Influences de l'oxydation et de la biodégradation anaerobie sur la matière organique de l'argile oligocene de Boom (Mol, Belgique): conséquences sur la formation d'especes organiques hydrosolubles

In the context of geological disposal, it is important to assess the consequences of galleries excavation on the properties of the host rock. Therefore, this work deals with studies about the consequences of excavation‐induced disturbances on the fossil organic matter of Boom Clay. The particular focus of this study is the effects of air oxidation and anaerobic biodegradation on the OM. The experiments dealing with the effects of air oxidation have combined studies of artificial oxidized samples (artificial series) and samples altered in the gallery of the underground laboratory (natural series). These experiments focus on kerogen, organic fraction extractable by organic solvent (EOM) and water‐soluble fraction (DOM). It was shown that air oxidation induced a significant increase in the amount of DOM and a major change in the chemistry of the EOM and DOM characterized by the formation of low molecular weight oxygenated molecules. Moreover, comparison between water extracted from altered samples and piezometers shows that the water of the site is not affected by oxidation processes. The piezometer water samples are similar to that extracted from non‐altered samples. It seems that anaerobic biodegradation is not a major process in the context of disturbances induced by the excavation.