Spatiotemporal variations and environmental behavior of activity concentrations of natural and artificial radionuclides in soils of Fukuoka, Japan (1980-2019).

The activity concentration of natural and anthropogenic radionuclides in soil and rock, and in benthic algae, corals and oysters across the St. Martin's island of Bangladesh were investigated together with physicochemical parameters and texture of soil with an aim of evaluating the radioecology of the island. Soil and rock samples from the twenty-two locations of the island, eleven species of benthic algae, six species of corals and two species of oysters were analyzed. The activity of 226 Ra in soil was found in the range of 7.22–103.8, in benthic algae 2.5–9.7, in coral 5.5–10 and in oyster 4.2–11.5 Bq kg-1 . The activity of 232 Th in soil was found in the range of 14.56–216, in benthic algae 1.3–12.6, in coral 4.4–15.6 and in oyster 3.2–8.4 Bq kg-1 ; and the activity of 40 K in soil was in the range of 322–732, in benthic algae 17.1–45.5, in coral 21–146 and in oyster 24–32 Bq kg-1 . The external radiation dose rate due to activity concentration of natural radionuclides in soil was assessed. The activity of anthropogenic 137 Cs was found below detection limit.

The determination of the radioactivity of soils in settlements and natural territories is necessary to identify areas with an increased level of radionuclide content. The paper is devoted to studying the features of accumulation of natural radionuclides (226Ra, 232Th, 40K) and artificial 137Cs by plants in the conditions of semiarid steppes on the example of the chestnut zone of the Rostov region. Samples of soils and plants selected in the Tsimlyansky, Volgodonsky, Dubovsky and Orlovsky districts of the Rostov region during the 2014-2017 expeditions were used as objects of research. The activity concentration of radionuclides in soil and plants was measured by gamma spectrometric method of radionuclide analysis. It is shown that the distribution of artificial radionuclide 137Cs in the soil cover of the Rostov region, caused by the accident at the Chernobyl nuclear power plant, is extremely uneven and depends on the humus content. Biogenic element 40K accumulates in the surface horizon, also correlating with the humus content. The activity concentration of 137Cs content on 40K is most clearly displayed in the upper layer (0-10 cm). The lowest activity concentration of natural radionuclides is typical for alluvial-meadow soils and salt marshes of lightweight granulometric composition formed in floodplains of rivers and on coastal areas of lake Manych-Gudilo. In chestnut and dark-chestnut soils, the activity concentration of natural radionuclides is almost comparable, since variations in the activity concentration of these radionuclides in these soils are within the measurement error (10-15 %). The aggregated transfer factors from soil to plants for all radionuclides were generally less than 0.4 m2/kg. Variations in radionuclide aggregated transfer factors in the ecosystem are caused by climatic conditions during the selection period and, as a result, by mechanical contamination of soil particles and dust both during rains and during droughts, when the soil begins to dust.

Abstract. Topographic effects on Cs-137 concentrations in a forested area were quantitatively examined using 58 soil core samples collected in a village in Fukushima, Japan, which was directly impacted by the radioactive plume emitted during the 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. In this study, five topographic parameters and two soil properties were evaluated as controls on the soil Cs-137 concentration using generalized additive models (GAMs), a flexible statistical method for evaluating the functional dependencies of multiple parameters. GAMs employing soil dry bulk density, mass water content, and elevation explained 54 % of the observed concentrations of Cs-137 within this landscape, whereas GAMs employing elevation, slope, and upslope distance explained 47 % of the observed concentrations, which provide strong evidence of topographic effects on Cs-137 concentrations in soils. The model fit analysis confirmed that the topographic effects are strongest when multiple topographic parameters and soil properties are included. The ability of each topographic feature to predict Cs-137 concentrations was influenced by the resolution of the digital elevation models. The movement of Cs-137 into the subsurface in this area near Fukushima was faster in comparison to regions affected by the Chernobyl Nuclear Power Plant accident. These results suggest that the effects of topographic parameters should be considered carefully in the use of anthropogenic radionuclides as environmental tracers and in the assessment of current and future environmental risks due to nuclear power plant accidents.

Baseline levels of natural radioactivity in the bottom sediments of the East Siberian and Laptev Seas and assessment of the associated risks.

A first comprehensive study is presented on natural radionuclide activity concentrations in surface soils in different divisions of Tafila city. The natural radioactivity of 238U, 232Th and 40K is determined using gamma spectroscopy. The soil activity concentrations ranged from 1.8 to 76.4 Bq kg?1 for 238U, 6.3 to 85.5 Bq kg?1 for 232Th, and 84 to 516.7 Bq kg?1 for 40K. The activity concentrations of the radionuclide in soils are directly relevant to outdoor exposure. Absorbed dose rates in air outdoors were calculated to be in the range of 22.28 – 62.71 nGy h?1 with an overall average value of 40.12 nGy h?1. The study showed an annual effective dose equivalent in the range of 27.34 – 76.96 µSv y?1. A comparison of the measured values with the corresponding worldwide average values shows that the activities of natural radionuclides in the studied samples are below the world average activity values.

