Calibration experiments for radon in drinking water measurements using portable-type electrostatic-collection radon monitors

Portable-type electrostatic-collection radon monitors (RAD7) are often used for in-situ measurements of radon in water. In this study, we evaluated the calibration factors and their uncertainties for two RAD7 monitors based on comparative measurements with the liquid scintillation counting method. In the first experiment, we found that both RAD7 monitors had relatively large uncertainties due to leakage of radon gas that bubbled from the gaps between the lids of the desiccant container and the glass vial. Therefore, for the second experiment, these gaps were closed as much as possible using parafilm and clay, respectively. As a result, the relative uncertainties for both RAD7 monitors were significantly decreased. Furthermore, we collected spring water samples to confirm the reliability of radon concentrations. After closing the leakage point, the uncertainty of radon concentrations in spring water we measured using the typical protocol of the RAD7 were significantly lower, which improves the measurement.

Effect of drought stress or soil pH on cesium accumulation in Napier grass

Radio-cesium (Cs) decontamination efficiency by plants is supposedly affected by environmental conditions. To elucidate the factors influencing the unstable ¹³⁷Cs-decontamination efficiency, we first examined the influence of drought or soil pH on Cs accumulation using cesium-133 (¹³³Cs) using Napier grass (Pennisetum purpureum Schum.) grown under pot conditions. The experiment was performed on three different conditions with 150 µM ¹³³Cs applied to soil: low pH (L-pH, pH = 5.6 ± 0.0), near-neutral pH (N-pH, pH = 6.6 ± 0.1), and the combination of low pH and drought stress (Drought). Drought stress had prominent negative effects on plant height, aboveground dry matter weight (DW_above), ¹³³Cs concentrations in aboveground or root (Cs_above or Cs_root) parts, or ¹³³Cs total content in the part aboveground (Cs-T). ¹³³Cs concentration and total content in Drought conditions were reduced by 44.1% and 60.0% aboveground and 63.6% and 66.0% in root parts compared with counterpart normal soil moisture conditions (L-pH), respectively. Conversely, there were no significant effects of soil pH on Cs_above, Cs_root, or Cs-T in L-pH and N-pH conditions. Chlorophyll fluorescence parameters (F_v/F_m, F_v/F₀) and the temperature in leaves were negatively affected by drought stress or soil pH conditions. From our results, drought strongly influenced plant growth and Cs accumulation in plants compared with soil acidity. Therefore, soil moisture appears to be a significant factor in maintaining ¹³⁷Cs-decontamination efficiency by Napier grass.

PERFORMANCE EVALUATION OF COMMERCIAL SCINTILLATION COCKTAILS FOR LOW-LEVEL TRITIUM COUNTING BY HIGH-CAPACITY LIQUID SCINTILLATION COUNTER

Low-background liquid scintillation counter is one of the popular measuring instruments used to investigate tritium radioactivity in environmental media. These instruments require the liquid sample and organic solvent to be mixed for tritium measurement. In the European Union, the registration, evaluation, authorization and restriction of chemicals regulation was established to control the use of chemical substances of very high concern. It is important to find continuously available alternative reagents. In this paper, a performance evaluation was conducted using four scintillation cocktails according to Japanese conventional procedure; although one of them, Gold Star LT2, contains nonylphenol ethoxylate, it will continue to be available for research and development. From the evaluation results it was confirmed that Gold Star LT2 would be a satisfactory alternative scintillator, which is similar performance of Ultima Gold LLT.

SPECIATION OF CESIUM ISOTOPES IN RIVER WATER: A CASE STUDY IN THE UKEDO RIVER

137Cs in river systems can be taken up by aquatic animals. In this paper, total 137Cs concentration in the Ukedo River system and 137Cs presence in dissolved, acid-soluble and -insoluble fractions in river water samples were determined. Total 137Cs concentration had the maximum value of 2.08 Bq kg-1 below the Ogaki Dam in May 2012. In the base flow condition, > 87% of 137Cs existed in the dissolved state, and the acid-soluble state and the insoluble state were <13% and the undetectable level, respectively. After the heavy rain event, the particulate fraction (acid-soluble state + insoluble state) was elevated to 65%, which corresponds to twice as much as that in the base flow condition. Particulate 137Cs, especially the acid-soluble Cs, can play a role when taken into the food chain in aquatic ecosystems.

INFLUENCE OF SAMPLING FLOW RATE ON THORON EXHALATION RATE MEASUREMENTS BY THE CIRCULATION METHOD

Researchers have used various methods to obtain the exhalation rates of radon and thoron from soil and building materials. One of the typical methods for radon exhalation rate is the circulation method using an accumulation container, an external or internal sampling pump and a continuous radon monitor. However, it is necessary to consider sampling flow rate if this method is applied to exhalation rate measurement for thoron due to its short half-life. Based on a calibration experiment, the measured thoron concentrations obtained by an electrostatic collection type radon and thoron monitor (RAD7) were found to be influenced strongly by the sampling flow rate. It was also found that the thoron exhalation rate from a soil sample depended on the pressure difference which was proportional to the increasing sampling flow rate. The thoron exhalation rate measured at the generally used sampling flow rate of the internal sampling pump of the RAD7 was overestimated compared with the value at 0 L min-1.

Multiple Evaluation of Typical Heavy Metals Pollution in Surface Soil and Road Dust from Beijing and Hebei Province, China

Soil and road dust are important receptors of heavy metals in the environment. Meanwhile, heavy metal could transfer to the atmosphere through resuspension. Due to the serious consequences and atmospheric haze in Jing-Jin-Ji area, it's important to evaluate the pollution level, particle size distribution and sources of heavy metals. For heavy metals in soil samples, similar concentrations to the background values and no obvious pollution or low-level pollution was presented. Higher concentration of Cu (78.9 mg/kg) and Zn (261 mg/kg) were found in road dust. The source appointment results showed that Mn, Co, Cr, Ni, Zn and Pb in soils and Cr, Co and Mn in road dust were mainly from the natural sources, while traffic source contributed to most of Cu, Zn and Pb in road dust. Different particle size distribution patterns were found in soils and road dusts, and the finest particles presented the highest heavy metal concentrations.

222Rn and 226Ra Concentrations in Spring Water and Their Dose Assessment Due to Ingestion Intake

²²²Rn and ²²⁶Ra concentrations of less than a few to several thousands of Bq L⁻¹ have been observed in several underground bodies of water around the world. Although regulations for these concentrations in water have been implemented internationally, there are currently no regulations in place in Japan. However, concentrations that exceed these internationally recognized regulatory values have also been observed in Japan. In this study, concentrations in spring water in the northern part of Japan were measured and the effective dose from intake of the water was evaluated. ²²²Rn concentrations were measured using a liquid scintillation counter, and ²²⁶Ra concentrations were measured using a high purity germanium detector after chemical preparation. The measured ²²²Rn concentrations (=12.7 ± 6.1 Bq L⁻¹) and ²²⁶Ra concentrations (<0.019–0.022 Bq L⁻¹) did not exceed the reference values set by international and European/American organizations. A conservative estimate of the annual effective ingestion dose of 8 μSv for ²²²Rn and ²²⁶Ra obtained in this study is much smaller than the estimated overall annual effective dose of 2.2 mSv from natural radiation to the Japanese population. However, this dosage accounts for 8% of the WHO individual dosing criteria of 0.1 mSv/year for drinking water.

Effects of environmental conditions, low-level potassium, ethylenediaminetetraacetic acid, or combination treatment on radiocesium-137 decontamination in Napier grass

Phytoextraction is widely used to remove environmental pollutants such as heavy metals or radionuclides from soil. It is important to understand how to enhance the accumulation of contaminants by plants. Previously, we found that Napier grass (Pennisetum purpureum Schum.) has the potential to effectively remove Cs (¹³³Cs and ¹³⁷Cs). In order to enhance the remediation efficiency of Napier grass, we evaluated the effects of low-level K (K), ethylenediaminetetraacetic acid (EDTA), or the combination of low-level K and EDTA (K+EDTA). We also examined the differences in ¹³⁷Cs decontamination between two cropping years (2018 and 2019). Overall, there were no prominent effects from the K, EDTA, or K+EDTA treatments on plant growth (plant height, tiller number), aboveground biomass, ¹³⁷Cs concentration, and ¹³⁷Cs removal ratio (CR) in 2 years. However, the aboveground biomass (P < 0.001), ¹³⁷Cs concentration (P < 0.001 in 2019 only), and CR (P < 0.001) in plants grown in the first growing period were significantly higher than in plants grown in the second growing period in both years. The mean ¹³⁷Cs concentration (P < 0.001) and total CR (P < 0.001) per year was significantly greater in 2019 than in 2018. The precipitation amount during the cultivation period in 2019 (1197 mm) was 1.8-fold higher than in 2018 (655 mm). In this study, the K, EDTA, and K+EDTA treatments had less effect plant growth than the natural environmental conditions. To enhance remediation efficiency, soil moisture is one important factor to produce more aboveground biomass to achieve high CR in Napier grass.

