Influence of irrigation water intake on local increase of radiocesium activity concentration in rice plants near a water inlet.

To identify the cause of the phenomenon that rice plants close to the water inlet contain relatively higher radiocesium within a paddy field plot, we conducted a field experiment by establishing experimental channel using polypropylene corrugated sheets, and sampling surface water, paddy soil and rice plants according to the distance from the water inlet in 2014 and 2015. It was found that the Cs activity concentrations in both dissolved and particulate forms in paddy surface water presented a declining trend from the water inlet towards the outlet. The Cs activity concentration in paddy soil in the harvesting season and those of brown rice and rice straws were highest at 1-2 m from the water inlet.

Input and output pathways determining potassium budgets in two paddy fields subjected to countermeasures against radiocesium in Fukushima, Japan.

Countermeasures to reduce radiocesium (134Cs and 137Cs) uptake by crops have been implemented in farmlands affected by the Fukushima nuclear accident in 2011. A widely practiced countermeasure is the application of potassium (K). Long-term soil K maintenance is a key issue due to the long physical half-life of 137Cs (30 years).

Measurement and estimation of radiocesium discharge rate from paddy field during land preparation and mid-summer drainage.

In this research, we evaluated the range of (137)Cs discharge rates from paddy fields during land preparation and mid-summer drainage. First, we investigated (137)Cs discharge loads during land preparation and mid-summer drainage and their ratio to the (137)Cs inventory of paddy field soil. We found that total discharge rates were 0.

¹³⁷Cs in irrigation water and its effect on paddy fields in Japan after the Fukushima nuclear accident.

There is concern that radiocesium deposited in the environment after the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011 will migrate to paddy fields through hydrological pathways and cause serious and long-lasting damage to the agricultural activities. This study was conducted in the Towa region of Nihonmatsu in the northern part of Fukushima Prefecture, Japan, (1) to quantify (137)Cs in stream water used to irrigate paddy fields by separating the dissolved and particulate components in water samples and then fractionating the particulate components bonded in different ways using a sequential extraction procedure, and (2) to determine the amounts of radiocesium newly added to paddy fields in irrigation water relative to the amounts of radiocesium already present in the fields from the deposition of atmospheric fallout immediately after the FDNPP accident. Three catchments were studied, and the (137)Cs activity concentrations in stream water samples were 79-198 mBq L(-1) under stable runoff conditions and 702-13,400 Bq L(-1) under storm runoff conditions.