Radioactive Cesium Concentrations Research Articles

Quantitative evaluation of radioactive cesium concentration in leachate and landfill waste at a municipal waste final disposal site in Fukushima prefecture

Quantitative evaluation of radioactive cesium concentration in leachate and landfill waste at a municipal waste final disposal site in Fukushima prefecture

Relationship between stable cesium concentration and body size of Japanese flounder Paralichthys olivaceus and the effect of a size-dependent shift in diet.

To understand the relationship between the radioactive cesium (Cs) concentration in muscle of Japanese flounder Paralichthys olivaceus and the species' biological characteristics (size, sex, and age) under conditions of ecological equilibrium (i.e., distributed among ecosystem components over sufficient time, and with nearly constant ratios of Cs concentration in organisms to the concentration in water) as existed before the accident at the Fukushima Dai-ichi Nuclear Power Station (FDNPS), Japan, in 2011, we examined stable Cs, as it is thought to exist in equilibrium in the environment and behave similarly to radioactive Cs in aquatic animals. The concentration of stable Cs in 241 P. olivaceus (range 216-782 mm total length [TL]) collected in Sendai Bay, approximately 90 km north of the FDNPS, in June-July 2015 was expressed as an exponential function with size as an independent variable; the results show the concentration of stable Cs doubled with an increase in TL of 442 mm. Next, to evaluate the cause of the size-dependent change in stable Cs concentration, we examined 909 individuals (200-770 mm TL) collected in September 2013-July 2015 to determine their feeding habit based on size. Analysis of the frequency of occurrence of prey organisms in stomach contents showed that sand lance Ammodytes japonicus (55-180 mm standard length [SL]) was the most consistently consumed across size classes. Analysis on a wet-mass basis showed that A. japonicus and anchovy Engraulis japonicus (65-130 mm SL) were the main food of P. olivaceus sized 200-599 mm TL, whereas chub mackerel Scomber japonicus (120-230 mm SL) and two species of flatfishes (180-205 mm SL) were abundant in the diet of P. olivaceus sized ≥600 mm TL. All these prey items were presumed to have similar concentrations of stable Cs. Based on the above, the effect of diet on the relationship between stable Cs in muscle and fish size was considered negligible. That the diet of P. olivaceus largely did not change with size was also confirmed by C and N stable isotope ratios in P. olivaceus and their prey species. Therefore, the Cs-size relationship is probably determined by changes in the balance between the rate of Cs intake from food and seawater and the excretion rate during growth, both of which change as functions of body mass. Values of stable Cs concentrations among environmental components and animals appear to be a valid indicator for understanding the radioactive Cs distribution in the marine environment and aquatic animals under the equilibrium state, as existed before the 2011 nuclear accident.

Effect of radioactive cesium-rich microparticles on radioactive cesium concentration and distribution coefficient in rivers flowing through the watersheds with different contaminated condition in Fukushima

Radioactive cesium-rich microparticles (CsMPs) derived from the Fukushima Daiichi Nnuclear Power Plant accident were detected from soils and river water around Fukushima Prefecture, Japan. Because CsMPs are insoluble and rich in radioactive cesium (RCs), they may cause the overestimation of solid-water distribution coefficient (Kd) for RCs in the water. Previous studies showed the proportion of RCs derived from CsMPs on RCs concentration in soils collected from areas with different contaminated levels. Because the proportion of RCs concentration derived CsMPs to the RCs concentration of soils in the less contaminated areas is higher than that in the highly contaminated areas, the effect of CsMPs on particulate RCs concentration in river water may be larger in the less contaminated areas. However, the difference in the effects of CsMPs on the particulate RCs concentration and Kd in river water flowing through watersheds with different contaminated levels has not been clarified. In this study, we investigated the effect of CsMPs on the particulate RCs concentration and Kd in two rivers, Takase River and Kami-Oguni River, flowing through the watersheds with different RCs contaminated levels in Fukushima Prefecture.CsMPs might enter rivers due to soil erosion because they were detected only in some samples collected from both rivers during flood events. CsMPs accounted for more than half of particulate RCs concentration in some water samples collected in the flood condition. In particular, the proportion of CsMPs in particulate RCs for the Kami-Oguni River was greater than that for the Takase River. However, when evaluating for the entire water sampling in the flood condition, a proportion of RCs concentration derived from CsMPs in the average RCs concentrations per unit mass of SS in both river waters collected in the flood condition was not large. CsMPs might temporarily increase the particulate RCs concentration and Kd in the flood event, but CsMPs did not significantly affect them when evaluated throughout the event.

