20 research outputs found
MĂ©thodologie dâune recherche palĂ©oenvironnementale en archĂ©ologie prĂ©ventive : lâexemple du site de Kerkhove stuw (Belgique)
En archéologie comme dans les études paléoenvironnementales, la phase de terrain est essentielle, car elle constitue la
collecte des donnĂ©es et du matĂ©riel qui vont servir aux Ă©tudes en laboratoire. Cette Ă©tape est dâautant plus dĂ©licate en
contexte préventif que le temps est un facteur clé. La méthodologie employée lors des fouilles préventives du site de Kerkhove
Stuw a permis une Ă©tude palĂ©oenvironnementale approfondie, apportant de nouvelles informations sur lâĂ©volution
du paysage de la vallĂ©e de lâEscaut depuis la fin du WeichsĂ©lien
Predicting effective diffusion coefficients in mudrocks using a fractal model and small-angle neutron scattering measurements
The determination of effective diffusion coefficients of gases or solutes in the waterâsaturated pore space of mudrocks is time consuming and technically challenging. Yet reliable values of effective diffusion coefficients are important to predict migration of hydrocarbon gases in unconventional reservoirs, dissipation of (explosive) gases through clay barriers in radioactive waste repositories, mineral alteration of seals to geological CO2 storage reservoirs, and contaminant migration through aquitards. In this study, smallâangle and very small angle neutron scattering techniques have been utilized to determine a range of transport properties in mudrocks, including porosity, pore size distributions, and surface and volume fractal dimensions of pores and grains, from which diffusive transport parameters can be estimated. Using a fractal model derived from Archie's law, we calculate effective diffusion coefficients from these parameters and compare them to laboratoryâderived effective diffusion coefficients for CO2, H2, CH4, and HTO on either the same or related mudrock samples. The samples include Opalinus Shale from the underground laboratory in Mont Terri, Switzerland, Boom Clay from a core drilled in Mol, Belgium, and a marine claystone cored in Utah, USA. The predicted values were compared to laboratory diffusion measurements. The measured and modeled diffusion coefficients show good agreement, differing generally by less than factor 5. Neutron or Xâray scattering analysis is therefore proposed as a novel method for fast, accurate estimation of effective diffusion coefficients in mudrocks, together with simultaneous measurement of multiple transport parameters including porosity, pore size distributions, and surface areas, important for (reactive) transport modeling
Mapping of the Eltanin impact area in the South-East Pacific
Two Polarstern expeditions were conducted in 1995 (ANT-XII/4) and 2001 (ANT-XVIII/5a) to the Bellingshausen Sea and Amundsen Sea and the suspected Eltanin meteorite impact in the SE-Pacific. A survey of the sediment distribution and its acoustic structure along the cruise track was performed. The seafloor topography was sampled using the multibeam sonar system Hydrosweep DS2 which operates on a frequency of 15.5 kHz. The resulting AWI Bathymetric Chart of the Eltanin Meteorite Impact Area is based on a Digital Terrain Model of this area. The mapping was performed using ArcGIS. The Eltanin impact area which covers the 4.100 m high Freden Seamount is visualized by one overview sheet of the scale 1:200,000 and four 1:100,000 subsheets