Author Correction: A dataset of 137Cs activity concentration and inventory in forests contaminated by the Fukushima accident

A Correction to this paper has been published: https://doi.org/10.1038/s41597-021-00855-5.

Impact of typhoons on particulate and dissolved ¹³⁷Cs activities in seawater off the Fukushima Prefecture: results from the SOSO 5 Rivers cruise (October 2014)

Cruise SoSo 5 Rivers took place during October 2014 off the coast of Fukushima Prefecture shortly after the passage of two typhoons. Detection of dissolved 134Cs and 137Cs in all samples reflected contamination caused by accidental releases of radiocaesium from the Fukushima Dai-ichi Nuclear power plant (FNPP1) accident. The dissolved activities were generally higher at coastal sites and decreased with distance from shore, and they were higher in the surface than in the bottom water. The tendency of 137Cs activities to decrease with distance from the coast reflected mixing of coastal water and open-ocean water of which 137Cs activity concentration was ~1.5 Bq m−3. At stations very close to the coast, we observed high particulate 137Cs activity concentration that exceeded dissolved 137Cs activity concentration. 137Cs activities were generally 1–2 orders of magnitudes lower in organic particles than in dissolved form, and the ratios of 137Cs activity concentration in organic particles to 137Cs activity concentration in dissolved form ranged from 0.01 ± 0.00 to 0.12 ± 0.01. The ratio of 137Cs to 134Cs activity concentrations in organic particles did not change with distance from shore or with 137Cs activity concentration and generally remained around 1, even in samples collected far from the coast. This pattern indicated that the organic particles had come from rivers or a source very close to the coast. The 137Cs / 134Cs activity ratio in dissolved form north of FNPP1 region was estimated to be 1.074 ± 0.015, a ratio that is in good agreement with the 137Cs / 134Cs activity ratio in the core of Unit 1 of the FNPP1 while the 137Cs / 134Cs activity ratio at Tomioka port which located south of FNPP1 was 0.998 ± 0.017. Therefore we can conclude the source of radiocaesium in seawater in the coastal region north of FNPP1 was deposited radiocaesium released from the core of Unit 1 of FNPP1, while the source of radiocaesium observed in the coastal region south of FNPP1 was a mixture of deposited radiocaesium released from the core of Unit 2 and the core of Unit 1 of FNPP1. During September–October of each year, the typhoon season in Japan, the 137Cs activity concentration generally increased at Ukedo port, Tomioka port, FNPP1, and Iwasawa beach, and showed a good relationship with the 7-day modified antecedent precipitation index (API) while there is less correlation between the modified API and 137Cs activity concentration near the outlet of canal from unit 5 and 6 of FNPP1 to the sea.

Estimation of the Contribution of Dust Storm on April 16, 2020 to Radioactive Contamination of the Atmosphere During Forest Fires in the Exclusion Zone

On April 16, 2020, a strong dust storm was observed in the northern regions of Ukraine, which coincided with the period of intense wildland fires in the Chornobyl exclusion zone. The activity of 137Cs in aerosol particles released into the atmosphere as a result of resuspension from burned areas in the meadow biocenoses in the exclusion zone is evaluated in the article. Resuspension of radioactively contaminated particles from burned areas formed after fires in meadow biocenoses of the exclusion zone can be a powerful source of air contamination in the zone itself, as well as increase of the radionuclides transport outside it. The total 137Cs activity that entered the atmosphere during the dust storm was estimated to be about 162 GBq, i. e. up to 20% of the total activity emitted in the air during the entire period of forest fires on April 3–20, 2020. The 137Cs emission from burned areas during the dust storm on April 16 and 17 amounted to 0.24% of the total stock of 137Cs activity in this territory. According to the results of modeling, the relative contribution of wildland fires and resuspension due to the dust storm on April 16 and 17 significantly depends on the distance to the emission sources. It was found that the resuspension of radioactive particles from burned areas during the dust storm determined 80–95% of the 137Cs activity concentration in the surface air near Chornobyl nuclear power plant and in Chornobyl city and the rest was due to the continuing forest fires in neighboring territories. The maximum 3-hour averaged value of the 137Cs activity concentration in the air due to resuspension from the burned areas was obtained for the location of the monitoring post VRP-750 of SSE “Ecocenter” to be about 28 mBq/m3 for the period 9–12 hours on April 16. In Kyiv, the 3-hour averaged 137Cs activity concentration due to the dust storm in the Exclusion Zone was calculated as 44 μBq/m3 in the period from 9 to 12 hours on April 17, 2020. This value was only about 4% of the total 137Cs activity in the air in this period.

137Cs activity concentration in mushrooms from the Bobrůvka river valley

In the 2017-2018 mushrooming seasons at the (Bohemian-Moravian Highlands near Dolní­ Roží­nka) a total of 505 mushrooms belonging to 9 species were collected, and analyzed by gamma spectrometry for 137Cs activity. The maximum 137Cs activity of 575 Bq.kg-1 was detected in Boletus edulis species, what in native state, is just below the allowed limit. In contrast, in mushroom Imleria badia, which is reported to be associated with the highest cumulative capability from all fungi species, detected activity level was only 316 Bq. kg-1. However, differences in mean contamination values were not significant due to high variability. It was shown, that activity concentration is not dependent on the weight (size) of Imleria badia. Our results also confirmed generally well known lower 137Cs activity in the Russula species representatives belonging to the group of gills or lamella bearing mushrooms.