Determination of Nd isotopic composition in seawater using newly developed solid phase extraction and MC-ICP-MS

Determination of neodymium (Nd) isotopic composition in seawater is useful for tracing water masses and geochemical cycles for lithogenic elements in the ocean. A new separation procedure for determination of the Nd isotopic composition of in seawater samples was developed that offers enhanced sample throughput and improved measurement reliability. The procedure consists of conventional Fe hydroxide coprecipitation, solid phase extraction using DGA chelating resin column chromatography, and Ln Resin column chromatography to preconcentrate samples. High selectivity in HNO₃ medium and elution by low concentration HCl medium for Nd are characteristics of extraction using DGA Resin®, and they allowed an evaporation step to be omitted between the chromatographic steps. These chromatographic steps, using DGA Resin to separate REEs and Ln Resin® to remove Sm, were refined from a previous study. The procedural blank value of Nd was obtained as 2 pg (n = 6) from 3 L of water samples. Chemical yield of Nd from 3 L of seawater ranged within 90-95%. The developed procedure was combined with multiple collector-ICP-MS and applied to analysis of vertical seawater samples obtained from the western subarctic gyre of the North Pacific Ocean, where ε_Nd ranged from -1.29 ± 0.42 at the surface to -3.80 ± 0.41 at 4000 m depth. These results were validated by comparing them with results obtained by the conventional method verified in the GEOTRACES inter-calibration program.

Spatiotemporal change of cesium-137 in the Pacific coast of Tohoku, Japan: The mussel watch approach

We measured radiocesium in mussel tissue collected from the Pacific coast of Tohoku from 2011 to 2015 to investigate the temporal and spatial dynamics of radiocesium in the coastal area. Radioactive ¹³⁷Cs was detected in all the samples collected in 2011, but it was not found in samples from localities north of Sendai after 2012. In contrast, ¹³⁷Cs was detected in many sites in the Fukushima area even from 2012 to 2015. The fluctuation of ¹³⁷Cs concentration in mussel tissue seems to reflect the ¹³⁷Cs concentration in suspended particles in the seawater, suggesting that there was an influx of soil deposition and resuspension of seabed sediment. These results suggest that the ¹³⁷Cs concentration in mussel tissue sensitively indicates the ¹³⁷Cs concentration in the environment, and that the "mussel watch" approach is an effective way to understand the dynamics of radiocesium concentrations in coastal areas.

Support activities in Namie Town, Fukushima undertaken by Hirosaki University

This paper does not necessarily reflect the views of the International Commission on Radiological Protection.Several radiation monitoring research projects are underway on dose assessment, biological analysis, and risk communication under an agreement with Namie Town. Indoor radon and thoron progeny concentrations have been measured using passive-type monitors to estimate internal doses due to inhalation. In addition, airborne radiocaesium concentrations at five points in Namie Town have been analysed using a high-purity germanium detector to estimate internal doses for comparison with radon. External radiation doses from natural and artificial radionuclides have also been estimated using an in-situ gamma-ray spectrometer. Other support activities are mentioned briefly in this article.

Background and fingerprint characteristics of anthropogenic 236U and137Cs in soil and road dust samples collected from Beijing and Zhangjiakou, China

