1. Chemical implication of the partition coefficient of 137Cs between the suspended and dissolved phases in natural water.
- Author
-
Hirose, Katsumi, Onda, Yuichi, Tsukada, Hirofumi, Hiroyama, Yuko, Okada, Yukiko, and Kikawada, Yoshikazu
- Subjects
- *
NUCLEAR power plant accidents , *ISOTOPE exchange reactions , *CHEMICAL models , *ELECTRIC conductivity , *SUSPENDED sediments - Abstract
After the Fukushima Daiichi nuclear power plant accident, the terrestrial environment became severely contaminated with radiocesium. Consequently, the river and lake water in the Fukushima area exhibited high radiocesium levels, which declined subsequently. The partition coefficient of 137Cs between the suspended sediment (SS) and dissolved phases, K d , was introduced to better understand the dynamic behavior of 137Cs in different systems. However, the K d values in river water, ranging from 2 × 104 to 7 × 106 L kg−1, showed large spatiotemporal variability. Therefore, the factors controlling the 137Cs partition coefficient in natural water systems should be identified. Herein, we introduce a chemical model to explain the variability in 137Cs K d in natural water systems. The chemical model includes the complexation of Cs+ with mineral and organic binding sites in SS, metal exchange reactions, and the presence of colloidal species. The application of the chemical model to natural water systems revealed that Cs+ is strongly associated with binding sites in SS, and a major chemical interaction between 137Cs and the binding sites in SS is the isotope exchange reaction between stable Cs and 137Cs, rather than metal exchange reactions with other metal ions such as potassium ions. To explain the effect of the SS concentration on K d , the presence of colloidal 137Cs passing through a filter is significant as the dominant dissolved species of 137Cs in river water. These results suggest that a better understanding of stable Cs dissolved in natural water is important for discerning the geochemical and ecological behaviors of 137Cs in natural water. [Display omitted] • Partition coefficients of 137Cs between water and sediment are useful parameter to understand behaviors of 137Cs in environment. • Chemical model was applied to partitioning of 137Cs between natural water and suspended sediment. • Chemical model was based on concepts of isotope exchange equilibrium and mass balance including multi-reaction sites and colloidal forms. • Chemical model could confirm that the K d in fresh waters is inversely related to stable cesium (133Cs) concentrations. • 133Cs concentrations are one of the most important factors to control the K d in natural water systems. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF