Temporal variability of gas seeps offshore New Zealand: multi-frequency geoacoustic imaging of the Wairarapa area, Hikurangi margin

Cold seeps on Opouawe Bank, situated in around 1000 m water depth on the Hikurangi Margin offshore North Island. New Zealand, were investigated using multibeam bathymetry, 75 and 410 kHz sidescan sonar imagery, and 2–8 kHz Chirp sediment echosounder data. Towed video camera observations allowed ground-truthing the various geoacoustic data. At least eleven different seep locations displaying a range of seep activity were identified in the study area. The study area consists of an elongated, northward-widening ridge that is part of the accretionary Hikurangi Margin and is well separated from direct terrigenous input by margin channels surrounding the ridge. The geoacoustic signature of individual cold-seep sites ranged from smooth areas with slightly elevated backscatter intensity resulting from high gas content or the presence of near-surface gas hydrates, to rough areas with widespread patches of carbonates at the seafloor. Five cold seeps also show indications for active gas emissions in the form of acoustic plumes in the water column. Repeated sidescan sonar imagery of the plumes indicates they are highly variable in intensity and direction in the water column, probably reflecting the control of gas emission by tides and currents. Although gas emission appears strongly focused in the Wairarapa area, the actual extents of the cold seep structures are much wider in the subsurface as is shown by sediment echosounder profiles, where large gas fronts were observed

Caractérisation, simulations expérimentales et thermodynamiques de l'altération de déchets vitreux (les scories de première fusion de plomb et de zinc)

Depuis plus de 50 ans, l'usine Métaleurop de Noyelles-Godault (Nord) produit du plomb, du zinc et des déchets associés (scories, poussières). Stockés en crassier, dispersés dans les sols ou l'atmosphère, ces déchets peuvent relarguer des éléments nocifs (Pb, Zn, Cd) lors de leur altération. Ce travail a porté sur la caractérisation et la simulation expérimentale et thermodynamique de l'altération des scories de première fusion de plomb et de zinc de cette usine. Une caractérisation des scories fraîches (DRX, MEB-EDS, Microsonde électronique, RAMAN) a d'abord été menée. Les scories sont composées d'un verre alumino-silicaté riche en Fe, Ca, Pb, Zn dans lequel sont dispersés des spinelles et des goutelettes de plomb. La scorie de zinc présente également des sulfures et un assemblage à fer métal, sulfures et composés métalliques de As, Sn, Sb, Ni, Cu, Z, et Fe. La nature des minérais, des produits secondaires et des fondants employés ainsi que les différents traitements métallurgiques (grenaillage du laitier) contrôlent les caractères pétrophysiques des scories. L'altération naturelle a ensuite été étudiée sur des scories sur un crassier depuis environ 10 ans. Intense dans la scorie de zinc, elle montre une dissolution des assemblages métalliques, des sulfures et des billes de plomb. L'acidité engendrée par la dissolution des sulfures entraîne localement la dissolution du verre et une mobilisation des métaux. Le fer re-précipite sous forme d'oxy-hydroxydes (x-FeOOH), qui fixent les métaux (Pb, As, Zn) mais aussi les sulfates. Le plomb est contrôlé par la précipitation d'oxydes (litharge, massicot), de carbonates (cérusite et hydrocérusite) et d'oxy-sulfates (xPbO, PbSO4). Des essais de lixiviation de 300 jours pour deux pH acides en système fermé ont simulé expérimentalement l'altération des scories. Pour ces deux pH initiaux, les concentrations en solution sont faibles et les produits ...LILLE1-BU (590092102) / SudocSudocFranceF

Surcharge pondérale des élèves de 6ème scolarisés en Languedoc-Roussillon (prévalence, évolution et facteurs associés)

MONTPELLIER-BU Médecine UPM (341722108) / SudocMONTPELLIER-BU Médecine (341722104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

The Stimulation of Nitrification in an Organically Enriched Soil by Zeolitic Tuff and its Effect on Plant Growing

The adsorption and ion-exchange properties of natural zeolite minerals such as phillipsite, clinoptilolite and mordenite are well studied and these microporous minerals are known to have a high selectivity towards the ammonium ion. Natural zeolites are often found as alteration products of volcanic glass, in deposits of volcaniclastic sediment. In such rocks they are very abundant and commonly exceed 80 percent of the mineral assemblage. Due to their high selectivity towards ammonium ions, rocks containing these minerals can be used to adsorb ammonia from sewage and organic farm waste. It has now been found that a composted mixture of the crushed zeolitic tuff and organic waste will enhance nitrification in soils, when added as an amendment. During composting ammonia, derived from the biological degradation of the organic waste, is adsorbed and ion-exchanged by the zeolite minerals present in the mixture. When added to a soil, nitrification occurs as a result of oxidation of the ammonium ions, first to nitrite and then further to nitrate, together with the production of protons. These reactions were studied in a time-course experiment using the analysis of aqueous leachates taken from untreated and amended soil substrates. Nitrification trends were observed and a linear relationship was found between the electrical conductivity (EC) and the nitrate concentration of the leachates; demonstrating how the ionic mobility of the substrate porewater increases with increase in the degree of nitrification. A comparison of plant growth in substrates without zeolitic tuff with those amended with the organo-zeolitic mixture, showed that plant growth in the amended soil is greatly increased