²³⁶U has attracted more attention as an environmental tracer in recent years. However, in-depth study of ²³⁶U in terrestrial environments is still rare in China. Data on ²³⁶U and ¹³⁷Cs concentrations in soil and road dust samples collected from Beijing and Zhangjiakou, China were obtained to demonstrate the background and distinct characteristics of anthropogenic ²³⁶U and ¹³⁷Cs. ²³⁶U and ¹³⁷Cs were detected in the range of (1.10-7.90) × 10⁷ atoms g^-1 and below the method limits of detection to 5.30 Bq kg^-1. A clear characteristic was observed in road dust, where ²³⁶U concentrations increased with decreasing of sample particle size. Soil samples showed an irregular characteristic, but the highest ²³⁶U concentrations were observed in particle size fraction of <0.053 mm in both samples. This phenomenon was caused by U chemical properties, higher specific surface areas and organic compounds in fine particles. Anthropogenic radionuclides fingerprint characteristics in <0.053 mm samples were specially discussed. ²³⁶U/²³⁸U atom ratios were detected in the range of (0.627-3.38) × 10^-8. A weak correlation between anthropogenic ²³⁶U and natural U isotopes were observed. The intermediate correlation between ²³⁶U and ¹³⁷Cs indicated somewhat distinct migration behavior of these two radionuclides in soil after release to the environment. The released amount of ²³⁶U from global fallout during the period of atmospheric nuclear weapons testing was roughly estimated to be 1300 ± 448 kg. These results could be used as fingerprint information for anthropogenic ²³⁶U migration behavior and tracer application in environment.

CAESIUM RETENTION CHARACTERISTICS OF KNIFC-PAN RESIN FROM RIVER WATER

The caesium retention characteristics of a potassium-nickel hexacyanoferrate resin in a polyacrylnitrile (KNiFC-PAN) matrix were tested in fresh water over the range of 2.5-400 mL min-1. The experimental setup used 2 mL resin and 4-L aliquots of freshwater samples. The results showed nearly 100% retention at speeds below 10 mL min-1, above 80% up to 100 mL min-1, and approached 50% at 400 mL min-1. Using 100 mL min-1 flow rate and KNiFC-PAN resin in a well-type HPGe detector, the minimum detectable concentration was reduced to 3 mBq kg-1 for 4-L aliquots of water samples from the previous 15 mBq kg-1 achieved by Powdex ion-exchange resin and a planar type HPGe detector.

Assessment of chromosome aberrations in large Japanese field mice (Apodemus speciosus) in Namie Town, Fukushima

PURPOSE

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in Japan on March 11 2011, the surroundings became contaminated with radionuclides. To understand the possible biological effects after chronic low dose-rate radiation in contaminated areas of Fukushima, we assessed the effects in large Japanese field mice (Apodemus speciosus) by means of chromosome aberration analysis.

MATERIALS AND METHODS

We collected A. speciosus in five sites around Namie Town, Fukushima (contaminated areas) and in two sites in Hirosaki City, Aomori (control areas, 350 km north of FDNPP) from autumn 2011 to 2013. The number of mice captured and ambient dose-rates were as follows: high (n = 11, 10.1-30.0 µGy h^-1), moderate (n = 10, 5.7-15.6 µGy h^-1), low (n = 12, 0.23-1.14 µGy h^-1) and control (n = 20, 0.04-0.07 µGy h^-1). After spleen extraction from rodents, spleen cell culture was performed to obtain metaphase spreads. Chromosome aberrations were assessed on Giemsa-stained metaphase spreads.

RESULTS

Although the mice in the contaminated areas were chronically exposed, there was no radiation-specific chromosome aberrations observed, such as dicentric chromosomes and rings. Some structural aberrations such as gaps and breaks were observed, and these frequencies decreased annually in mice from Namie Town.

CONCLUSION

These findings suggest that chromosome aberration analysis is useful to evaluate and monitor radiation effects in wild animals.

THE IMPACT ON THE EYE LENS OF RADIATION EMITTED BY NATURAL RADIONUCLIDES (LEAD-210) PRESENT IN RADIATION PROTECTION GLASSES

Most radiation protection items made from modern lead contain 210Pb. This study estimated the impact on eye lens of radiation derived from the 210Pb in three types of radiation protection glasses. The counts from the glasses were measured using a Geiger-Müeller survey meter. The net count rate was 92 ± 1 cpm at a distance of 0.5 cm for one type of glasses. Additionally, we conducted a qualitative γ-ray spectrum analysis using a high-purity germanium semiconductor detector. The absorbed dose in the eye lens was related to 210Pb and its daughter radionuclide, 210Bi; this dose was calculated by applying dose conversion coefficients provided by the International Commission on Radiological Protection. The absorbed dose rate in eye lens was conservatively calculated to be on the order of 10 nGy/h for the type of glasses containing the most 210Pb. The dose from β-rays accounted for >99%. In addition, we investigated the dose-reduction effect using a thin acrylic plate. The count rate approximately decreased to background level by inserting a plate with a thickness of 1 mm. We conclude that the impact of 210Pb contained in radiation protection glasses is negligibly small, particularly considering the usefulness of the significant external exposure reduction.

