title: Effect of organic co-contaminants on technetium and rhenium speciation and solubility under reducing conditions.
abstract: The chemical and biogeochemical reduction of pertechnetate (TcO4-) and perrhenate (ReO4-) have been compared alongside complexation of the reduced species by three anthropogenic ligands relevant to nuclear waste (ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and isosaccharinic acid (ISA)). An HPLC size-exclusion column coupled to ICP-MS was used to separate the species and quantify Tc and Re. During method development, ReO4- showed recalcitrance to direct chemical reduction by Sn(ll) under conditions that readily reduced TcO4- and resulted in Tc(IV)-organic complexes. In microcosm experiments of a silty loam soil containing Tc04-, ReO4-, and ISA (3.0 mM), EDTA (0.17 mM), or NTA (2.4 mM), anoxia developed to iron-reducing conditions during the 42 day experimental period. The majority of the TcO4- was reduced to particle-reactive Tc(IV) and removed from solution during nitrate reduction, but there was no chromatographic evidence of Tc(IV)-organic complexes in the porewater. Overall, the excess organic complexants added did not cause a measurable difference in the solubility of Tc(IV) over the control experiments in this organic-rich (12% organic carbon) soil. ReO4- did not undergo reduction, as shown by the constant porewater concentration and the chromatographic data, and thus Re does notfunction as an analogue forTc under environmental nitrate- and iron-reducing conditions.
authors.affiliation: School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.
authors.forename: Estela Reinoso
authors.initials: ER
authors.lastname: Maset
authors.forename: Stephanie H
authors.initials: SH
authors.lastname: Sidhu
authors.forename: Andrew
authors.initials: A
authors.lastname: Fisher
authors.forename: Andrew
authors.initials: A
authors.lastname: Heydon
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Worsfold
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Cartwright
authors.forename: Miranda J
authors.initials: MJ
authors.lastname: Keith-Roach
mesh_terms: D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D013058:Mass Spectrometry; D009930:Organic Chemicals / Q000737:chemistry*; D010084:Oxidation-Reduction; D012211:Rhenium / Q000737:chemistry*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis*; D012995:Solubility; D013667:Technetium / Q000737:chemistry*
chemical_list: D009930:Organic Chemicals; D012989:Soil Pollutants; D012211:Rhenium; D013667:Technetium