampled between 1986 and 1995, shows homogeneity. The sediments from the Garonne and the Dordogne Rivers, including the tributary Isle River, are well mixed within the turbidity maximum zone. The composition of the clay solid load of the upstream Garonne River was also homogeneous between 1985 and 1990, even though there is a large diversity and temporal variabilities in the floods of the many tributaries of this river. Isotopic data were used to calculate the silty clay contribution of the two main rivers to the total estuarine stock: 70% of the total material is brought in by the Garonne River and 30% by the Dordogne River, including its tributary (the Isle River). The same isotopic signature can be observed in the present-day sediments and suspended materials of the WestGironde mud patch, on the adjacent Aquitaine continental plateau.

Caractéristiques des argiles hydrothermales de la Martinique — Petites Antilles Françaises

Abstract Martinique constitutes an island of the active volcanic arc of the “Petites Antilles” and is situated at the divergent point between the old and recent arcs. The paleogeographical context of the old arc, partially elaborated in a submarine to subaerial environment, is favorable to the development of hydrothermal formations. The mineralogical and chemical characteristics of three types of hydrothermal clay, derived from dacitic rocks and situated respectively in Bellefontaine, Trois-Ilets and on Caravelle Peninsula were determined. These formations do not show the same assemblage of clay minerals: very well crystallized smectites, can be largely dominant (80%) as in Bellefontaine, or illites as in Trois-Ilets, or celadonites as on the Caravelle Peninsula; illites and celadonites are never associated within climatic alterites from the island. Trace element assemblages point out strong concentrations of Cl, S, Cu, Zn, As, Pb etc., which are evidences for hydrothermal enrichments. Every type of weathering is characterized by a particular association that shows variable chemical compositions of the hydrothermal fluids circulating within the deep fractures, as well as the physical conditions in which these recrystallizations occurred. The 87 Sr 86 Sr ratios show that the formation of these clay minerals is accompanied by an enrichment in radiogenic Sr. Clay formations of the Trois-Ilets could prove Upper Miocene deep hydrothermal activity.

The nature and origin of smectites in the Kerguelen-Heard Archipelagoes of the southern Indian Ocean.

Abstract The clay phases of the Quaternary volcanics, soils and sediments from the northern part of the Kerguelen-Heard Plateau, southern Indian Ocean, are essentially well-crystallized smectites. The origin of these smectites was studied based on variations in their mineralogy and their different stages of development in the different environments. This study indicates: (1) Two major groups of smectites occur in the hydrothermal alteration products of the Kerguelen Island volcanic formations Mg s.s. and Fe-Mg saponites of the basalts, and Al-Fe and Al beidellites in the other formations. In the soils formed on the volcanic substratum, the well-crystallized smectites are mainly of the Al beidellite type and, secondarily, of the Al-Fe beidellite type. (2) In the Morbihan Gulf sediments, the well-crystallized smectites are dominant and of the Al-Fe and Al beidellite type: these smectites are inherited from the volcanic formations and soils of the Kerguelen Islands. (3) In the Quaternary sediments of the Kerguelen-Heard Plateau, the well-crystallized and relatively abundant smectites are of the Mg-rich, Al nontronite type. The absence of related links with the Kerguelen Island smectites, the substantial dissolution of the siliceous tests, the degree of silica saturation of the water context and the occurrence of glauconite, the first stage of formation being a rich-Mg ferriferous smectite, supports the hypothesis of an authigenous origin for these smectites rather than originating by inheritance from the volcanic islands.

Origin and pathways of Cadmium Contamination in the Gironde estuary, Garonne river and tributaries.

Publisher Summary This chapter investigates the characteristics, effects on biota, origin, and transfer processes of Cd pollution in the Gironde estuary. Cd mainly originates from a former industrial zone of the drainage basin localized about 400 km upstream to the inlet. At the estuary mouth, a major cadmium contamination of mollusks was first recognized in 1979 in the framework of the National Observation Network, the office in charge of the monitoring of the quality of the French marine environment. Detailed studies were then undertaken on biota and on solid and dissolved media. Biota was investigated by monitoring the populations of oysters and mussels transplanted from uncontaminated areas into the inlet of Gironde. Cd concentrations in oysters reached high levels in only six months. The kinetics of Cd accumulation appeared higher in summer than winter. Downstream, suspended matter (SM) undergoes major changes facilitated by a long residence time of SM within the brackish waters of the estuary. Cd and many other associated metals pass, for a large part, into solution under the effects of macrotidal-type estuarine processes. After solubilization, the metals are concentrated by mollusks of the estuary mouth according to the kinetics of accumulation studied on the basis of an in situ experiment.

Evolution du Pb, Zn, Cu, Ni et As dans le Bassin d'Arcachon (France). Impact de la biomasse végétale sur la géochimie d'un environment lagunaire

Abstract The concentration of metals as Pb, Cu, Ni and As in suspended matters and sediments during 14 years shows for suspended matters and sediments that: Zn and Cu are increasing, Pb and As decreasing and Ni is stabilised. The evolution of the suspended matter can be explained by the quantitative evolution of algae and phanerogams during these last 14 years. The biomass evolution, which resulted in environmental nutrient contribution, intensifies the exchange factors of Pb and As in the lagoon. These remarks, beyond their local interests, provide notions of sedimentary environment model opposed to a polluting environment constituted by nautic tourism and a large area of monoculture (corn).

Nature et origine des formations argileuses d'un environnement de source thermo-minérale aux îles Kerguelen (Océan Indien Austral)

Abstract The clay mineralogical and geochemical study of a hot-mineral spring environment from the Kerguelen Islands (southern Indian Ocean) permits to distinguish three types of clay minerals in relationship with the chemical composition of the spring waters with temperatures near 60°C and the altered rock petrography: irregular talc-saponite mixed-layer minerals of stevensite type, highly enriched in Br, S and Ga from the peat near the spring; smectites of montmorillonite-beidellite type enriched in magnesium in the peat developed near the spring; and halloysites formed from amorphous products resulting from trachytic pumice alteration, enriched in As, Ba, S and Cs.