Inspections of radiocesium concentration levels in rice from Fukushima Prefecture after the Fukushima Dai-ichi Nuclear Power Plant accident

We summarize the inspections of radiocesium concentration levels in rice produced in Fukushima Prefecture, Japan, for 3 years from the nuclear accident in 2011. In 2011, three types of verifications, preliminary survey, main inspection, and emergency survey, revealed that rice with radiocesium concentration levels over 500 Bq/kg (the provisional regulation level until March 2012 in Japan) was identified in the areas north and west of the Fukushima nuclear power plant. The internal exposure of an average adult eating rice grown in the area north of the nuclear plant was estimated as 0.05 mSv/year. In 2012, Fukushima Prefecture authorities decided to investigate the radiocesium concentration levels in all rice using custom-made belt conveyor testers. Notably, rice with radiocesium concentration levels over 100 Bq/kg (the new standard since April 2012 in Japan) were detected in only 71 and 28 bags out of the total 10,338,000 in 2012 and 11,001,000 in 2013, respectively. We considered that there were almost no rice exceeding 100 Bq/kg produced in Fukushima Prefecture after 3 years from the nuclear accident, and the safety of Fukushima\u27s rice were ensured because of the investigation of all rice

Short day length-induced decrease of cesium uptake without altering potassium uptake manner in poplar

Short day length-induced alteration of potassium (K) localization in perennial trees is believed to be a mechanism for surviving and adapting to severe winters. To investigate the relationship between cesium (Cs) and K localizations, a model tree poplar, hybrid aspen T89, was employed. Under short day length conditions, the amount of 137Cs absorbed through the root and translocated to the root was drastically reduced, but 42K was not. Potassium uptake from the rhizosphere is mediated mainly by KUP/HAK/KT and CNGC transporters. In poplar, however, these genes were constantly expressed under short-day conditions except for a slight increase in the expression a KUP/HAK/KT gene six weeks after the onset of the short-day treatment. These results indicated that the suppression of 137Cs uptake was triggered by short day length but not regulated by competitive Cs+ and K+ transport. We hypothesize that there are separately regulated Cs+ and K+ transport systems in poplar

Removal of radioactive Cs from gravel conglomerate using water containing air bubbles.

Remediation of sites contaminated with radioactive material such as Cs is important because of the risk posed to human health. Here, we report the effectiveness of water containing air bubbles with a diameter around 100 nm (nanobubbled water, NB water) for the removal of radioactive Cs. Laboratory experiments confirmed that NB water is more effective than purified water and as effective as water with neutral detergent in the removal of Cs-137 from gravel. Moreover, NB water retains its effectiveness even after storage for 7 d. Finally, NB water produced onsite from tap water was found to be effective for removal of radioactive Cs from gravel conglomerate in Fukushima, Japan

Effect of different Cs concentrations on overall plant growth and Cs distribution in soybean

The absorption and dynamics of Cs in crops can be measured and examined using not only 137Cs but also 133Cs, a stable isotope which can be analyzed in a regular laboratory. When 133Cs is used, however, the concentration of added 133Cs must be set higher than that in the soil solution due to the detection sensitivity of inductively coupled plasma optical emission spectrometry (ICP-OES). There is concern that such high Cs concentrations may adversely affect crops and interfere with Cs dynamics. Using soybean as a test product, we first examined the initial growth of soybean cultivated under exposure to solutions with different 133Cs concentrations. In combination with each 133Cs concentration, two potassium (K) concentrations were tested. Results show that at both K concentrations, growth was inhibited under 133Cs concentrations higher than 1 × 10−3 mol L−1. Soybeans cultivated at 133Cs concentrations higher than 1 × 10−6 mol L−1 can be subject to ICP-OES for measuring 133Cs concentrations in the plant tissue. Next, soybeans cultivated under different 133Cs concentrations throughout growth were examined for Cs distribution in the plants. The distribution patterns of Cs in soybean plants cultivated at 133Cs concentrations equivalent to those found in the soil were almost identical to those in plants cultivated at measurable 133Cs concentrations (1 × 10−6–1 × 10−4 mol L−1) as measured with ICP-OES. Therefore, in our investigation, 133Cs distribution in soybean plants treated with up to 1 × 10−4 mol L−1 was considered equivalent to that in plants cultivated in the field

Monitoring inspection for radiocesium in agricultural, livestock, forestry and fishery products in Fukushima prefecture

We selected and re-categorized the monitoring data opened by the government of Fukushima prefecture focusing on the radiocesium concentrations in four agricultural products, from the data on 90,000 samples analyzed during 3 years. Radioactivity was found to be high during 3 months after the accident because of direct fallout. The internal exposure in the area with the highest contamination area of rice during the first 3 months was calculated and estimated to be 0.75 mSv year−1. The radioactivity in foods products rapidly decreased after 3 months later, but in the case of some forestry products and fish, there are still some products in which radioactivity was above the regulated value, 100 Bq kg−1

Correlation Between Radiation Measurement on the Field Slopes Using KURAMA-II(Kyoto University RAdiation MApping System) and Environmental Radioactivity in the Soil Depth Direction

Part of the Springer Proceedings in Physics book series (SPPHY, volume 275)Using KURAMA-II (Kyoto University Radiation Measurement System), we investigated the environmental radioactivity after decontamination in the rice fields of Iitate Village, Fukushima Prefecture. We compared the cross-correlation between the measurement results of KURAMA-II and those of actual soil sampling to confirm the measurement error, especially in the sloping area around the rice field. The results showed an excellent agreement between the soil sample of 5 cm surface layer even in slope

Rhizosphere modelling reveals spatiotemporal distribution of daidzein shaping soybean rhizosphere bacterial community

ダイズの分泌物「ダイゼイン」が根圏微生物叢を形成することを解明 --根から数ミリの土壌で働く植物特化代謝物--. 京都大学プレスリリース. 2020-01-14.Plant roots nurture a wide variety of microbes via exudation of metabolites, shaping the rhizosphere's microbial community. Despite the importance of plant specialized metabolites in the assemblage and function of microbial communities in the rhizosphere, little is known of how far the effects of these metabolites extend through the soil. We employed a fluid model to simulate the spatiotemporal distribution of daidzein, an isoflavone secreted from soybean roots, and validated using soybeans grown in a rhizobox. We then analysed how daidzein affects bacterial communities using soils artificially treated with daidzein. Simulation of daidzein distribution showed that it was only present within a few millimetres of root surfaces. After 14 days in a rhizobox, daidzein was only present within 2 mm of root surfaces. Soils with different concentrations of daidzein showed different community composition, with reduced α‐diversity in daidzein‐treated soils. Bacterial communities of daidzein‐treated soils were closer to those of the soybean rhizosphere than those of bulk soils. This study highlighted the limited distribution of daidzein within a few millimetres of root surfaces and demonstrated a novel role of daidzein in assembling bacterial communities in the rhizosphere by acting as more of a repellant than an attractant