Comparing estimates of persistence and long-range transport potential among multimedia models.

Overall persistence (Pov) and long-range transport potential (LRTP) of organic chemicals are environmental hazard metrics calculated with multimedia fate and transport models. Since there are several models of this type, it is important to know whether and how different model designs (model geometry, selection of compartments and processes, process descriptions) affect the results for Pov and LRTP. Using a set of 3175 hypothetical chemicals covering a broad range of partition coefficients and degradation half-lives, we systematically analyze the Pov and LRTP results obtained with nine multimedia models. We have developed several methods that make it possible to visualize the model results efficiently and to relate differences in model results to mechanistic differences between models. Rankings of the hypothetical chemicals according to Pov and LRTP are highly correlated among models and are largely determined by the chemical properties. Domains of chemical properties in which model differences lead to different results are identified, and guidance on model selection is provided for model users.