TY - JOUR

T1 - Speciation of uranium:

T2 - Compilation of a thermodynamic database and its experimental evaluation using different analytical techniques

AU - Mühr-Ebert, Elena L.

AU - Wagner, Frank

AU - Walther, Clemens

N1 - Funding information: Financial support for this research was provided by the Federal Institute for Geosciences and Natural Resources . We thank Wismut GmbH for providing natural analogues for groundwater and pore water chemistry from uranium mining legacy sites, which enabled this study to select appropriate synthetic water compositions. The authors would like to thank Vivien Schulte for providing us with Fig. 1 and editing Figs. 2 and 3 .

PY - 2019/1

Y1 - 2019/1

N2 - Environmental hazards are caused by uranium mining legacies and enhanced radioactivity in utilized groundwater and surface water resources. Knowledge of uranium speciation in these waters is essential for predicting radionuclide migration and for installing effective water purification technology. The validity of the thermodynamic data for the environmental media affected by uranium mining legacies is of utmost importance. Therefore, a comprehensive and consistent database was established according to current knowledge. The uranium data included in the database is based on the NEA TDB (Guillaumont et al., 2003) and is modified or supplemented as necessary e.g. for calcium and magnesium uranyl carbonates. The specific ion interaction theory (Brönsted, 1922) is used to estimate activity constants, which is sufficient for the considered low ionic strengths. The success of this approach was evaluated by comparative experimental investigations and model calculations (PHREEQC (Parkhurst and Appelo, 1999)) for several model systems. The waters differ in pH (2.7–9.8), uranium concentration (10−9-10−4 mol/L) and ionic strength (0.002–0.2 mol/L). We used chemical extraction experiments, ESI-Orbitrap-MS and time-resolved laser-induced fluorescence spectroscopy (TRLFS) to measure the uranium speciation. The latter method is nonintrusive and therefore does not change the chemical composition of the investigated waters. This is very important, because any change of the system under study may also change the speciation.

AB - Environmental hazards are caused by uranium mining legacies and enhanced radioactivity in utilized groundwater and surface water resources. Knowledge of uranium speciation in these waters is essential for predicting radionuclide migration and for installing effective water purification technology. The validity of the thermodynamic data for the environmental media affected by uranium mining legacies is of utmost importance. Therefore, a comprehensive and consistent database was established according to current knowledge. The uranium data included in the database is based on the NEA TDB (Guillaumont et al., 2003) and is modified or supplemented as necessary e.g. for calcium and magnesium uranyl carbonates. The specific ion interaction theory (Brönsted, 1922) is used to estimate activity constants, which is sufficient for the considered low ionic strengths. The success of this approach was evaluated by comparative experimental investigations and model calculations (PHREEQC (Parkhurst and Appelo, 1999)) for several model systems. The waters differ in pH (2.7–9.8), uranium concentration (10−9-10−4 mol/L) and ionic strength (0.002–0.2 mol/L). We used chemical extraction experiments, ESI-Orbitrap-MS and time-resolved laser-induced fluorescence spectroscopy (TRLFS) to measure the uranium speciation. The latter method is nonintrusive and therefore does not change the chemical composition of the investigated waters. This is very important, because any change of the system under study may also change the speciation.

UR - http://www.scopus.com/inward/record.url?scp=85057876107&partnerID=8YFLogxK

U2 - 10.1016/j.apgeochem.2018.10.006

DO - 10.1016/j.apgeochem.2018.10.006

M3 - Article

AN - SCOPUS:85057876107

VL - 100

SP - 213

EP - 222

JO - Applied Geochemistry

JF - Applied Geochemistry

SN - 0883-2927

ER -