Vertical migration of 134Cs bearing soil particles in arid soils: implications for plutonium redistribution

Abstract

Vertical migration of plutonium in soils at the Waste Isolation Pilot Plant (WIPP) and the Rocky Flats Environmental Technology Site (RFETS) was evaluated based on observed 134Cs migration in soil column experiments. After applying 134Cs-labeled soil particles to the surfaces of large, undisturbed soil cores collected from each site, resulting soil columns were subjected to experimental cycles of irrigation plus drying (treatment columns) or to cycles of irrigation only (control columns). Mean losses of 134Cs inventory from soil surfaces were 3.1 ± 0.6% cycle −1 and 0.7 ± 0.6% cycle −1 respectively for RFETS treatment and control columns. WIPP columns had mean respective losses of 1.3 ± 1.2% cycle −1 and 0.5 ± 0.2% cycle −1. Bulk transport of labeled soil particles through soil cracks was an important process in RFETS soils, accounting for 64–86% of total 134Cs migration. Colloidal transport processes governed migration in WIPP soils.