A Raman spectroscopic study of arsenite and thioarsenite species in aqueous solution at 25°C

The Raman spectra of thioarsenite and arsenite species in aqueous solution were obtained at room temperature. Solutions at constant ΣAs + ΣS of 0.1 and 0.5 mol kg(-1 )were prepared with various ΣS/ΣAs ratios (0.1–9.0) and pH values (~7–13.2). Our data suggest that the speciation of As under the conditions investigated is more complicated than previously thought. The Raman measurements offer evidence for at least six separate S-bearing As species whose principal bands are centered near 365, 385, 390, 400, 415 and 420 cm(-1). The data suggest that at least two different species may give rise to bands at 385 cm(-1), bringing the probable minimum number of species to seven. Several additional species are possible but could not be resolved definitively. In general, the relative proportions of these species are dependent on total As concentration, ΣS/ΣAs ratio and pH. At very low ΣS/ΣAs ratios we also observe Raman bands attributable to the dissociation products of H(3)AsO(3)(aq). Although we were unable to assign precise stoichiometries for the various thioarsenite species, we were able to map out general pH and ΣS/ΣAs conditions under which the various thioarsenite and arsenite species are predominant. This study provides a basis for more detailed Raman spectroscopic and other types of investigations of the nature of thioarsenite species

Development and Exploitation of Low Enthalpy Geothermal Systems, Example of "The Dogger" in the Paris Basin, France

A feature of French geothermal engineering is the development of industrial projects in normal gradient, non-convective areas. The economic feasibility of exploiting wells producing between 150 and 350 m{sup 3}/h at temperatures from 55° to 85° from depths of 1,500 to 2,000 meters, in sedimentary basins with normal gradient, for direct heat production has been proved by 50 plants providing heating for over 500,000 people during the last few years. This opens new possibilities for geothermal energy development the world over, in particular for areas where heat consumption is higher than 2,500 Tons oil equivalent (Toe)/year over several square kilometers. The recent and rapid development of geothermal projects in France, in particular in the Paris Basin has provided much more information on the characteristics of the Jurassic Dogger, which is the unit tapped by geothermal doublets (one production and one injection well). Detailed study of the Dogger reservoir in the Paris Basin is one of the main objectives of the IMRG research and development program drawn up in 1983. The preliminary results presented here are oriented towards (1) improved knowledge of the potential geothermal resources, and (2) analysis of optimum development conditions. 1 tab., 7 refs., 9 figs

Gas Geochemistry of the Dogger Geothermal Aquifer (Paris Basin, France)

The low enthalpy program developed in the Paris Basin provides the opportunity for studying the gas geochemistry of the calcareous aquifer of the Dogger. Hydrocarbons and CO{sub 2} are mainly biogenic, He displays high concentrations. He, Ar and N{sub 2} have multiple origins (radioactive decay, atmospheric migration, biochemical processes). The distribution of the gases in the zones of the basin varies in relation to the general chemistry, sedimentology and hydrodynamics. The gas geothermometers do not apply to this environment but useful estimations of the redox potential of the fluid can be derived from CO{sub 2}/CH{sub 4} and N{sub 2}/NH{sub 4}{sup +} ratios. H{sub 2} and H{sub 2}S are involved in corrosion processes and scaling in the pipes. 12 refs., 3 figs., 2 tabs

Qarassa, un site du Bronze ancien et moyen en Syrie du Sud. Travaux 2007-2010.

À la suite d’une prospection régionale du plateau basaltique du Leja, le site de Qarassa a été choisi pour la fouille en raison de sa représentativité chronologique du Natoufien à l’âge du Fer qui en fait la première référence chronostratigraphique longue pour la zone basaltique. Le tell sud de Qarassa est occupé du milieu du IVe jusqu’au deuxième quart du Ier millénaire. On propose ici une synthèse des résultats de la fouille des niveaux du Bronze ancien de cette agglomération fortifiée

Qarassa, un site du Bronze ancien et Moyen en Syrie du sud.: Travaux 2007-2010

Near East ; Early Bronze age ; Middle Bronze age ; urbanism ; stratigraphyInternational audienceFollowing the regional survey of the Leja's basaltic plateau, the excavation of Qarassa was decided because this site occupied from the Natufian to the Iron Age becomes a major chrono-stratigraphic reference for the basaltic area of southern Syria. The southern tell at Qarassa is occupied from the mid 4th to the second quarter of the 1st mill. We give here a first synthesis of the excavation's results about the Early Bronze Age fortified agglomeration.À la suite d'une prospection régionale du plateau basaltique du Leja, le site de Qarassa a été choisi pour la fouille en raison de sa représentativité chronologique du Natoufien à l'âge du Fer qui en fait la première référence chronostratigraphique longue pour la zone basaltique. Le tell sud de Qarassa est occupé du milieu du IVe jusqu'au deuxième quart du Ier millénaire. On propose ici une synthèse des résultats de la fouille des niveaux du Bronze ancien de cette agglomération fortifiée