Chemical and physical properties affecting strontium distribution coefficients of surficial-sediment samples at the Idaho National Engineering and Environmental Laboratory, Idaho

The U.S. Geological Survey and Idaho University, in cooperation with the U. S. Department of Energy, conducted a study to determine strontium distribut ion coefficients (K(d)s) Of surficial sediments at the Idaho National Engin eering and Environmental Laboratory (INEEL). Batch experiments using synthe sized aqueous solutions used to determine K(d)s, which describe the distrib ution of a solute between the solution and phase, of 20 surficial-sediment samples from NEEL. The KdS for the 20 surficial-sediment les ranged from 36 to 275 ml/g. Many properties of both the synthesized aqueous solutions and tents used in the experiments also were determined. Solution properties de termined were initial equilibrium concentrations of calcium, magnesium and strontium, pH and specific conductance, and initial concentrations of potas sium and sodium. Sediment properties determined were grain-size distributio n, bulk mineralogy, whole-rock major-oxide and strontium and barium concent rations, and Brunauer-Emmett-Teller (BET) surface Solution and sediment pro perties were correlated with strontium K(d)s of the 20 surficial sedis usin g Pearson correlation coefficients, Solutions properties with the strongest correlations with strontium KdS were equilibrium pH and equilin calcium co ncentration correlation coefficients, 0.6598 and -0.6518, respectively. Sed iment properties with the strongest correlations with strontium K(d)s were manganese oxide (MnO), BET area, and the >4.75-mm-grain-size fraction corre lation coefficients, 0.7054, 0.7022, and -0.6660, respectively. Effects of solution properties on strontium KdS were interpreted as being due to compe tition among similarly charged and sized cations in solution for strontium- sorption sites; effects of sediment properties on strontium KdS were interp reted as being surface-area related. Multivariate analyses of these solutio n and sediment properties resulted in r(2) values of 0.8071 when all five p roperties were used and 0.8043 when three properties, equilibrium pH, MnO, and BET surface area, were used.