Radiation dose and gene expression analysis of wild boar 10 years after the Fukushima Daiichi Nuclear Plant accident

The Fukushima Daiichi Nuclear Power Plant accident led to contamination with radioactive cesium in an extensive environment in Japan in 2011. We evaluated the concentration of radioactive cesium in the skeletal muscles of 22 wild boars and the expression of IFN-γ, TLR3, and CyclinG1 in the small intestine and compared them with those of wild boar samples collected from Hyogo prefecture. The average 137Cs radioactivity concentration in wild boars in the ex-evacuation zone was 470 Bq/kg. Most of samples still showed radioactivity concentration that exceeded the regulatory limit for foods, but the dose remarkably decreased compared with samples just after the accident. IFN-γ expression was significantly higher in wild boars in the ex-evacuation zone than in samples from Hyogo prefecture. TLR3 expression was also upregulated. CyclinG1 expression also tended to be high. Hence, wild boars might have received some effects of low-dose radiation, and immune cells were activated to some extent. However, pathological examination revealed no inflammatory cell infiltration or pathological damage in the small intestine of wild boars in the ex-evacuation area. Long-term monitoring would be necessary, but we consider that the living body responds appropriately to a stimulus from a contaminated environment.

CHARACTERISATION OF RADIOACTIVE CAESIUM IN SEDIMENTS AT THE NOGAWA RIVER, JAPAN.

The TEPCO Fukushima Daiichi Nuclear Power Plant accident that occurred in March 2011 resulted in the release of radioactive caesium into the environment. The radioactive caesium has been detected in the Tama River watershed. Previous investigations have shown that the concentration of radioactive caesium in sediment was relatively high in the Nogawa River. In this study, the relationship between the concentration of radioactive caesium in the sediment and the sediment characteristics was investigated. We found that 137Cs concentration in the tributary sediment has difficulty migrating downstream, while exhibiting a strong correlation with the amount of organic matter and a correlation with the clay, silt layer. Based on the results, we inferred that 137Cs is deposited together with the organic matter and clay, silt layer in the sediment and migrates at a slower pace than that in the mainstem.

Radioactivity concentration measurements in fish and shellfish samples from the west coast of Canada after the Fukushima nuclear accident (2011–2018)

Radioactive contamination of the Pacific Ocean following the Fukushima nuclear accident has raised public concern about seafood safety, particularly in coastal Indigenous communities. To address this, Health Canada and partners have collected and analyzed a total of 621 samples of commonly consumed salmon, ground fish, and shellfish from the Canadian west coast from 2011 to 2018. While the vast majority of the 137Cs and 134Cs levels were below the Minimum Detectable Concentration (MDC, typically 0.7–1.0 Bq kg−1 fw for a 6 h counting), further examination of 19 fish samples revealed 137Cs concentrations of 0.17–0.53 Bq kg−1 fw with an average value and uncertainty (k = 1) of 0.29 ± 0.02 Bq kg−1 fw. Of these, only two samples were found to have trace levels of 134Cs likely derived from the Fukushima accident. The global fallout contribution from atmospheric nuclear weapons testing to the observed 137Cs in these two samples was determined to be 0.26 ± 0.08 Bq kg−1 fw (49 ± 14%) and 0.12 ± 0.02 Bq kg−1 fw (24 ± 4%) for collection years 2015 and 2016, respectively. The annual average level of 137Cs in fish and shellfish was also determined by spectral summation for collection years 2014–2018. In fish, 137Cs levels determined through spectral summation were relatively constant (0.18–0.25 Bq kg−1 fw) with an average value and uncertainty of 0.21 ± 0.02 Bq kg−1 fw. By contrast, 38 shellfish samples (bivalves) were measured and revealed no radiocesium or other anomalies in either tissue or shell. In all, measurements over eight years showed that the radioactivity in fish and shellfish was dominated by natural radionuclides and that the level of anthropogenic radionuclides, as indicated by the radioactive cesium content, remained small. An upper bound for ingested dose from 137Cs was determined to be approximately 0.26 μSv per year, far below the worldwide average annual effective dose of 2400 μSv from exposure to natural background radiation. We can therefore conclude that fish, such as salmon, ground fish, and shellfish from the Canadian west coast are of no radiological health concern despite the Fukushima Dai-ichi nuclear accident of 2011.

