Comparison of multimedia model predictions for a contaminant plume migration scenario

Predictions of four risk assessment models - RESRAD, PRESTO, MMSOILS, and M EPAS for a test scenario involving the migration of a single, rapidly trans forming radionuclide, Sr-90, and a persistent, long radionuclide chain, U-2 34 and its progeny, in groundwater are compared. All four models make compa rable predictions for the plume centerline concentrations of the primary co ntaminants in the aquifer for a distance of up to about 300 m from the sour ce. MEPAS, MMSOILS, and RESRAD make similar predictions for the transverse concentration profiles in the aquifer. The four models make considerably di fferent predictions for the temporal concentration profiles of the progeny in the aquifer. The profiles differ in shape, magnitude of the peak, and in width. The differences are a result of the simplifying assumptions underly ing each of the models. (C) 2000 Elsevier Science B.V. All rights reserved.