Vertical distribution of 129I and radiocesium in forest soil collected near the Fukushima Daiichi Nuclear Power Plant boundary

Three soil core samples were collected from a forest located about 1.1 km south of the Fukushima Daiichi Nuclear Power Plant (FDNPP) boundary in 2017, and the vertical profiles of ¹²⁹I from the FDNPP accident were determined by the combination of TMAH (tetramethyl ammonium hydroxide) extraction and ICP-MS/MS analysis. The humus layer above the soil layer was heavily contaminated with ¹³⁴Cs (1983-5985 Bq g^-1) and ¹³⁷Cs (1947-5902 Bq g^-1) (decay-corrected to March 11, 2011). The ¹²⁹I activity concentrations decreased sharply with the soil depth, from 1894 to 34.1, from 9384 to 78.9, and from 2536 to 51.3 mBq kg^-1, for the three sites. Downward migration of ¹²⁹I was slightly faster than the one of ¹³⁴Cs. In addition, the cumulative ¹²⁹I inventories were observed to be 43.4 ± 1.0, 71.7 ± 1.8, and 56.5 ± 1.8 Bq m^-2, respectively. Subsequently, the cumulative ¹³¹I inventories were estimated to be 1.76 ± 0.06, 2.90 ± 0.11, and 2.28 ± 0.10 GBq m^-2 (decay-corrected to March 11, 2011), respectively. Finally, the total atmospheric deposition of ¹²⁹I on the land of Japan due to the FDNPP accident was estimated to be around 1.09-1.71 kg (7.11-11.2 GBq).

236U and radiocesium in river bank soil and river sediment in Fukushima Prefecture, after the Fukushima Daiichi Nuclear Power Plant accident

Almost 8 years after the Japanese Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, data for ²³⁶U and ²³⁶U/²³⁸U have mainly remained limited to only a few heavily contaminated samples. In the present study, activities of ²³⁶U, ¹³⁴Cs, and ¹³⁷Cs, along with ²³⁴U, ²³⁵U, ²³⁸U, in 15 river bank soil and 10 river sediment samples, were measured by ICP-MS/MS and γ spectrometry. The ¹³⁴Cs activities and ¹³⁴Cs/¹³⁷Cs activity ratios (decay-corrected to March 11, 2011) in these 15 river bank soil samples were from 74.8 to 3.88 × 10⁵ Bq kg^-1 and from 0.944 to 1.02, respectively; and in these 10 river sediment samples were from 87.1 to 1.86 × 10⁵ Bq kg^-1 and from 0.904 to 0.990, respectively. The ²³⁶U activities and ²³⁶U/²³⁸U atom ratios in these soil samples were in the respective ranges of (0.139-17.6) × 10^-5 Bq kg^-1 and (0.259-3.83) × 10^-8; and in these sediment samples were in the respective ranges of (0.884-27.0) × 10^-5 Bq kg^-1 and (1.12-5.04) × 10^-8. For one river sediment core sample, ¹³⁴Cs and ²³⁶U activities decreased with the depth indicating ¹³⁴Cs and ²³⁶U accumulated in the river sediment with time. Unlike ¹³⁴Cs, no clear evidence of FDNPP accident-derived ²³⁶U has been found in this study, although further monitoring is encouraged to establish the background database on ²³⁶U/²³⁸U for its potential application as a tracer in environmental studies.

Determination of the geographical origin of marine mussels (Mytilus spp.) using 143Nd/144Nd ratios

Geographical traceability of marine bivalves is critical to guarantee their quality and safeguard the interest of both consumers and producers. The neodymium isotopic ratio (¹⁴³Nd/¹⁴⁴Nd) of the coastal water mainly reflects the geology of its neighboring watershed, displaying the distinct and systematic variability at high level of geographical detail and thereby shedding light on its potential as a geochemical tracer. For the first time, the present study investigated the utility and robustness of ¹⁴³Nd/¹⁴⁴Nd archived in mytilid mussel shells for geographical traceability purposes. The reproducibility of ¹⁴³Nd/¹⁴⁴Nd ratios maintained in mussels shells from the same cohort demonstrates that the Nd isotopic ratio meets the major requirement for an ideal geochemical tracer, i.e., the biologically induced variation should be rather minimal. The distribution and variability of mussel shell ¹⁴³Nd/¹⁴⁴Nd patterns were subsequently mapped along the Japanese and Chinese coastal waters. Neodymium isotopes of mussel shells record ¹⁴³Nd/¹⁴⁴Nd variations among local regions and between the two countries, which are rather compatible with the ages and lithology of the continental bedrocks. These findings highlight the great potential of ¹⁴³Nd/¹⁴⁴Nd for tracing the geographical origin of marine bivalves.