Radioactive cesium contamination in persimmon tree after Fukushima Daiichi Nuclear Power Plant accident – the difference of radioactive cesium concentration of fruit on each branch in the same tree

Radioactive cesium contamination in persimmon tree after Fukushima Daiichi Nuclear Power Plant accident – the difference of radioactive cesium concentration of fruit on each branch in the same tree

Study on the Concentration of Radioactive Cesium in the Environment after the Fukushima Daiichi Nuclear Power Plant Accident

The Tohoku-Pacific Ocean Earthquake that occurred on March 11, 2011 and the resulting tsunami caused the loss of many people and extensive damage in a wide area. Among the anthropogenic radionuclides dispersed from the Fukushima Daiichi Nuclear Power Plant, 134Cs and 137Cs have very long half-lives of approximately 2 years and 30 years, respectively, and there are concerns about their uptake into soil and living things. This paper describes a study conducted by the authors' group on radiocesium activity concentrations in the environment.

Numerical Study on Basic Behavior of Seepage Water Flowing through Soil in Waste Disposal Sites

Analyzes of leachate from several landfill sites in Fukushima Prefecture have shown that most of the sites have radioactive cesium concentrations as low as a few becquerel, but in some disposal sites it showed values exceeding 10 Bq/kg. In order to clarify the behavior of seepage water flowing inside the waste disposal site under the conditions that do not contain radioactive materials, therefore, numerical simulations were conducted using a system that simply simulates a structure of landfill materials accumulated in layers in the vertical direction. The effect of porosity in landfills on seepage water behavior was investigated. When the porosity is large, there are large spaces in the landfill, and it takes time for seepage water to fill the spaces. As a result, it was found that the time required for seepage water to move to the bottom of the waste disposal site was longer than when the porosity was small. The prospect of qualitatively evaluating the tendency of movement behavior of seepage water by simulation was obtained.

Effect of Csmps on Radioactive Cesium Concentration and Distribution Coefficient in Rivers Flowing in the Watersheds with Different Contaminated Condition in Fukushima

Effect of Csmps on Radioactive Cesium Concentration and Distribution Coefficient in Rivers Flowing in the Watersheds with Different Contaminated Condition in Fukushima

Effect of Csmps on Radioactive Cesium Concentration and Distribution Coefficient in Rivers Flowing in the Watersheds with Different Contaminated Condition in Fukushima

Effect of Csmps on Radioactive Cesium Concentration and Distribution Coefficient in Rivers Flowing in the Watersheds with Different Contaminated Condition in Fukushima

Radiocesium Concentration in Commercially-Available Foods Produced in Japan: 2017-2019.

We investigated the concentration of radioactive cesium (r-Cs: 134Cs and 137Cs) in commercially-available foods to confirm the effectiveness of pre-shipment radioactive material inspections mainly conducted by local governments. We focused on selected production areas and foods with high probability of r-Cs detection. To this end, we evaluated 715, 685, and 683 samples using scintillation spectrometer and high-purity germanium γ-spectrometer in fiscal years 2017, 2018, and 2019, respectively. The results accounted for 9 samples (1.3%), 10 samples (1.5%), and 5 samples (0.7%) for each fiscal year exceeded the standard limit of radioactive material (100 Bq/kg as r-Cs concentration for general foods). Although we selected and evaluated foods with high probability of r-Cs detection, percentage of samples exceeding the standard limit in each fiscal year was very low, less than 2% to be exact. This suggests that food management system, including pre-shipment inspections, were effectively functioning. In addition, samples exceeding the standard limit were bound to edible wild plants and wild mushrooms, and log-cultivated mushrooms. The former is consider to be difficult for cultivation/feeding control, and the latter was know to be parts of foods greatly affected by radioactive materials. This suggests that the concentration of r-Cs in these items remains at relatively high levels. In contrast, r-Cs was not detected in items with controalble cultivation/feeding. Based on these observations, it is better to be inspected on more difficult-to-cotrol cultivation/feeding items, in order to achieve further streamlining and improving of inspection efficiency. Our results indicate that r-Cs concentration in commercially-available foods of easy-to cultivation/feeding control, such as general vegetables, fruits, and meat, have been well-controlled in Japan, however, difficult-to-cultivation/feeding control items need to be more paid attention to r-Cs concentrations.

