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(124) Uncertainty analysis of multimedia model for evaluating the joint persistence of parent compounds and transformation products. Fenner, Kathrin1, Scheringer, Martin1, Hungerbuehler, Konrad1, 1 ABSTRACT- Many chemicals released to the environment are not completely and instantaneously mineralized but are transformed to structurally related compounds, all of them possessing a certain persistence in the environment. Previous approaches to calculate the persistence of organic chemicals with the help of multimedia fate models have not included transformation products. For this reason, we have developed a concept and the associated mathematical models to calculate the persistence of parent compounds and transformation products in combination (1). This inclusion of transformation products introduces significant additional uncertainties into the models. These comprise model uncertainty regarding the transformation pathways of the parent compound in the different environmental compartments, as well as additional parameter uncertainty and variability introduced through the physico-chemical properties of the transformation products and through their transformation rate constants. In order to evaluate the uncertainty we have applied the concept of joint persistence to three examples of chemicals, namely the degradation of perchloroethylene released to air, the degradation of atrazine released to soil and the degradation of nonylphenol ethoxylates released to surface water. The examples have been selected because of their divers environmental behavior and the reasonably good data situation. These case studies are used to analyze which uncertain factors contribute most to the uncertainty of the model output, i.e. the joint persistence values. Based on the results from the three examples recommendations are made regarding the application of the concept to other substance families, and conclusions are drawn regarding the possibility to simplify the mathematical model and to reduce the amount of input data needed. (1) Fenner, K.; Scheringer, M.; Hungerbuehler, K. Environ. Sci. Technol. 2000, 34, 1842-1850. Key words: transformation products, persistence, model uncertainty |
