Anaerobiosis in saturated soil aggregates : modelling and experiment
Résumé
A model of anaerobiosis based on gas diffusion and microbial respiration is proposed for soil aggregates. Unlike previous models, it accounts for the dependency of O-2 consumption on O-2 and CO2 concentrations and, consequently, on chemical reactions of CO2 in soil solution. The model is tested with experimental data of respiration and O-2 distribution within spherical remoulded aggregates of different sizes saturated with water. Most of the model parameters were estimated experimentally. Fick's law could describe O-2 diffusion inside the saturated aggregates. The model agreed well with O-2 profiles measured soon after saturation. Later, the model underestimated anaerobiosis, probably because of changes in radial distribution of microbial activity inside the aggregates. Respiration as a function of O-2 concentration was satisfactorily described by the model. Nevertheless, each size of aggregate was analysed separately because of an apparent relation between size and maximal aerobic respiration. This seems to be associated with a non-homogeneous distribution of aerobic respiration. The model represents an improvement on those currently used to estimate anaerobiosis inside aggregates.