First report on global fallout 236U and uranium atom ratios in soils from Hunan Province, China

More nuclear power plants continue to be built in China. Due to its long half-life, radiotoxicity and potential application as an environmental tracer, ²³⁶U is one of the most important artificial radionuclides deserving more study since activity data are important for risk assessment. However, the ultra-trace activity of ²³⁶U and its dilution by natural uranium isotopes make it difficult to distinguish its sources and there are only limited global fallout ²³⁶U data for present in Chinese environmental samples. In order to understand the background levels for uranium isotopes, especially ²³⁶U, and clarify their sources, inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) was applied to analyze uranium isotopes in 48 soil samples from Hunan Province, China. The ²³⁴U, ²³⁵U, ²³⁸U and ²³⁶U concentrations were measured as 9.91-33.7, 0.312-1.43, 6.63-28.7 Bq kg^-1 and (1.61-21.3) × 10⁷ atoms g^-1, while, the ²³⁶U/²³⁸U, ²³⁴U/²³⁸U and ²³⁵U/²³⁸U atom ratios were (0.470-4.91) × 10^-8, (5.10-9.31) × 10^-5, and (7.11-7.82) × 10^-3, respectively. The uranium isotopic fractionation may be due to irrigation of the agricultural lands where the samples were collected. Considering the facts that neither previous nuclear tests nor nuclear accidents had occurred in Hunan Province and the present ²³⁶U/²³⁸U atom ratios were included in the range of global fallout values in other areas, it may be concluded that ²³⁶U in soils from Hunan Province is mainly from global fallout. To the best of the authors' knowledge, the presence of global fallout ²³⁶U in soil samples from China has been confirmed for the first time, and these values may be useful as background data for risk assessment in the future.

A review of measurement methodologies and their applications to environmental 90Sr

The high fission yield product ⁹⁰Sr has been released into the environment in large amounts due to nuclear weapon tests, nuclear power plant accidents, and nuclear fuel reprocessing industries. It is a long half-life radionuclide (28.9 y), with serious consequences to human health; hence, it is desirable to perform routine monitoring of ⁹⁰Sr in environmental samples. Many ⁹⁰Sr radiometric methods have been developed in the past decades, which generally require complicated separation and purification steps with a relatively long analytical time. Moreover, some nominally rapid methods usually have high method detection limits, making them unsuitable for the environmental samples with ultra-low ⁹⁰Sr levels. In this review, some rapid and practical methods for ⁹⁰Sr routine monitoring are summarized. Different sample pretreatments and major purification procedures for ⁹⁰Sr developed in recent years, such as variable digestion methods and extraction chromatography using Sr resin or DGA resin, are especially described. Additionally, four conventional and widely used β spectrometric and mass spectrometric methods are demonstrated. Finally, ⁹⁰Sr evaluations focusing on contaminated soil and seawater samples collected after the Fukushima Daiichi Nuclear Power Plant accident, and ⁹⁰Sr application as tracers for environmental behavior are also reviewed.

Can 129I track 135Cs, 236U, 239Pu, and 240Pu apart from 131I in soil samples from Fukushima Prefecture, Japan?

