Behavior of 137Cs in ponds in the vicinity of the Fukushima Dai-ichi nuclear power plant

Temporal trends of <sup>137</sup>Cs activity concentration in pond waters in the vicinity of Fukushima Dai-ichi nuclear power plant

“…Although they suggested seasonal variation of dissolved 137 Cs activity concentration of water, long-term trends remained unclear due to short period of their observations. This study shows longer temporal trends of 137 Cs activity concentration in pond waters, as a continuation of observations undertaken by Wakiyama et al (2017). In addition, we evaluated contamination of bottom sediment and its speciation.…”

“…4). As indicated by Wakiyama et al (2017), the mean 137 Cs inventory in the soil around SU, FS, IZ and KM were 6.8, 4.6, 2.9 and 0.42 MBq m −2 , respectively. Similarly, mean 137 Cs inventory in bottom sediment in SU, FS, IZ and KM were 13, 8.9, 1.6 and 1.1 MBq m −2 , respec- tively.…”

“…We investigated the behaviour of 137 Cs in four small ponds around Fukushima Dai-ichi nuclear power plant as a following-up of observation by Wakiyama et al (2017). Continuous monitoring of 137 Cs activity concentration in water confirmed the presence of a seasonal cycle of dissolved 137 Cs activity concentration and newly revealed tendencies to a decrease trends in 137 Cs activity concentration in suspended sediment for all ponds.…”

“…1). The surface area of these ponds of SU, FS, IZ and KM was 4100, 10 700, 6500 and 8100 m 2 , respectively, and ambient dose equivalent rates measured on March 2014 around SU, FS, IZ and KM were 24, 6.0, 11 and 3.3 µSv h −1 , respectively (Wakiyama et al, 2017). The average annual precipitation and the average annual air temperature in this region were 1493 mm and 12.3 • C, respectively, according to Namie weather station data from 1976 to 2015.…”

“…However, the meteorological and geographical conditions in these areas are different from those in the Fukushima area, and the applicability of these results requires verification (Konoplev et al, 2016). Wakiyama et al (2017) demonstrated radiological contaminations in four ponds in the vicinity of FDNPP based on one-year observation. Although they suggested seasonal variation of dissolved 137 Cs activity concentration of water, long-term trends remained unclear due to short period of their observations.…”