Recurrent recovery of Pseudomonas oryzihabitans strains in a karstified chalk aquifer

International audiencePseudomonas oryzihabitans is an uncommon pathogen that may cause catheter-associated infections, particularly in immunocompromised patients. Although it has been isolated from environment, the source of human infection is not well documented. In the present study, 14 isolates of P. oryzihabitans were recovered over a 28-month period from a karstified chalk aquifer, allowing to advance that distributed natural water could be a source of contamination. Microbiological analyses showed that the bacterium was mainly associated with suspended particulate matters. To investigate the clonality of P. oryzihabitans environmental isolates, 16S rRNA gene sequencing, antibiogram and randomly amplified polymorphic DNA (RAPD) typings were performed. Results demonstrated (i) the presence of at least three clones within the aquifer and (ii) that the presence of the bacterium in groundwater is not only the result of a biofilm bloom but also of an exogenous contamination

Polyphase karst system in Cretaceous chalk and calcarenite of the Belgian-Dutch border .

International audienceAlong the Belgian-Dutch border, underground and surface quarries dug in Cretaceous calcarenite and chalk intersect many karst features as well as deep large nodes of weathered rock. Their observation allows the reconstruction of the genesis of an original karst system resulting from the merging of initially independent endokarsts and exokarsts. Deep weathering has developed within the Cretaceous formations, creating nodes of weathered chalk and closed cavities. These phenomena are expanded over time and can form interconnected voids. Near the surface, solution pipes are generated under the coarsest deposits of a fluvial terrace capping the Cretaceous formations. These pipes develop vertically and may be related to the progressive lowering of the water table in connection with the incision of the Meuse valley. Some of these phenomena cut up the older endokarsts and organize complex systems of out-flow within the chalk

Artificial tracer Tests interpretation using transfer function approach to study the Norville karst system

International audienceKarstic aquifers are known for their high degree of nonlinearity and non-stationarity in their hydrodynamic behaviour. We used a transfer function approach (TFA) to interpret artificial tracer tests in Norville karst system (Normandy, France). The system’s behaviour is modelled as a conceptual reservoir with an assumed transfer function containing an ‘intrinsic’ part and a ‘boundary conditions dependent’ part. Additionally, a relationship between spring discharge and residence time distribution characteristics can be formulated. This constitutes new perspectives for testing pollution scenarios