In the present study, ¹²⁹I activities and ¹²⁹I/¹²⁷I atom ratios were measured in 60 soil samples contaminated by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. The ¹²⁷I concentrations, ¹²⁹I activities, and ¹²⁹I/¹²⁷I atom ratios in dry-weight were observed to be 0.121–23.6 mg kg⁻¹, 0.962–275 mBq kg⁻¹, and (0.215–79.3) × 10⁻⁷, respectively. The maximum values of both ¹²⁹I activities and ¹²⁹I/¹²⁷I atom ratios in Japanese soil increased about three orders of magnitude due to this accident. The equation logy = 0.877logx + 0.173 (Pearson’s r = 0.936; x, ¹²⁹I concentration; y, ¹³¹I concentration; decay-corrected to March 11, 2011) instead of a simple constant may be a better way to express the relationship between ¹²⁹I and ¹³¹I in Japanese soil affected by both global fallout and FDNPP accident fallout. In addition, a moderate correlation was observed between ¹²⁹I and ¹³⁵Cs (logy = 0.624logx + 1.01, Pearson’s r = 0.627; x, ¹²⁹I activity; y, ¹³⁵Cs activity). However, ¹²⁹I presented larger fractionations with less volatile radionuclides, such as ²³⁶U, ²³⁹Pu, and ²⁴⁰Pu. These findings indicated ¹³⁵Cs could be roughly estimated from ¹²⁹I or ¹³¹I; this is advantageous as fewer ¹³⁵Cs data are available and ¹³⁵Cs/¹³⁷Cs is being considered a promising tracer during radiocesium source identification.

Plutonium Isotopes (239-241Pu) Dissolved in Pacific Ocean Waters Detected by Accelerator Mass Spectrometry: No Effects of the Fukushima Accident Observed

The concentration of plutonium (Pu) and the isotopic ratios of ²⁴⁰Pu to ²³⁹Pu and ²⁴¹Pu to ²³⁹Pu were determined by accelerator mass spectrometry (AMS) in Pacific Ocean water samples (20 L each) collected in late 2012. The isotopic Pu ratios are important indicators of different contamination sources and were used to identify a possible release of Pu into the ocean by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. In particular, ²⁴¹Pu is a well-suited indicator for a recent entry of Pu because ²⁴¹Pu from fallout of nuclear weapon testings has already significantly decayed. A total of 10 ocean water samples were prepared at the Radiochemie München of the TUM and analyzed at the Vienna Environmental Research Laboratory (VERA). Several samples showed a slightly elevated ²⁴⁰Pu/²³⁹Pu ratio of up to 0.22 ± 0.02 compared to global fallout (²⁴⁰Pu/²³⁹Pu = 0.180 ± 0.007), whereas all measured ²⁴¹Pu-to-²³⁹Pu ratios were consistent with nuclear weapon fallout (²⁴¹Pu/²³⁹Pu < 2.4 × 10^-3), which means that no impact from the Fukushima accident was detected. From the average ²⁴¹Pu-to-²³⁹Pu ratio of 8_-2⁺³ ×10^-4 at a sampling station located at a distance of 39.6 km to FDNPP, the 1-σ upper limit for the FDNPP contribution to the ²³⁹Pu inventory in the water column was estimated to be 0.2%. Pu, with the signature of weapon-grade Pu was found in a single sample collected around 770 km off the west coast of the United States.

Determination of picomolar beryllium levels in seawater with inductively coupled plasma mass spectrometry following silica-gel preconcentration

A robust and rapid method for the determination of natural levels of beryllium (Be) in seawater was developed to facilitate mapping Be concentrations in the ocean. A solid-phase extraction method using a silica gel column was applied for preconcentration and purification of Be in seawater prior to determination of Be concentrations with inductively coupled plasma mass spectrometry (ICP-MS). Be was quantitatively adsorbed onto silica gel from solutions with pH values ranging from 6.3 to 9, including natural seawater. The chelating agent ethylenediamine tetraacetic acid was used to remove other ions in the seawater matrix (Na, Mg, and Ca) that interfere with the ICP-MS analysis. The reproducibility of the method was 3% based on triplicate analyses of natural seawater samples, and the detection limit was 0.4 pmol kg(-1) for 250 mL of seawater, which is sufficient for the analysis of seawater in the open ocean. The method was then used to determine the vertical profile of Be in the eastern North Pacific Ocean, which was found to be a recycled-type profile in which the Be concentration increased with depth from the surface (7.2 pmol kg(-1) at <200 m) to deep water (29.2 pmol kg(-1) from 3500 m to the bottom).

