CATS-2: een model ter voorspelling van accumulatie van microverontreinigingen in sedimentatiegebieden van rivieren

Abstract

CATS is an acronym for Contaminants in Aquatic and Terrestrial ecoSystems. CATS models have been developed for the prediction of fate and risks of toxicants. The aim of these models is to predict future risk levels of toxic substances for food webs. CATS-2 describes the behaviour of toxicants in sedimentation areas of main rivers in the Netherlands, such as Hollands Diep, Haringvliet and Ketelmeer. Bio-availability of toxicants to aquatic organisms is influenced by many biotic and abiotic characteristics of an ecosystem. Therefore, we integrated fate of toxicants in the abiotic environment with a food web model based on biomass cycling. Cycling of organic matter is the backbone of the model, acting as carrier for the toxicant. The food web consists of algae, zooplankton, bivalves, chironomid larvae, tubificid worms, whitefish, predatory fish, benthivorous fish, diving ducks and fish eating birds (Fig. 1). Cadmium and lindane (gamma-HCH) were selected to predict future risk levels in an example ecosystem, the Hollands Diep/Haringvliet area. Risk levels were calculated for two situations. First for the year 2000, with no additional clean-up of the river Rhine, and second for the year 2000 with additional clean-up according to the Rhine Action Programme. Model calculations predict that risks for both cadmium and lindane decrease, caused by the improvement of water quality in the River Rhine that feeds the area. The high cadmium load of the river Rhine in the past is responsible for high cadmium concentrations in the sediment. Even with additional clean up, sediment quality does not meet the Dutch quality objective of 2 mg/kg d.w. in the year 2000. Except for benthivorous fish, risks for the food web are low in the year 2000 indicating that in general the Rhine Action Plan is successful if its original emission-reduction goals can be achieved.