Modelling diffusion and microbial uptake of ¹³C-glucose in soil aggregates

A deterministic model was developed to simulate the microbial utilization and diffusion of finite amounts of substrate from the surface of a model aggregate into the intra-aggregate pore spaces. Experiments were performed for comparison with the simulation results and to estimate the effective intra-aggregate diffusion coefficient for glucose. Glucose was applied to the surfaces of sterilized and nonsterilized aggregates and the induced ¹³CO₂-respiration and radial glucose distribution were measured. ATP measurements show a developing radial gradient of microbial activity decreasing from the outer to the inner part of the aggregate.