文摘
The chemical and biogeochemical reduction of pertechnetate(TcO4-) and perrhenate (ReO4-) have been comparedalongside complexation of the reduced species by threeanthropogenic 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 separatethe species and quantify Tc and Re. During methoddevelopment, ReO4- showed recalcitrance to direct chemicalreduction by Sn(II) under conditions that readily reducedTcO4- and resulted in Tc(IV)-organic complexes. Inmicrocosm experiments of a silty loam soil containingTcO4-, ReO4-, and ISA (3.0 mM), EDTA (0.17 mM), or NTA(2.4 mM), anoxia developed to iron-reducing conditionsduring the 42 day experimental period. The majority of theTcO4- was reduced to particle-reactive Tc(IV) andremoved from solution during nitrate reduction, but therewas no chromatographic evidence of Tc(IV)-organiccomplexes in the porewater. Overall, the excess organiccomplexants added did not cause a measurable differencein the solubility of Tc(IV) over the control experiments inthis organic-rich (12% organic carbon) soil. ReO4- did notundergo reduction, as shown by the constant porewaterconcentration and the chromatographic data, and thus Redoes not function as an analogue for Tc under environmentalnitrate- and iron-reducing conditions.