Dynamic Modelling of Phosphorus Release from Sediments

The analysis of nutrient release from sediments in shallow eutrophic lakes is an important stage in properly describing such ecological systems. (On the subject of lake ecosystem modelling, consult, for instance, Park et al., 1974; Scavia, 1980; Orlob, 1983; Somlyódy and van Straten, 1986; Riley and Stefan, 1988; and also Chapters 4.6 and 4.11.) SED is a dynamic model that was developed (and tested on Lake Veluwe, Netherlands data) for describing the release of phosphorus from lake sediments (Van der Molen, 1991). The model includes three environmental state variables: dissolved phosphorus, organic particulate sediment phosphorus, and active sediment layer. It considers only the basic relationships between these variables. Specifically, processes of the diffusive transport of dissolved phosphorus to the overlying water body, mineralization of organic phosphorus in the sediment, and adsorption/desorption and fixation of inorganic phosphorus are modelled by SED. To describe this model, the following notation is introduced: