Closed and semi-closed water bodies, such as lakes and
ponds, are important water resources in Fukushima area and they are the most
sensitive environments to radioactive contamination after the Fukushima
Dai-ichi nuclear power plant accident. Wakiyama et al. (2017) investigated
Closed and semi-closed water bodies, such as lakes and ponds, are the most sensitive environments to radionuclide contamination. More than 3700 individual irrigation ponds of different sizes are located in Fukushima Prefecture, which are radiologically contaminated after the Fukushima Dai-ichi nuclear power plant (FDNPP) accident. The Tohoku Regional Agricultural Administration Office of the Ministry of Agriculture, Forestry and Fishery (MAFF) and the Fukushima Prefectural government (MAFF and Fukushima prefecture, 2015) investigated 2679 ponds in Fukushima Prefecture and reported their water and sediment contamination levels.
The long-term behaviour of radiocesium in a closed and semi-enclosed water
system affected by the Chernobyl accident can serve as a basis for long-term
prediction of changes in environmental radioactive contamination in
Fukushima. For example, Putyrskaya et al. (2009) presented the results of
more than ten years of observation on the behaviour of
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
Selected irrigation ponds of Suzuuchi (SU), Funasawa (FS), Inkyozaka (IZ)
and Kashiramori (KM) are located in the city of Okuma within a radius of 10 km from FDNPP (Fig. 1). The surface area of these ponds of SU, FS, IZ and
KM was 4100, 10 700, 6500 and 8100 m
Location of study sites in Fukushima Prefecture and in Okuma town.
We had collected 2 L of water samples from the four ponds approximately once
a month since August 2015 to August 2017. Then, water samples were filtered
using 0.45
Summary of
Particulate
Temporal variations in total, particulate, dissolved
Soil and bottom sediment samples were collected in June 2016. Soils at a
depth of 30 cm using a liner core sampler DIK-110C (DAIKI, Japan) with a
plastic cylinder insert 5 cm in diameter. In laboratory, surface soils, to
the depths of 3–5 cm, were cut for every 1–2 cm, and then remained
subsurface soils were cut by 3–5 cm. Each soil sample was dried at 50
Each bottom sediment sample was dried at 50
The proportion of
The exchangeable fraction of the soil and bottom sediment were extracted
with 1 M
The observation results are presented in Table 1. Particulate
Figure 2 shows temporal variations in total, particulate and dissolved
Decreasing trends of
Temporal variations in
The vertical distributions of
Vertical distribution of
The depth at which the soil contains 90 % of the inventory of
At least 95 % of
Proportion of exchangeable, organic and particle bound fractions
of
Putyrskaya et al. (2009) demonstrated that percentage of exchangeable
These mobilities may have led to the vertical migration of
We investigated the behaviour of
In addition, the sequential extractions of sediment samples showed a higher
proportion of
The data can be accessed by request to authors.
YW: Sampling, analyses and discussion as corresponding author. AK: Sampling, sample treatment and discussion. TW: Sampling, and discussion. TT: Sample analyses, and discussion. YI: Sampling, analyses, and discussion. KN: Sampling, discussion, and facilitating observation. IB: Sampling, sample treatment, and discussion.
The authors declare that they have no conflict of interest.
This article is part of the special issue “Land use and climate change impacts on erosion and sediment transport”” It is a result of the ICCE Symposium 2018 – Climate Change Impacts on Sediment Dynamics: Measurement, Modelling and Management, Moscow, Russia, 27–31 August 2018.
This study was supported by a grant-in-aid from the Kurita Water and Environment Foundation (No. 15B098 and 16K023). This study was partly supported by JSPS KAKENHI project 18H03389. The authors would like to thank Kenji Watanabe, Azusa Goto and Jun Obara in Institute of Environmental Radioactivity, Fukushima University for supporting sampling and measurements in this study.
This research has been supported by the Kurita Water and Environment Foundation (grant no. 15B098 and 16K023) and partly supported by JSPS KAKENHI (project 18H03389).