Abstract
In this work, we have analysed the geographical distribution of the U-isotopes concentrations in the waters of the Almonte-Marismas aquifer, located at the south of Spain. During the year 2000, a systematic sampling was carried out, being all the samples analysed for U isotopes by alpha-particle spectrometry, both in the dissolution and suspended phases. From the spatial distribution obtained in this detritic aquifer for the dissolved Uranium and for the U equilibrium distribution coefficients, it has been possible to delimit its main oxidised and reduced zones. It has been then demonstrated, how the determination of Uranium isotopes concentrations over a detritic aquifer is a powerful and elegant tool to understand some basic processes that govern the geochemical behaviour of these natural systems.