文摘
The highest stream water dissolved 137Cs concentration recorded at Iboishi-yama was 1.2 Bq/L on August 6, 2011. During the rainfall events, the concentration of dissolved 137Cs concentration in stream water increased temporarily. The dissolved 137Cs concentration in groundwater at a depth of 30 m at Iboishi-yama ranged 0.0025–0.039 Bq/L. The effective half-lives of stream water in the initial fast flush and secondary phases were 0.10–0.21 and 0.69–1.5 y. The effective half-lives of groundwater was 0.46–0.58 y at Koutaishi-yama and 0.50–3.3 y at Iboishi-yama.