Influence of transient flow on the mobility of strontium in unsaturated sans columns

Titre du congrès :TRACER 4th International Conference on Tracers and Tracing Methods Ville du congrès :Autrans Date du congrès :03/10/2006

The prediction of a contaminant's fate and its behavior in soils and the vadose zone is important for the environmental evaluation and possible rehabilitation of soils occupied by industrial installations in operation or during dismantling. Owing to the complexity of the hydro-geochemical phenomena occuring in the unsaturated zone, reactive transport of contaminants is often simplified, mainly taking into account with a retardation factor and average constant flow conditions. Field and loboratory experiments are in progress world-wide to improve our understanding and reduce prediction model's uncertainties. Some recent experiments were focussed on the transport of caesium 137 and strontium 90 in sand columns in unsaturated steady state hydraulic conditions with constant geochemical conditions (Szenknect, 2003). One of the main results is that transport of such porous media. However, in natural conditions, hydraulic behaviour of soils is highly transient in space and time. The purpose of this work is to study strontium transport with the same sand columns and geochemical conditions, but under transient unsaturated hydraulic conditions. First we determined hydraulic conductivity and water retention relationships as a function of water content of the porous media. We then studied the influence of sequences of infiltration/redistribution events on the transport of strontium along the column. Results we compared to those obtained under equivalent steady state hydraulic conditions.