Examining the effects of soil entrainment during nuclear cloud rise on fallout predictions using a multiscale atmospheric modeling framework

Current operational models for nuclear cloud rise over land were developed and validated using observations from shallow-buried or surface detonations, where lofted soil quickly mixed with fission products from the detonation. These models poorly predict fallout from elevated detonations near the fallout-free height of burst (FFHOB), where interactions with the ground are limited and the mixing of fission products and lofted soil is incomplete. Fallout-free is a misnomer at this HOB, as fallout was observed in these cases, but was below the levels of concern, especially off-grounds of the nuclear test site. To correctly characterize and model fallout from detonations near the FFHOB, models must be developed which can capture the stratified nature of the particle and activity-size distributions within the cloud. Previously, it was shown that the Weather Research and Forecasting (WRF) model can accurately simulate nuclear cloud rise for airbursts with little to no ground interactions (Arthur et al., 2021). That work is expanded here by (1) using a radiation-hydrodynamics code to improve the fireball initialization in WRF, (2) further developing an aerosol package from WRF-Chem to simulate lofted soil, and (3) combining the WRF cloud rise simulations with the operational models used at the National Atmospheric Release Advisory Center (NARAC) for fallout modeling. Using this combination of codes, the Upshot-Knothole Grable detonation, which was just below the FFHOB, is simulated from seconds after detonation through cloud rise and fallout, and results are compared to historical test data. The results show improved prediction of dose rate and highlight the need to correctly characterize the entrainment of material into the cloud and the subsequent mixing of fission products with entrained material.

Ontogenetic exposure to light influences seabird vulnerability to light pollution

Light pollution critically affects fledglings of burrow-nesting seabirds, leading to massive mortality events. A successful management of this pollutant depends upon a comprehensive understanding of the factors influencing visual sensitivity and corresponding behaviours towards light. Factors shaping the development of the visual system could account for variation in seabirds' vulnerability to light pollution. We investigated how Cory's shearwater chicks respond to selected contrasting artificial light stimuli. Chicks were subjected to blue and red light treatments, and repeatedly tested throughout the nestling period. We analysed behavioural responses (number, timing, and orientation of reactions) to determine how age, exposure to experimental light stimuli, and spectra influenced the onset of visually guided behaviours, thus inferring drivers of vulnerability to light pollution. Repetitive exposure to light significantly increased the number of reactions, and chicks predominantly displayed light avoidance behaviour. We did not find differences in the number of reactions, timing and orientation between blue and red light treatments. The responses did not differ across different age groups. These results provide empirical evidence for the contribution of the light available in the rearing environment to seabird visual development. They support the hypothesis that differential exposure to light during the growth period influences responses to artificial light, and that the state of visual development at fledging could be a main driver of the age bias observed during seabird fallout events. It is thus important to evaluate lighting schemes at both urban and natural areas, and the yet unknown consequences already affecting the populations.

Radiation and leukaemia: Which leukaemias and what doses?

The cause(s) of most cases of leukaemia is unknown. Save for several rare inherited disorders the most convincingly-identified causes of leukaemia are exposures to ionizing radiations, to some chemicals and to some anti-cancer drugs. Data implicating ionizing radiations as a cause of leukaemias come from several sources including persons exposed to the atomic bomb explosions in Japan, persons receiving radiation therapy for cancer and other disorders, persons occupationally exposed to radiation such as radiologists and nuclear facility workers, cigarette smokers, and others. Although ionizing radiations can be a cause of almost all types of leukaemias, some are especially sensitive to induction such as acute and chronic myeloid leukaemias (AML and CML) and acute lymphoblastic leukaemia (ALL). Whether chronic lymphocytic leukaemia can be caused by radiation exposure is controversial. The mechanism(s) by which ionizing radiations cause leukaemia differs for different leukaemia types. I discuss these issues and close with a hypothesis which might explain why haematopoietic stem cells are localized to the bone marrow.

