Na. Marley et al., EVIDENCE FOR RADIONUCLIDE TRANSPORT AND MOBILIZATION IN A SHALLOW, SANDY AQUIFER, Environmental science & technology, 27(12), 1993, pp. 2456-2461
Evidence is reported for the movement of plutonium, americium, thorium
, and radium in a shallow, sandy aquifer after the forced injection of
colloidal and macromolecular natural organic materials (humic and ful
vic acids). Ultrafiltration was used to size-fractionate the materials
smaller than 0.45 mum in the injection water. Characterization of the
se organic materials showed the most mobile to be primarily fulvic aci
ds with a high carboxylate content. Fallout-derived plutonium and amer
icium in the injected materials were transported in the aquifer with t
he smaller organic fractions. Americium was shown to move from the les
s mobile colloidal materials to the smaller more mobile fulvics during
transport. Thorium, uranium, and radium levels all increased upon inj
ection of the organics into the aquifer, demonstrating the ability of
low molecular weight, high carboxylic content fulvic acids to dissolve
and mobilize radionuclides from the aquifer's mineral matrices. This
effect also increased with decreasing flow rate in the aquifer. The im
plications of these observations for the interactions of low-level rad
ioactive waste with natural organics are discussed.