An in situ method for remediating 137Cs-contaminated wetlands using naturally occurring minerals

Cesium's enhanced bioavailability in contaminated wetlands onthe U.S. Department of Energy's Savannah River Site (SRS) is thoughtto be due to the low clay fraction of SRS soils, and that the clay mineralogyis dominated by kaolinites. Remediation of the wetlands is problematic becausecurrent technologies are destructive to the sensitive ecosystems. We tested11 clay minerals (two micas, a vermiculite, six illites, a kaolinite, anda smectite) for their propensity to sorb and retain ¹³⁷Cs. Twominerals were subsequently chosen as candidates for in situ remediation amendmentmaterials because they had ¹³⁷Cs distribution coefficients (K d) well in excess of 10,000 ml . g –1 , and desorbed less than 20% ofthe Cs when mixed in a 0.1M NH 4 Cl solution. Incremental additions of thecandidate minerals to ¹³⁷Cs-contaminated sediments appreciablyintercepted and retained desorbed ¹³⁷Cs in the presence of highlevels of NH₄ . Implications for using the minerals as a nondestructive,in situ remediation technique are discussed.