TY - JOUR
T1 - Cryogenic laser induced fluorescence characterization of U(VI) in Hanford vadose zone pore waters
AU - Wang, Zheming
AU - Zachara, John M.
AU - Yantasee, Wassana
AU - Gassman, Paul L.
AU - Liu, Chongxuan
AU - Joly, Alan G.
PY - 2004/11/1
Y1 - 2004/11/1
N2 - Ambient and liquid helium temperature laser-induced time-resolved uranyl fluorescence spectroscopy was applied to study the speciation of aqueous uranyl solutions containing carbonate and phosphate and two porewater samples obtained by ultracentrifugation of U(VI)-contaminated sediments. The significantly enhanced fluorescence signal intensity and spectral resolution found at liquid helium temperature allowed, for the first time, direct fluorescence spectroscopic observation of the higher aqueous uranyl complexes with carbonate: UO2(CO3)22-, UO2(CO 3)34-, and (UO2)2(OH) 3CO3-. The porewater samples were nonfluorescent at room temperature. However, at liquid helium temperature, both porewater samples displayed strong, well-resolved fluorescence spectra. Comparisons of the spectroscopic characteristics of the porewaters with those of the standard uranyl-carbonate complexes confirmed that U(VI) in the porewaters existed primarily as UO2(CO3)34- along with a small amount of other minor components, such as dicalcium-urano-tricarbonate complex, Ca2UO2(CO 3)3, consistent with thermodynamic calculation. The U(VI)-carbonate complex is apparently the mobile species responsible for the subsurface migration of U(VI), even though the majority of the in-ground U(VI) inventory at the site from which the samples were obtained exists as intragrain U(VI)-silicate precipitates.
AB - Ambient and liquid helium temperature laser-induced time-resolved uranyl fluorescence spectroscopy was applied to study the speciation of aqueous uranyl solutions containing carbonate and phosphate and two porewater samples obtained by ultracentrifugation of U(VI)-contaminated sediments. The significantly enhanced fluorescence signal intensity and spectral resolution found at liquid helium temperature allowed, for the first time, direct fluorescence spectroscopic observation of the higher aqueous uranyl complexes with carbonate: UO2(CO3)22-, UO2(CO 3)34-, and (UO2)2(OH) 3CO3-. The porewater samples were nonfluorescent at room temperature. However, at liquid helium temperature, both porewater samples displayed strong, well-resolved fluorescence spectra. Comparisons of the spectroscopic characteristics of the porewaters with those of the standard uranyl-carbonate complexes confirmed that U(VI) in the porewaters existed primarily as UO2(CO3)34- along with a small amount of other minor components, such as dicalcium-urano-tricarbonate complex, Ca2UO2(CO 3)3, consistent with thermodynamic calculation. The U(VI)-carbonate complex is apparently the mobile species responsible for the subsurface migration of U(VI), even though the majority of the in-ground U(VI) inventory at the site from which the samples were obtained exists as intragrain U(VI)-silicate precipitates.
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U2 - 10.1021/es049512u
DO - 10.1021/es049512u
M3 - Article
C2 - 15575276
AN - SCOPUS:7544222387
SN - 0013-936X
VL - 38
SP - 5591
EP - 5597
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 21
ER -