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 distribution coefficients (K(d)s) Of surficial sediments at the Idaho National Engineering and Environmental Laboratory (INEEL). Batch experiments using synthesized aqueous solutions used to determine K(d)s, which describe the distribution 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 determined were initial equilibrium concentrations of calcium, magnesium and strontium, pH and specific conductance, and initial concentrations of potassium and sodium. Sediment properties determined were grain-size distribution, bulk mineralogy, whole-rock major-oxide and strontium and barium concentrations, and Brunauer-Emmett-Teller (BET) surface Solution and sediment properties were correlated with strontium K(d)s of the 20 surficial sedis using Pearson correlation coefficients, Solutions properties with the strongest correlations with strontium KdS were equilibrium pH and equilin calcium concentration correlation coefficients, 0.6598 and -0.6518, respectively. Sediment properties with the strongest correlations with strontium K(d)s were manganese oxide (MnO), BET area, and the >4.75-mm-grain-size fraction correlation coefficients, 0.7054, 0.7022, and -0.6660, respectively. Effects of solution properties on strontium KdS were interpreted as being due to competition among similarly charged and sized cations in solution for strontium-sorption sites; effects of sediment properties on strontium KdS were interpreted as being surface-area related. Multivariate analyses of these solution and sediment properties resulted in r(2) values of 0.8071 when all five properties were used and 0.8043 when three properties, equilibrium pH, MnO, and BET surface area, were used.