Integrated modelling of eutrophication and organic contaminant fate in rivers

Eutrophication and contamination by toxic organic pollutants are the major problems in water quality management. Despite the fact that both problems have been subjected to extensive research and modelling, they have traditionally been treated separately. Because the models used are single-issue models, many interactions between nutrient cycles and organic contaminant fate and effect are missed. Linking these models is essential to evaluate the fate and risk of contaminants in aquatic ecosystems subjected to dynamic nutrient and organic contaminant loadings. Using a multi-compartment model (air, water and benthic sediment), and a conceptual dynamic hydraulic model (continuously stirred tank in series), a one-dimensional dynamic integrated model with basic water quality and organic contaminant fate sub-models is developed in this work. The model was evaluated based on the Crocodile River (South Africa) and the river Lambro (Italy) case studies for nutrient dynamics (inorganic nitrogen) and organic contaminant fate (Linear Alkylbenzene Sulfonates, LAS) respectively. The model calibration, validation and the scenario analysis results are presented. The results show that the interaction of nutrient dynamics and contaminant fate and effect should be considered in the exposure assessment of river ecosystem. Furthermore, the integrated model gives more valuable information for various scenario analyses than single-issue models.