Since the accident at Fukushima Daiichi Nuclear Power Plant (FDNPP), concerns have arisen in Japan regarding the presence of radionuclides in food. Moreover, exposure levels to 90Sr and Pu isotopes in adults and those to 134Cs+137Cs, 90Sr, and Pu (where Cs, Sr, and Pu are cesium, strontium, and plutonium, respectively) in children have not been examined. Therefore, this study employed a duplicate portion approach to examine dietary exposure levels of radionuclides in adults and children following the FDNPP accident. The study spanned fiscal years 2012-2014 and was conducted in 10 prefectures: Hokkaido, Iwate, Miyagi, Fukushima, Ibaraki, Saitama, Tokyo, Kanagawa, Osaka, and Kochi. The participants provided portions of their meals for two non-consecutive days and completed questionnaires on the meal items. The activity concentrations of 134Cs, 137Cs, 90Sr, and 239+240Pu, which are targets of standard limits for radionuclides in foods in Japan, were determined according to the Radioactivity Measurement Series. The daily intake was calculated based on the radionuclide activity concentrations in the duplicate portion samples, and the committed effective doses were estimated using dose coefficients for the ingestion of each radionuclide provided by the International Commission on Radiological Protection. Approximately 80 duplicate samples were obtained in each fiscal year, and 242 samples were collected. The highest summed activity concentration of 134Cs and 137Cs was 11 Bq/kg, which was recorded in Date City (child) in 2013; this level was approximately one-ninth of the standard limit for general foods (100 Bq/kg). The committed effective dose from annual ingestion of the sample described above was 74 µSv, approximately 14 times lower than the maximum permissible level of 1 mSv/y. Pu was not detected and the 90Sr activity concentrations were similar to those before the FDNPP accident. For the samples examined in the present study, the 134Cs, 137Cs, 90Sr, and 239+240Pu dietary exposure levels were considerably lower than the regulatory levels and may not pose a health risk.

The surveys of natural gamma-emitting radionuclides and 137Cs in surface soils of coniferous forest sites in and around Izmir were conducted during 2003–2004. The soil samples were collected from three different depths of 15 forest sites, particularly local wild edible mushrooms areas. The average activity concentrations and ranges of the natural radionuclides in the soils were as follows: 30 (14–51) Bq kg−1 of 226Ra; 40 (17–79) Bq kg−1 of 232Th; and 581 (308–879) Bq kg−1 of 40K. Moreover, the values of 137Cs activity concentrations averaged over the depth sections varied from 20 to 82 Bq kg−1 with a mean value of 52 Bq kg−1. Accordingly, the levels of the studied natural radionuclides in the forest soils were within the range specified by UNSCEAR (2000) report for regular soils as well as the agricultural soils from the West Anatolia, while the measured activity levels of 137Cs in the forest soils were still high in contrast to agricultural soils after 16 years from the deposition of Chernobyl fallout.

137Cs and 90Sr in surface waters of the Sea of Japan: Variations and the Fukushima Dai-ichi Nuclear Power Plant accident impact

Linking heterogeneous distribution of radiocaesium in soils and pond sediments in the Fukushima Daiichi exclusion zone to mobility and potential bioavailability

Alteration of the Cesium-137 soil profile by wild boar rooting after the Fukushima Daiichi Nuclear Power Plant accident

We measured vertical distributions of radiocesium (134Cs and 137Cs) at stations along the 149°E meridian in the western North Pacific during winter 2012, about ten months after the Fukushima Dai-ichi Nuclear Power Plant (FNPP1) accident. The Fukushima-derived 134Cs activity concentration and water-column inventory were largest in the transition region between 35 and 40°N approximately due to the directed discharge of the contaminated water from the FNPP1. The bomb-derived 137Cs activity concentration just before the FNPP1 accident was derived from the excess 137Cs activity concentration relative to the 134Cs activity concentration. The water-column inventory of the bomb-derived 137Cs was largest in the subtropical region south of 35°N, which implies that the Fukushima-derived 134Cs will also be transported from the transition region to the subtropical region in the coming decades. Mean values of the water-column inventories decay-corrected for the Fukushima-derived 134Cs and the bomb-derived 137Cs were estimated to be 1020 ± 80 and 820 ± 120 Bq m−2, respectively, suggesting that in winter 2012 the impact of the FNPP1 accident in the western North Pacific Ocean was nearly the same as that of nuclear weapons testing. Relationship between the water-column inventory and the activity concentration in surface water for the radiocesium is essential information for future evaluation of the total amount of Fukushima-derived radiocesium released into the North Pacific Ocean.