A method of measurement of (239)Pu, (240)Pu, (241)Pu in high U content marine sediments by sector field ICP-MS and its application to Fukushima sediment samples

An accurate and precise analytical method is highly needed for the determination of Pu isotopes in marine sediments for the long-term marine environment monitoring that is being done since the Fukushima Dai-ichi Nuclear Power Plant accident. The elimination of uranium from the sediment samples needs to be carefully checked. We established an analytical method based on anion-exchange chromatography and SF-ICP-MS in this work. A uranium decontamination factor of 2 × 10(6) was achieved, and the U concentrations in the final sample solutions were typically below 4 pg mL(-1), thus no extra correction of (238)U interferences from the Pu spectra was needed. The method was suitable for the analysis of (241)Pu in marine sediments using large sample amounts (>10 g). We validated the method by measuring marine sediment reference materials and our results agreed well with the certified and the literature values. Surface sediments and one sediment core sample collected after the nuclear accident were analyzed. The characterization of (241)Pu/(239)Pu atom ratios in the surface sediments and the vertical distribution of Pu isotopes showed that there was no detectable Pu contamination from the nuclear accident in the marine sediments collected 30 km off the plant site.

Concentration of (3)H in plants around Fukushima Dai-ichi Nuclear Power Station

A large amount of radionuclides was released from the Fukushima Dai-ichi Nuclear Power Station (FDNPS) following the damage caused by the tsunami due to the Great East Japan Earthquake on 11 March 2011. Although many radionuclides in various environmental samples around the FDNPS have been measured, (3)H in the terrestrial environment has not yet been reported. We present here the first survey results of (3)H concentrations in plant samples collected around the FDNPS in 2011 from shortly after the accident. The free-water (3)H concentrations in herbaceous plant shoots and evergreen tree leaves were considerably higher than the previous background concentration, and diminished with distance from the FDNPS. Although reconstruction of atmospheric (3)H concentrations after the accident is difficult, a rough estimate of the radiation dose due to (3)H inhalation about 20 km from the FDNPS is on the order of a few microsieverts (μSv).

Radioactive pollution from Fukushima Daiichi nuclear power plant in the terrestrial environment

Major contaminants from venting and hydrogen explosions at the Fukushima Daiichi nuclear reactors between 12 and 15 March 2011 were transported northwestward and deposited on soil and plants via precipitation. Surface soils and plant leaves were sampled at 64 sites in the Fukushima Prefecture. The highest concentrations of (134)Cs (84.4 kBq kg(-1)) and (137)Cs (82.0 kBq kg(-1)) in surface soils were observed at Nagadoro in Iidate village located 32 km northwest from the Fukushima Daiichi nuclear power plant. Furthermore, (131)I, (129)Te, (129 m)Te, (110 m)Ag and (140)La were detected in the same samples. Outer surface of plant leaves, such as bamboo, cabbage and grasses were highly contaminated at the high-dose rate areas of Tsushima and Minami-Tsushima in Namie town. Mugwort leaves that grew after the pollution event had extremely low concentration of radionuclides; however, the plant/soil radiocaesium ratio was 0.023 ± 0.006. It is anticipated that decomposition of fallen leaves will promote recycling of radionuclides in the environment.

Roles of short-chain fatty acids receptors, GPR41 and GPR43 on colonic functions

Short chain fatty acids (SCFAs) are the major anions in the large intestine. They are produced by a bacterial fermentation of dietary fiber. SCFAs are known to have a variety of physiological and pathphysiological effects on intestine. However, the mechanisms by which intraluminal SCFAs are sensed are not known. In 2003, two orphan G protein coupled receptors (GPRs), GPR41 and GPR43, have been cloned and demonstrated to be receptors for SCFAs. Thus, we had attempted to make antibodies raised against GPR43 and GPR41 to elucidate the roles of SCFAs on colonic functions. We have also evaluated the effects of SCFAs on colonic motility to define the physiological roles on luminal SCFAs. In rat and human colon, GPR43 protein was detected by Western blot analysis in extracts of whole wall and separated mucosa, but not in muscle plus submucosa extract. By immunohistochemistry, GPR43 immunoreactivity was localized with enteroendocrine cells expressing peptide YY, whereas 5-HT immunoreactive enteroendocrine cells were not immunoreactive for GPR43. GPR41 immunoreactivity was also found in human colon. In functional studies, propionate and butyrate concentration-dependently (10 microM - 10 mM) induced phasic and tonic contractions in rat colonic circular muscle. The propionate-induced phasic contraction was attenuated by atropine, tetrodotoxin and the 5-HT(4) receptor antagonists SB204070. However, acetate did not induce phasic or tonic contractions. Propionate-induced responses were not observed in mucosal free preparations. The present results suggest that the SCFA-induced physiological effects on colonic functions might be attributable to the activation of SCFA receptors on epithelial cells in the colon.