Chemical implication of partition coefficients between suspended/sediment and dissolved Cs-137 in natural water

Abstract

To better understand the partition coefficient, Kd, of Fukushima-derived radiocesium in natural water, we determined Kd of ¹³⁷Cs between water and suspended matter in rivers in Fukushima Prefecture. The Kd values, ranged from 22000 to 7000000 L/kg, showed large variability and were greater than that between seawater and sediment. For Yugama crater of Kusatsu-Shirane volcano, low Kd value (20 +/-19 L/kg) was determined between water and sediment collected in Yugama. Examination of chemical factors controlling the partition coefficient of ¹³⁷Cs revealed that the Kd values are closely related to ¹³³Cs (stable isotope) concentrations in natural water, which implies that isotope exchange reaction between ¹³⁷Cs and ¹³³Cs is one of the important chemical processes.