The paper describes the trends of concentrations of 90Sr and 137Cs in milk in Lithuania in 1965–2003. Sampling of milk was performed in five regions of the biggest cities of Lithuania, and since 1976 ‐ also in the region of possible impact of Ignalina Nuclear Power Plant (NPP). Data of production and consumption of milk are taken from Lithuanian statistical yearbooks. Activity concentrations of radionuclides were measured at Radiation Protection Centre. Daily diet products are connected with different components of the environment ‐ soil, air and water. For this reason food contamination reflects pollution of the environment. This paper describes estimation of trends of activity concentrations of 90Sr and 137Cs in one of the food products ‐ in milk. Comparison applies to two periods ‐ the so‐called before Chernobyl period (1965–1985) and that after the accident in Chernobyl NPP up to now (1986–2003). Contamination of milk was analysed using correlation tests. Though the trend of average annual activity concentrations is complicated, during the two periods plenty of high enough correlation ratio values were calculated (0,63–0,74). Regression curves using 3–6 degree of polynoms show the decrease of 90Sr and 137Cs activity concentrations during the periods analysed. Factors of influence on the value of an average annual effective dose for an inhabitant of Lithuania based on activity concentrations of 90Sr and 137Cs in milk were evaluated. Estimation shows that accuracy of calculating an average annual effective dose due to 90Sr and 137Cs in milk does not exceed 60%.

Relationships between natural radionuclides activity concentration in soils of the State of Alagoas, Brazil and WRB/FAO soil classification, types of parental rocks and rainfall variability

Understanding the distribution and mobility of natural and artificial radionuclides in soil and river sediments is crucial for environmental monitoring and radiation risk assessment. This study investigates the vertical distribution of K-40, Ra-226, Th-232, and Cs-137 in the soils and river sediments of the Aragats Massif, Armenia, a region of interest for nuclear energy development. The research aims to establish baseline radionuclide levels, evaluate their mobility, and assess potential environmental implications. Soil and sediment samples were analyzed for radionuclide activity concentrations using gamma spectrometry with HPGe detector. Descriptive statistical methods and non-parametric tests were applied to assess distribution patterns and potential influencing factors. The results indicate that natural radionuclide activity concentrations in soils are consistent across different depths, suggesting a strong geogenic control over their distribution. Cs-137, primarily concentrated in the upper soil layers (0-10cm), exhibits limited vertical migration with a tenfold decrease in activity observed in deeper layers. Elemental concentrations of potassium, radium, and thorium were predominantly below global average values, and according to the geoaccumulation index of natural radionuclides, the surface soil of Aragats Massif is practically uncontaminated. River sediment analysis reveals higher natural radionuclide activity in fast-flowing mountain rivers, while Cs-137 activity remains below detectable levels near the Armenian Nuclear Power Plant, with the highest concentrations observed in high-altitude sediments, consistent with global radioactive fallout. These findings establish a baseline for future radioecological monitoring in the region, particularly in the context of potential nuclear energy developments in Armenia. The study provides insights into radionuclide behavior in soil and sediments, supporting regional environmental assessments and transboundary water resource management. Further investigations should focus on long-term monitoring and geochemical modeling to improve predictions of radionuclide mobility under changing environmental conditions.

The radioactivity of environmental samples from nuclear reactor sites must be analyzed before the public is given free access to the plants grown in these soils. Plant and corresponding soil samples were collected from a sample site around the Savar research reactor near Dhaka (Bangladesh) and the activity concentrations of natural radionuclides <sup>226</sup>Ra (<sup>238</sup>U-chain), <sup>228</sup>Ra (<sup>232</sup>Th-chain) and non-chained <sup>40</sup>K were measured using gamma ray spectrometry. Soils of Savar contained more radioactive <sup>40</sup>K than <sup>226</sup>Ra and <sup>228</sup>Ra. The influence of certain soil properties on the activity concentrations and transfer factors (TF) of natural radionuclides were investigated by correlating the observed data with those of soil properties. The activity concentrations of <sup>40</sup>K were much higher than those of <sup>226</sup>Ra and <sup>228</sup>Ra in plants due to higher uptake from soils. The transfer factors for <sup>226</sup>Ra, <sup>228</sup>Ra and <sup>40</sup>K were found to range from 0.04 to 0.10, 0.12 to 0.32, and 0.24 to 0.72, respectively. The soil to plant transfer factors for <sup>40</sup>K was found to be much higher in plants, which might be due to this element being vital in plants. This study showed that activity concentrations of these radionuclides in plants and their plant transfer factors seem to depend on the activity concentrations of the same radionuclides in soil.</p><p><strong> </strong>