Long range transport of radiocaesium derived from global fallout and the Fukushima accident in the ocean interior of the Pacific Ocean since 1960s through 2017

<p>The world's oceans act as a sink for artificial radionuclides as well as for other anthropogenic pollutants released into the environment. Owing to physical and biogeochemical processes in the ocean, artificial radionuclides in the ocean are redistributed from their initial entry points which depend on the various sources. Long range transport of radiocaesium in the ocean interior were investigated and presented. Radiocaesium were derived from global fallout which occurred mainly late 1950s and early 1960s and the Fukushima accident occurred in 2011. In the ocean interior, main factor is subduction of mode water formation from surface to two mode waters, STMW and CMW. Radiocaesium then stayed long in both STMW and CMW, but relatively first recirculation and southward movement were observed in STMW for decadal time scale.</p><p>We establish database for artificial Radionuclides in the marine environment as HAM global 2018, doi: 10.34355/CRiED.U.Tsukuba.00001, and we reconstruct 137Cs activity concentration sections for 1965-1968 and 1970-1973 to understand initial conditions of 137Cs activity concentration in ocean interior just after large atmospheric fallout in early 1960s and 5 years after injection. We also carried out observations at stations between 49 deg. N and 60 deg. S along 165 deg.  E in 2002, 2012 and 2015. After that, we also observed vertical profiles in the western North Pacific Ocean.　</p><p>Basic feature of radiocaesium distribution along 165 deg. E section in 1963-1965 was dome shape distribution of which deepest places were around 30-40 deg. N and of which maximum depth were around 600- 800 meter depths. The penetration of 137Cs is found less than 800 m depth, associated with the bowl shape of isopycnals in the midlatitude region. In general, the 137Cs activity concentrations in the subsurface and intermediate water of the mid latitude region of the western North Pacific were higher than those in surface waters of the subtropical and equatorial Pacific. In 2002, we observed two 137Cs activity concentration maxima at 250 m and at 400 to 500 m depth at around 20 deg. N. The 137Cs activity concentration at the core at 400 to 500 m depth in 2002 was around 2 – 3 Bq m-3 and the start of moving in 1963-1965 was 16 Bq m-3 which indicates only one thirds of dilution occurred during about 40 years travel in the ocean interior as CMW. In 2012, we also observed two 134Cs activity concentration maxima at 150 m, 30 deg. N and at 300 m depth at 40N, while we observed a Fukushima derived at 300 m, 30 deg. N with southward movements. Basic feature of 137Cs distribution derived from atmospheric weapons test along 165 deg. E section in 2012 still keep dome shape distribution of which deepest places were around 30-35 deg. N and of which maximum depth were around 400 meters depths, while deepest places were around 20-30 deg. N in 2015. These findings strongly suggest that radiocaesium has been transporting in the ocean interior by subduction of mode waters from subarctic region to subtropical region and tropical region.</p>

Modeling Study of the Atmospheric Transport of Radioactivity Released into the Air as a Result of Forest Fires in the Exclusion Zone in April 2020

In April 2020, the largest forest fire occurred in the Chornobyl Exclusion zone in its history. The results of modeling the atmospheric transport of radioactive aerosols raised into the atmosphere as a result of fires in forest and grass areas in the Exclusion zone, as well as in radioactively contaminated forests outside it in Kyiv and Zhytomyr regions are presented in the paper. To assess the consequences of forest fires, a set of models of lifting, atmospheric transport and deposition of radionuclides on the underlying surface LEDI, developed at the Institute for Safety Problems of Nuclear Power Plants of the National Academy of Sciences of Ukraine, was used. Calculations of the dynamics of the 137Cs activity concentration field in the surface air on a regional scale (in Ukraine) and on a local scale (within the Exclusion zone) were performed. According to the simulation results, the maximum values of the 137Cs activity in the surface air of Kyiv in some periods during April 4−20 could reach 2−4 mBq/m3, and the integral value of 137Cs activity in the air of Kyiv for the whole period was about 450 mBq⋅s/m3. The obtained results are generally consistent with the data of measurements of radioactive contamination of the nearground air in Kyiv and areas of the nuclear power plants in Ukraine. The analysis of the consistency of the simulation results with the data of measurements of the 137Cs activity concentration in the air in the Exclusion zone was performed. The main ways to improve the methodology for assessing the consequences of forest fires by modeling the atmospheric transport of radionuclides are identified.

Temporal trends of ¹³⁷Cs activity concentration in pond waters in the vicinity of Fukushima Dai-ichi nuclear power plant

Closed and semi-closed water bodies, such as lakes and ponds, are important water resources in Fukushima area and they are the most sensitive environments to radioactive contamination after the Fukushima Dai-ichi nuclear power plant accident. Wakiyama et al. (2017) investigated 137Cs activity in water and bottom sediment in four ponds; Suzuuchi (SU), Funasawa (FS), Inkyozaka (IZ), and Kashiramori (KM), within 10 km zone from the FDNPP during 2015–2016. This study follows up their observation to address longer time trends of 137Cs activity concentration in pond waters and to show speciation of 137Cs in soil and bottom sediment. Mean total 137Cs activity concentration in water ranged from 2.5 to 29 Bq L−1. There was not found steady trend in the activity concentration of total and particulate 137Cs for four ponds. The concentration of dissolved 137Cs was usually low in winter during the entire observation period in all four ponds. A tendency to a decrease in the 137Cs activity concentration in suspended sediments was found for four ponds and the decreasing rate constants, including radiological decay, on SU, FS, IZ and KM were 0.33, 0.53, 0.29 and 0.25 yr−1, respectively. The results of sequential extractions of soil and bottom sediment samples showed higher proportion of bioavailable 137Cs, i.e., exchangeable and organic bound 137Cs, in bottom sediment than in the soil.