MODELING SOLUTE LEACHING IN SOILS BY DIFFUSION-LIMITED AGGREGATION - BASIC CONCEPTS AND APPLICATION TO CONSERVATIVE SOLUTES

The diffusion-limited aggregation (DLA) model introduced by Witten and Sander (1981) was modified to describe leaching of conservative solut es through soils. In the DLA concept, particles that move by random wa lk (diffusion) form aggregates. This model was adapted by modifying th e walking probabilities and by introducing layers. The model does not describe the actual random walk of solutes in a heterogeneous flow fie ld, but it can describe results of observed experimental outcomes with a minimal set of parameters. The modified model is versatile: homogen eous distributions of chemicals can be simulated, such as those produc ed with piston flow on the one hand, and complicated distributions ari sing from macropore flow and fingering on the other hand. The model wa s successfully applied to the results of a held experiment where prefe rential flow of bromide occurred.