ANAEROBIOSIS IN SATURATED SOIL AGGREGATES - MODELING AND EXPERIMENT

A model of anaerobiosis based on gas diffusion and microbial respirati on is proposed for soil aggregates. Unlike previous models, it account s 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 distribu tion within spherical remoulded aggregates of different sizes saturate d with water. Most of the model parameters were estimated experimental ly. Fick's law could describe O-2 diffusion inside the saturated aggre gates. The model agreed well with O-2 profiles measured soon after sat uration. Later, the model underestimated anaerobiosis, probably becaus e of changes in radial distribution of microbial activity inside the a ggregates. Respiration as a function of O-2 concentration was satisfac torily described by the model. Nevertheless, each size of aggregate wa s analysed separately because of an apparent relation between size and maximal aerobic respiration. This seems to be associated with a non-h omogeneous distribution of aerobic respiration. The model represents a n improvement on those currently used to estimate anaerobiosis inside aggregates.