An investigation of groundwater organics, soil minerals, and activated carbon on the complexation, adsorption, and separation of technetium-99

Evaluation of natural attenuation processes for trichloroethylene and technetium-99 in the Northeast and Northwest plumes at the Paducah Gaseous Diffusion Plant, Paducah, Kentucky

“…l%ebmdthof theverticalvariations in Eh is indicative of the lack of redox equilibrium. In any case, the redox conditions in general support the work of Gu et al (1994) and Gu and Dowlen (1996) which found %fc is not transported as a colloidal particle, sorbed or complexed with mtural organic matter in groundwatcr, or sorbed onto the aqtier matrix. Furthermore, the presence of 9Tc off-site to a distance of 3.1 ' miles tim the sourceis suggestive of a non-reactive solute.…”

“…Additionally, WC is present off-site as far as 3.1 miles from the source area within the Northwest Plume indicating~c is in a very mobile state. This was confirmed by the work of Gu and Dowlen (1996) which found no measumblesorption of~c onto RGA lithologic material. Thus, there is little evidence for the reduction of ?I'c levelsthrough precipitationor sorption The long radioactive decay process for 'Tc, as discussed in Section 1.6,precludesthis mechanism as an important means for the reduction of 'Tc.…”

“…Thus, all of the data cdlectcd to date is suggestive that TcO( is the form OP Tc present at the PGDP site. Given the nature of Tc(3 and the work of Gu and Dowlen (1996) WC is not expected to be retarded to any significant degree by the sediments at PGDP. Gu and Dowlen (1996) show WC behaves essentially as an unreactive tracer at PGDP.…”

“…The role of sorption of~c at PGDP was evaluated by Gu and Dowlen (1996) who found no measurable evidence for the sorption or precipitation of 'Tc onto RGA sediments. Thus, the measured partitioning coetlkcient(IQ for~c was less than 0.01, whichyields a retardation factor of 1.0, i.e.…”

Use of Apatite for Chemical Stabilization of Subsurface Contaminants

“…Results, summarized in Table 28, indicate that apatite products have relatively modest affinity for pertechnetate ion, compared to the acid-washed coal. In low-ionic strength solution, the pertechnetate ion readily binds to various forms of activated carbon (Gu and Dowlen, 1996); the Waterlink® animal bone char contains a residual of ~ 10.8 wt% activated carbon, which likely imparts some affinity for the pertechnetate ion, relative to raw or oxidized fish bone.…”