5:15 PM - 7:15 PM
[MAG34-P02] Dynamics of 137 Cesium in water bodies of an urban area in Fukushima
Keywords:urban area, particulate normalized 137Cs concentration, stable isotope ratios
Fourteen years have passed since the accident at the Tokyo Electric Power Company's Fukushima Dai-ichi Nuclear Power Plant in March 2011. Rates of decrease in 137Cs concentrations in of suspended solids and dissolved fraction in urban rivers are reportedly faster than those in rivers of foresteds and agricultural catchments. On the other hand, high concentrations of 137Cs in concentrations in water and sediment in urban areas were also reported. Some authors explored urban-specific substances or environmental conditions for persistent contamination. However, there are still uncertainties of 137Cs dynamics in urban areas because of relatively small numbers of research focusing on urban areas.
This study targeted rivers, waterways, and reservoirs in and around central Koriyama City, mainly on the left bank of the Abukuma River. From August 2023 to August 2024, 40 L water samples were collected for 5 times under low-flow condition and 3 times under high-flow condition at 17 locations; 6 on a small-flow route that crosses the city center, 2 on the Ouse River without reservoir in its catchment, 3 on the Minami River with reservoirs in its catchment, 2 on the Abukuma River, and 4 on miscellaneous points within the city. The water samples were filtered to measure the 137Cs concentration of suspended solids (SS) (Bq/kg), particulate 137Cs concentration (Bq/L), and dissolved 137Cs concentration (Bq/L). In addition, stable isotope ratios, δ15N and δ13C (‰) and heavy metals (Cr, Cu, Fe, Mn, Pb, V) contents (ppm) were measured and subject to analyses of the factors influencing on the 137Cs concentration of SS.
The particulate 137Cs concentration was 0.0003-0.7 Bq/L, and the dissolved 137Cs concentration was 0.001-0.08 Bq/L. Among 5 sampling campaigns, particulate and dissolved 137Cs concentrations were highest in May 2024 and August 2024, respectively, and the lowest in December 2023 and August 2024, respectively. In the small-flow route, the 137Cs concentration of SS ranged from 0.7-6.9 kBq/kg and tended to increase toward downstream direction. On the other hand, there was no significant difference in the dissolved 137Cs concentration between upstream and downstream, suggesting that the inflow of the particulate 137Cs increased the 137Cs concentration. In the small-flow route collected SS samples showed a positive correlation between the normalized 137Cs concentration and δ15N. In addition, the normalized dissolved 137Cs concentrations were positively correlated. This result suggests that any anthropogenic substances may be a factor in increasing the 137Cs concentration. On the other hand, the normalized dissolved 137Cs concentrations were positively correlated with same ions such as Mg2+ and K+ and organic matters. This suggests that the source of SS may be of forest, as do δ13C results. Furthermore, that significantly and positively correlated with minor heavy metals such as Cu, Cr, Ni, Pb and Zn at the 1% level. These are also known tracers of road dust, and their relationship to forest origin will be the subject of further investigation.
This study targeted rivers, waterways, and reservoirs in and around central Koriyama City, mainly on the left bank of the Abukuma River. From August 2023 to August 2024, 40 L water samples were collected for 5 times under low-flow condition and 3 times under high-flow condition at 17 locations; 6 on a small-flow route that crosses the city center, 2 on the Ouse River without reservoir in its catchment, 3 on the Minami River with reservoirs in its catchment, 2 on the Abukuma River, and 4 on miscellaneous points within the city. The water samples were filtered to measure the 137Cs concentration of suspended solids (SS) (Bq/kg), particulate 137Cs concentration (Bq/L), and dissolved 137Cs concentration (Bq/L). In addition, stable isotope ratios, δ15N and δ13C (‰) and heavy metals (Cr, Cu, Fe, Mn, Pb, V) contents (ppm) were measured and subject to analyses of the factors influencing on the 137Cs concentration of SS.
The particulate 137Cs concentration was 0.0003-0.7 Bq/L, and the dissolved 137Cs concentration was 0.001-0.08 Bq/L. Among 5 sampling campaigns, particulate and dissolved 137Cs concentrations were highest in May 2024 and August 2024, respectively, and the lowest in December 2023 and August 2024, respectively. In the small-flow route, the 137Cs concentration of SS ranged from 0.7-6.9 kBq/kg and tended to increase toward downstream direction. On the other hand, there was no significant difference in the dissolved 137Cs concentration between upstream and downstream, suggesting that the inflow of the particulate 137Cs increased the 137Cs concentration. In the small-flow route collected SS samples showed a positive correlation between the normalized 137Cs concentration and δ15N. In addition, the normalized dissolved 137Cs concentrations were positively correlated. This result suggests that any anthropogenic substances may be a factor in increasing the 137Cs concentration. On the other hand, the normalized dissolved 137Cs concentrations were positively correlated with same ions such as Mg2+ and K+ and organic matters. This suggests that the source of SS may be of forest, as do δ13C results. Furthermore, that significantly and positively correlated with minor heavy metals such as Cu, Cr, Ni, Pb and Zn at the 1% level. These are also known tracers of road dust, and their relationship to forest origin will be the subject of further investigation.