Interaction entre les activités du 137Cs et la matière organique dans les sols du sous bassin versant de Bougoula en zone soudanienne du Mali

Rural development, water resources management and more generally environmental protection programs need decision support tools. There is an urgent need to find simple, reliable and inexpensive diagnostic methods. The cesium 137 (137Cs) method has an advantage of allowing the quantification of the erosion / sedimentation balance. It is accepted that 137Cs can attach to fine soil particles. However, the intervention of different soil constituents (organic matter and clay) in the fixation of 137Cs is a controversial subject. The 137Cs activity enables to tracking movement of soil particles in order to identify eroded and deposition zones. It is within this context that this research was initiated in order to specify the interactions of organic matter with the 137Cs specific activity. The organic matter was determined from the carbon level by the Anne method and the 137Cs by gamma spectrometry. Results show variations in the organic matter and 137Cs rate. The organic matter and 137Cs contents in the surface layers are much correlated (r² = 0.77). In addition, results show that in depression zones where fine particles accumulate, there is an increase in the organic matter content (more than 1%) and the 137Cs activity (more than 500 Bq / m2 ) unlike the upstream models where there is very little organic matter (less than 1%) and a low 137Cs activity (less than 400 Bq / m2 ). However, the local micro depressions on the trays are very rich zones in organic matter and 137Cs activity