Quantitative modeling of radioactive cesium concentrations in large omnivorous mammals after the Fukushima nuclear power plant accident

Large quantities of radionuclides released by the Fukushima nuclear power plant accident entered terrestrial and marine ecosystems. The resulting radioactive contamination of large omnivorous wild mammals such as wild boar (Sus scrofa) and Asian black bear (Ursus thibetanus) varied greatly depending on location, season, and time after the accident. Quantitative modeling of how such factors influence radionuclide burdens in these species is important for enhancing current knowledge of chronic radionuclide exposure consequences in mammalian populations, and for assessing potential human risks from consumption of contaminated animal meat. Here we modeled the time course of radioactive cesium (134Cs + 137Cs) concentrations in boar and black bears from Fukushima Prefecture over ~ 7 years after the accident, using nonlinear robust and quantile regressions and mixed-effects modeling. To estimate predictive performance, models fitted to the full data set were compared with those fitted only to the first 3.5 years of data, and tested on the last 3.5 years of data. Ecological half-lives for radioactive cesium, and magnitudes and phase shifts for sinusoidal seasonal oscillations in cesium burdens, were estimated by each analysis method for each species. These results can improve the understanding and prediction of radionuclide concentrations in large mammals that inhabit radioactively contaminated areas.

Changes in radioactive cesium concentrations from 2011 to 2017 in Fukushima coastal sediments and relative contributions of radioactive cesium-bearing microparticles

Sedimentary cesium-137 concentrations around the Fukushima Daiichi Nuclear Power Plant (FDNPP) were measured from 2011 to 2017 at eight stations. Although high values were observed until 2013, decreasing trends were observed at the surface sediments of seven stations. We isolated 25 radioactive Cs-bearing microparticles (CsMPs; 1.0–5385 Bq per particle). The contribution ratio of CsMPs to each sample ranged from 4.1% to 99.5% (median 58.8%), with the contribution ratio of the CsMPs in the southern part of the FDNPP was low compared to that from the northern part. In the southern part of the FDNPP, small CsMPs that could not be isolated in this study were present in large quantities immediately after the accident, and gradually diffused away and/or were dissolved over time. In contrast, the CsMPs in the northern part of the FDNPP have most likely accumulated over time, as suggested by the silty nature of the sediments there.

Functionalized geopolymer foams for cesium removal from liquid nuclear waste

Geopolymer foam hosting a 3D network of interconnected pores was synthetized and functionalized with a potassium copper hexacyanoferrate [K2CuFe(CN)6] in order to decontaminate radioactive liquid waste containing cesium. The Geopolymer Foam (GF) and Functionalized Geopolymer Foams (FGF) were characterized using a panel of characterization techniques (SEM, TEM, XRD …) before studying their capacity to remove selectively cesium from the solution. K2CuFe(CN)6 homogeneously precipitates on the pore walls of the foam and into the mesoporous network. Exploiting kinetic and adsorption isotherms in various solutions (deionized water, fresh water and fresh water with excess of sodium), a comparative study between the GF and FGF was undertaken. In presence of competitive ions into the solution, the capacity of both materials decreases with respect to the deionized water. The mechanism of exchange is Na+ ↔ Cs+ and K+ ↔ Cs+ for GF and FGF respectively. Although the GF material presents some very high performances in term of ion exchange, in excess of sodium ions, the GF material completely loses its capacity with respect to the FGF that remains constant up to 1 mol/l−1. FGF is therefore very selective with regard to the cesium if other cations coexist into the solution. This is also confirmed by experiments performed in radioactive environment for very low concentration of radioactive cesium where the distribution coefficient (Kd) for the FGF reaches in average 3.5 105 ml g−1 that is ten times higher than for the GF material.

