Distribution and Retention of 137Cs in Sediments at the Hanford Site, Washington

Authors

• James Mckinley, Pacific Northwest National LaboratoryFollow
• Cynthia Zeissler, National Institute for Standards and Technology
• John M. Zachara, Pacific Northwest National LaboratoryFollow
• R. Jeffrey Serne, Pacific Northwest National Laboratory
• Richard Lindstrom, National Institute for Standards and Technology
• Herbert Schaef, Pacific Northwest National Laboratory
• Robert Orr, Pacific Northwest National Laboratory

Date of this Version

2001

Citation

Environ. Sci. Technol. 2001, 35, 3433-3441

Abstract

¹³⁷Cesium and other contaminants have leaked from single-shell storage tanks (SSTs) into coarse-textured, relatively unweathered unconsolidated sediments. Contaminated sediments were retrieved from beneath a leaky SST to investigate the distribution of adsorbed ¹³⁷Cs⁺ across different sediment size fractions. All fractions contained mica (biotite, muscovite, vermiculatized biotite), quartz, and plagioclase along with smectite and kaolinite in the clay-size fraction. A phosphor-plate autoradiograph method was used to identify particular sediment particles responsible for retaining ¹³⁷Cs⁺. The Cs-bearing particles were found to be individual mica flakes or agglomerated smectite, mica, quartz, and plagioclase. Of these, only the micaceous component was capable of sorbing Cs⁺ strongly. Sorbed ¹³⁷Cs⁺ could not be significantly removed from sediments by leaching with dithionite citrate buffer or KOH, but a fraction of the sorbed ¹³⁷Cs⁺ (5-22%) was desorbable with solutions containing an excess of Rb⁺. The small amount of ¹³⁷Cs⁺ that might be mobilized by migrating fluids in the future would likely sorb to nearby micaceous clasts in downgradient sediments.