Technetium reduction and reoxidation behaviour in Dounreay soils.

摘要: Summary. Technetium is a radioactive contaminant found in groundwaters at sites where nuclear wastes have been processed or stored. The redox chemistry of technetium major control on its environmental mobility. Under oxic conditions, exists as the pertechnetate ion, Tc(VII)O4 − ,w hich poorly sorbed by minerals across wide range environmentally relevant pH values. reducing conditions converted to lower valency species, which Tc(IV) tends predominate. Typically, oxidation state readily precipitates insoluble hydrous oxides or, low concentrations, removed from solution association with mineral surfaces. Here, we present novel X-ray absorption spectroscopy (XAS) data examining Tc associations reduced Dounreay soils. In unamended microcosms and added co-contaminants ethylenediaminetetraacetic acid (EDTA) bicarbonate investigate their effect biogeochemistry, was exposure sediments solids Tc(IV)O2-like phases. Furthermore, long term stability remobilization solid phase associated soils, reoxidized reduced, Tc(IV)-labeled presence air nitrate. extent dependent oxidant used. After reoxidation for 60 d, 42 ± 6% initial soil bound resolubilized. 25 100 mmol L −1 nitrate an oxidant, negligible microcosm occurred. XAS analysis soils treated two oxidants showed that both systems, remaining TcO2like recalcitrance under reoxidizing has implications fate contaminated environments.