Laboratory measurements of the strontium distribution coefficient KdSr for Sediments From a Shallow Sand Aquifer

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Abstract
A batch method has been modified and improved for measuring strontium distribution coefficients KdSr for sediments from the shallow aquifer at Chalk River. An average measured KdSr value of 10 ml/g for whole aquifer sediments compares favorably both with a field value of 7 ml/g determined using the retardation equation and with an average KdSr of 10 ml/g based on analytical results for aquifer sediments and coexisting groundwaters from a portion of the flow system that is contaminated with 90Sr. Measurements of KdSr for mineralogically pure segregates indicate that vermiculite, an alteration product of biotite, is the most effective adsorbent phase. KdSr results for grain size fractions suggest that the distribution of minerals with respect to grain size may strongly influence the KdSr of the whole sediment. Relationships between KdSr and exchangeable calcium on the sediments and competing cation concentration in the test solution indicate that electrostatic forces primarily control the sorption of strontium.