An in situ experimental bag method to study the influence of environmental factors on uranium mobilization and preconcentration in soils

An in situ bag method was used to study, in natural soil conditions, the U solubilization from rocks and minerals and also the U fixation and preconcentration by soil constituents. By this means, interesting data are obtained. U solubilization depends not only upon the rock and mineral nature but also upon the humus type, induced by the nature of the vegetation and its associated microbial activity. Clays and non-transformed plant materials (cellulose, lignin) are not appropriate sinks for U, but ferric oxyhydroxides or microbial metabolites and microbial constituents appear as very efficient sinks that occur in preconcentration processes in soils. The in situ fixed amounts of U are lower than those obtained in laboratory experiments, but probably more realistic. Finally, this experimental method seems of great interest to study the U (but also other metals) behaviour in natural conditions. 16 refs.; 8 tabs