Comparison of a simple and a complex sediment phosphorus model

Abstract

A model describing phosphorus and oxygen conditions in lake sediments is presented as a set of partial differential equations. The mechanisms included are anaerobic and aerobic decomposition, diffusion, adsorption, chemosorption, sedimentation and resuspension. The decomposition process takes into account that effective age profiles are influenced by oxygen and temperature conditions. The driving variables and comparisons with measurements are based on experimental data from Lake Esrom. The results are compared with those obtained using a simpler model (previously published) and it is found that the more complex model does not fit the observed values better than does the simpler model unless an additional process—grazing at the sediment surface—is incorporated. However, it has been possible to use the complex model to relate the empirical parameters in the simpler model to generally applied concepts such as diffusion coefficients, the thickness of the transition layer, the sediment compaction and the annual net sedimentation.