PARENT SESSION
MA8a Addressing the Uncertainty of ERA.
9:00 AM to 11:00 AM, Monday, 07 May 2001
Session Chair: R. Ribeiro
Room 8

(067) Probabilistic uncertainty analysis for EUSES multimedia regional distribution model.

Matthies, Michael¹, Berding, Volker ¹, ¹

ABSTRACT- In the European Union chemical legislation, both new notified and existing substances are subject to environmental risk assessment. For the calculation of the regional background concentration, proposed in the Technical Guidance Documents (TGD) and implemented in the European Union System for the Evaluation of Substances (EUSES), a multimedia distribution model is used. It is a mass balance model of the Level 3 type and consists of the environmental media air, surface water, sediment and three soil compartments (natural, agricultural and urban/industrial), which are connected by intermedia mass transfer processes. Any chemical emitted in one or more compartments can be subjected by intramedia transformation or advective loss processes. The model output are "Predicted Environmental Concentrations (PEC_regional)" for all compartments. To determine the influence of the uncertainty and variability of the input parameters on the PEC_regional, a sensitivity and uncertainty analysis was carried out by using regional and emission data from North-Rhine Westphalia (NRW) in Germany. Three scenarios were set up: variation of only the substance parameters, variation of only the regional parameters and variation of all input parameters at the same time. These three scenarios were calculated for each of the considered substances benzene, DEHP, EDC, EDTA, HHCB, LAS, and seven PCDD-isomers. Concentrations in air have the lowest average uncertainty due to variation of all parameters, followed by concentrations in water and sediment. Concentrations in soil distinctly have the highest uncertainties. In most cases, the contribution of the regional parameters to the total uncertainties is higher than that of the substance parameters. For water, sediment and soil the uncertainties due to variations of the substance parameters are lower than due to variations in the regional parameters; for air they are higher. The highest occurring range is 1.8 orders of magnitude, which means that the total uncertainty of the regional model is relatively low and usually lower than the range of measured values taken from monitoring programmes in NRW.

Key words: EUSES, multimedia exposure model, probabilistic assessment, uncertainty analyis