Geo-referenced Regional Exposure Assessment Tool for European Rivers (great-er): a Case Study for the Rupel Basin (b)

In the GREAT-ER project (Geography-referenced Regional Exposure Assessment Tool for European Rivers), an accurate aquatic exposure prediction tool for chemicals was developed and validated for use within environmental risk assessment schemes. In this paper, the application of the GREAT-ER methodology to the Rupel basin in Belgium is presented. Spatial concentration patterns of the anionic surfactant Linear Alkylbenzene Sulphonate (LAS) were predicted for this basin. Different scenarios were simulated. LAS removal in waste water treatment plants is high (98-99.9%). However, since only 30-40 % of the wastewater in the Rupel basin is treated, predicted environmental concentrations (PECs) are high. For some subbasins, calculated PEC-values were positioned against biological and physico-chemical water quality measurements. This case study showed the feasibility of implementing a new large catchment on a short term and indicated which efforts are required to apply GREAT-ER on a large, ultimately pan-European scale. It was found that it is possible to simplify the river network without considerable loss of accuracy. This allows to gain time and reduce effort. INTRODUCTION The goal of comprehensive risk assessment is to estimate the likelihood and the extent of adverse effects occurring to man, animals or ecological systems due to possible exposure(s) to substances. The assessment of whether a substance presents a risk to organisms in the environment is based on the comparison of a predicted environmental concentration (PEC) with a predicted no effect concentration (PNEC) to ecosystems (Feijtel et al., 1997). As the current generic ‘unit world’ techniques to assess regional exposure do not account for spatial and temporal variability and do not offer realistic predictions of actual concentrations, they are merely applicable on a screening level. The objective of the GREAT-ER project (Geographyreferenced Regional Exposure Assessment Tool for European Rivers) was to develop an accurate tool to predict chemical exposure in the aquatic environment (Feijtel et al., 1997). In GREAT-ER, a new database, model and software system were worked out to calculate the distribution of PEC’s of 'down-the-drain' chemicals in European surface waters, on a river and catchment area scale. The system uses a Geographic Information System (GIS) for data storage and visualisation, combined with simple mathematical models for the prediction of chemical fate. At present, the system contains information for four catchments in Yorkshire (UK), one in Italy, and two in Germany. GREAT-ER 1.0 has been validated by comparing simulations with the results of an extensive monitoring campaign for the detergent ingredients Linear Alkylbenzene Sulphonate (LAS) and boron (Feijtel et al., 1997; Schowanek et al., in press).