Estimation of water seepage rate in the active crater lake system of Kusatsu-Shirane volcano, Japan, using FDNPP-derived radioactive cesium as a hydrological tracer

We describe here a first attempt to estimate the water seepage rate of an active crater lake using radioactive cesium dispersed into the environment by the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011 as a hydrological tracer. Kusatsu-Shirane volcano is one of the most active volcanoes in Japan and has an active crater lake named Yugama. There is no outflow such as a river from Yugama crater lake. The content level of stable cesium (133Cs) in Yugama water was almost constant at 15–20 nM during the sampling period of Nov. 2011 to Nov. 2014. In contrast to 133Cs, however, the radioactive cesium (134Cs and 137Cs) concentrations in Yugama water decreased at a more rapid rate than expected by radioactive decay. Based on the decreasing rates of activity concentrations of 134Cs and 137Cs in Yugama water during the three years between 2012 and 2014, it is estimated that 700–800 m3 of the Yugama water, which corresponds approximately to 0.1% of the total volume, leaks through the lakebed per day. In the estimation, balance between leakage of radioactive cesium contaminated water though lake bed and geothermal inflow of radioactive cesium-free water in the volcano was taken into account. Consequently, the water seepage rate of the Yugama crater lake was calculated to be 8.1–9.3 L s−1.

Content of Technogenic Radionuclides in Water, Bottom Sediments, and Benthos of the Kara Sea and Shallow Bays of the Novaya Zemlya Archipelago

Abstract—The radioactive cesium content determined in sea water of the Novaya Zemlya archipelago bays and offshore zone during the expedition of R/V Akademik Mstislav Keldysh in 2016 year seemed to correspond to the global fallout (1 Bq /m3). The plutonium content in water is slightly higher. The activity of neptunium in water is an order of magnitude higher than that of plutonium (0.76–1.89 Bq/m3), although its content in the global fallout is almost two orders of magnitude lower than the plutonium content. The activity of plutonium in the bottom sediments of the Kara Sea is 0.2−3.8 Bq/kg, while that of radioactive cesium is 0.5−0.6 Bq/kg, reaching 21 Bq/kg in the Yenisei mouth. Analysis of benthic samples showed that the content of radioactive cesium and plutonium in samples taken in the bays of the Novaya Zemlya archipelago is below the detection limit. The neptunium content in the benthic samples is within 1−80 Bq/kg wet weight. It was shown that the content of neptunium in benthos is one of the indicators of radioactive pollution of the marine environment.

Spatial variation in sedimentary radioactive cesium concentrations in Tokyo Bay following the Fukushima Daiichi Nuclear Power Plant accident

Cesium-137 concentrations in sediment (137Cs) at Tokyo Bay were measured at 26 stations during 2017. Average 137Cs concentrations at the Arakawa river mouth (117 ± 46 Bq kg−1) were approximately six times higher than those of the other stations in the bay (20 ± 16 Bq kg−1). There were radiocesium-bearing microparticles in the bay sediment as well as in suspended matter of Fukushima coastal waters. Radioactivity of radiocesium-bearing microparticles was estimated to be 0.12 Bq. However, the contributions of radiocesium-bearing microparticles to each 137Cs concentration of the bulk sample were low; 3% was the maximum. The 137Cs inventory in sediment at the entire bay was 0.67 TBq, showing that a large amount of 137Cs was supplied to the bay from the river following the Fukushima Daiichi Nuclear Power Plant accident. Approximately 9.2% of the 137Cs which was fallout in the drainage basin has already flowed into the bay from the watershed, which is approximately 3.2 times higher than that of a previous estimate.

A Portable Radioactivity Detection System for Outdoor Measurement of Concentration of Radioactive Caesium in a Mushroom Bed Log at a Low-level Contaminated Environment

A Portable Radioactivity Detection System for Outdoor Measurement of Concentration of Radioactive Caesium in a Mushroom Bed Log at a Low-level Contaminated Environment

Effects of Treatment Time and Thickness of Meat on the Removal of Radioactive Cesium from Beef Slices by Boiling and Water Extraction

Boiling effectively decreased radioactive cesium concentrations in beef. Water extraction was also effective but not as effective as boiling. The decontamination effect increased with treatment time. The decontamination effect was inversely proportion to the square of the thickness of the beef slice.