Geochemistry and radionuclide content of sediment and water samples obtained from the Ob and Irtysh river, Russia

This paper reports the results of the investigations of 2006-2007 on the distribution and migration forms of artificial radionuclides and chemical elements in the Ob-Irtysh water system. Three regions were studied. One of them is a local segment of the Ob River upstream from the confluence with the Irtysh River; its investigation allowed us to estimate the general radioecological state of the aquatic environment affected by the activity of the Tomsk 7 plant. The second region is a local segment of the Irtysh River upstream from its confluence with the Ob River, where the influence of emissions from the NPO Mayak could be estimated. The third region is the water area of the Ob River after its confluence with the Irtysh River. It characterizes the real level of radioactive and chemical contamination of the middle reaches of the Ob River. In order to explain horizontal variations in the distribution of radionuclides in the upper layer of bottom sediments collected at various sites, the results of sorption-kinetic experiments with radioactive tracers in the precipitate-solution system were used. The investigation of the migration forms of trace elements and radionuclides occurring in river water was based on the method of tangential-flow membrane filtration. Chemical element contents were determined in 400-ml water samples. A set of Millipore polysulfone membranes with pore sizes of 8, 1.2, 0.45, 0.1, and 0.025 µm was employed. Taking into account the ultralow specific concentrations of radionuclides in the water, they were analyzed in 300-500 litre samples using Millipore polysulfone membranes with pore sizes of 0.45 µm and 15 kDa. This allowed us to estimate the percentages of cesium-137 and plutonium-239, 240 in the suspended particulate fraction, colloids, and dissolved species.

El modelo médico hegemónico y su reproducción en el perfil de médico que promueve la Fac. Cs. Médicas de la U.N.L.P

Fil: Vetere, Pablo Emiliano. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Bötcher, Nikolaus; Hausberger, Bernd; Ibarra, Antonio (coords) Redes y negocios globales en el mundo ibérico, siglos XVI-XVIII, Madrid, Frankfurt, 2011, 312 páginas Iberoamericana, Veruvert, Bibliotheca IberoAmericana, 137

Fil: Mallo, Silvia Cristina. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

El modelo médico hegemónico y su reproducción en el perfil de médico que promueve la Fac. Cs. Médicas de la U.N.L.P

Fil: Vetere, Pablo Emiliano. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Bötcher, Nikolaus; Hausberger, Bernd; Ibarra, Antonio (coords) Redes y negocios globales en el mundo ibérico, siglos XVI-XVIII, Madrid, Frankfurt, 2011, 312 páginas Iberoamericana, Veruvert, Bibliotheca IberoAmericana, 137

Fil: Mallo, Silvia Cristina. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Physical properties and elastic constants of ODP Holes 137-504B and 140-504B upper crustal rocks

Seismic velocities have been measured at confining pressures of 100 MPa and 600 MPa for sheeted dike samples recovered during Ocean Drilling Program Legs 137 and 140. The compressional- and shear-wave velocities show an increase with depth at Hole 504B, which is in sharp contrast to the atmospheric pressure velocity measurements performed as part of the shipboard analyses. Rocks exposed to different types of alteration and fracture patterns show distinct changes in their physical properties. The seismic reflectors observed on the vertical seismic profile (VSP) experiment performed during Leg 111 may have been caused by low velocity zones resulting from alteration. The amount of fracturing and hydrothermal alteration in several zones also may have contributed to the acoustic impedance contrast necessary to produce the E5 reflector. Poisson's ratios calculated from laboratory velocity measurements show several low values at depths ranging from 1600 mbsf to 2000 mbsf, which tends to follow similar trends obtained from previous oceanic refraction experiments. A comparison of physical properties between samples recovered from Hole 504B and ophiolite studies in the Bay of Islands and Oman shows a good correlation with the Bay of Islands but significant differences from the measurements performed in the Oman complex.