sium-137 and other contaminants have leaked from many of the single-shell storage tanks at the Hanford Site in southeastern Washington. The leakage was into sandy unconsolidated sediments consisting largely of quartz, plagioclase, micas, smectite, and kaolinite. The contaminated sediments were sieved to investigate the distribution of Cs across the different sediment fractions. Characterization using X-ray diffraction showed the presence at all size fractions of mica, quartz, plagioclase, and smectite, 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 Cs. The Cs bearing particles were found to be either individual mica flakes or agglomerated smectite, mica, quartz, and plagioclase. Of these, only the micaceous component was capable of binding Cs irreversibly. Cs could not be significantly removed from sediments by leaching with dithionite citrate buffer or KOH, and a fraction of the Cs was cation desorbable with solutions containing an excess of Rb+. The small amount of 137Cs that could be mobilized by migrating fluids would likely sorb to nearby mica clasts in downgradient sediments.
Citation: Environmental Science & Technology
Issue: No. 17
Pub Type: Journals
autoradiography, cesium-137 fixation, clays clay minerals, environmental radioactivity, micaceous sediment leaching, phosphor imaging plates PSL, soil contamination, sorption desorption, x-ray diffraction XRD