Simulating reactive transport in sediments using a component additivity non-electrostatic surface complexation and ion exchange approach

GEOC 81

Mavrik Zavarin, zavarin1@llnl.gov, Chemistry and Materials Science, Seaborg Institute, Lawrence Livermore National Laboratory, L-231, Livermore, CA 94551
In 1989, Fletcher and Sposito published the fourth of a series of papers on the topic of clay/electrolyte interactions. They provided a self-consistent thermodynamic database for predicting the chemical properties of natural fluids and mineral assemblages. These data are now being incorporated into mechanistic reactive transport codes to simulate contaminant transport. Their data were combined with non-electrostatic surface complexation to iron oxide and calcite and ion exchange to mica and zeolite. The component additivity approach, in combination with mineral dissolution/precipitation reactions, was used to predict the release and transport of radioactive Ca, Ni, Sr, Cs, Sm, Eu, Np, Pu, and Am from Nevada Test Site underground nuclear tests. Given the mineralogic and hydrologic heterogeneity of the natural environment and the uncertainty of the various surface complexation/ion exchange parameters controlling sorption, the component additivity approach may be the most appropriate model for describing contaminant migration in natural environments.