Be-7 and Pb-210 in fallout and aerosols in 2000-2016 in central Europe - Deposition velocity and dependence on meteorological parameters

The main aim of this research was to determine the transport and deposition velocities of ⁷Be and ²¹⁰Pb based on a vast database containing the results of measurements of ⁷Be and ²¹⁰Pb in fallout and aerosol samples carried out at several stations located throughout Poland in the period from 2000 to 2016. The monthly deposition flux of ⁷Be and ²¹⁰Pb showed an unequivocal downward trend but was also subject to seasonal changes, with maximum values in the summer period. The same patterns were found in the case of the deposition rate, the average values of which were 0.7 cm s^-1 for ⁷Be and 0.5 cm s^-1 for ²¹⁰Pb. A strong, statistically significant dependence of the deposition rate on the amount of dust was demonstrated, whereby a 10 μg m^-3 decrease in dust increases the ⁷Be deposition rate by 0.1 cm s^-1. Reduction of the concentration of carrier particles reduces the share of dry deposition in favour of precipitation convection, which is much more significant for the transport of both isotopes to the surface. Study of the effect of meteorological parameters showed that the concentrations of ⁷Be in fallout and aerosol samples and ²¹⁰Pb in fallout increase with increasing temperature, indicating a significant share of convection processes in isotope transport. The concentrations of ²¹⁰Pb in aerosols did not show any significant statistical changes over time. Their maximum values were observed in the winter period, indicating an additional source of this isotope related to combustion processes in the heating season. The studies confirmed the dominant role of convective precipitation and large-scale precipitation processes in the elution of ⁷Be from the atmosphere by showing the monthly deposition of this isotope to be strongly dependent on the total precipitation (r = 0.618).

Distribution of 137Cs and 85Sr in selected Egyptian plants after foliar contamination

The transfer of ¹³⁷Cs and ⁸⁵Sr from fallout to plants was studied in two successive pot experiments. Five plant species (Oryza Sativa, Tritichum Vulgares, Vicia Faba, Sesamum Orientale and Trifolium Alexandrinum) were grown in pots containing sandy clay loam soil. For simulating foliar contamination, radioactive ¹³⁷Cs and ⁸⁵Sr solutions were sprayed once with different activity concentrations gently on the shooting system. After 8 weeks of radioactivity application to the above first four plants and 4 weeks to the last one, the total absorption of ¹³⁷Cs and ⁸⁵Sr and their distribution in different parts of the tested plants were determined. Most of the absorbed ¹³⁷Cs and ⁸⁵Sr accumulated in shoots with proportions ranged from 70.8 to 81.9% and from 88.9 to 95.0%, respectively for different plants. The absorbed ¹³⁷Cs and ⁸⁵Sr by grains/seeds followed that of shoots with values ranged from 11.9 to 19.2% and from 5 to 10.9%, respectively. The percentage of ¹³⁷Cs absorbed by roots ranged from 6.2 to 10.0% among different plants, while ⁸⁵Sr in roots of plants was below the minimum detectable activity of the detector. For Trifolium, most of the absorbed ¹³⁷Cs and ⁸⁵Sr accumulated in the first harvest (81.9 and 98.6%). The aggregated transfer factors (T_ag) of both radionuclides under foliar conditions were to a great extent similar. The average values of T_ag factors (m²kg^-1) of ¹³⁷Cs and ⁸⁵Sr, respectively, in rice grains were 3.4 × 10^-4 and 1.6 × 10^-4; in wheat grains were 4.2 × 10^-4 and 2.1 × 10^-4; in bean seeds were 4.9 × 10^-4 and 2.6 × 10^-4; and in sesame seeds were 2.8 × 10^-4 and 1.2 × 10^-4. Those T_ag factors of grains/seeds were substantially lower than those obtained with straw of the corresponding plant species.

Distribution and settling behavior of americium-241 in the tropical East Pacific

The distribution of the anthropogenic radionuclide ²⁴¹Am, a decay product of ²⁴¹Pu discharged from atmospheric tests of nuclear weapons, was investigated to resolve its horizontal and vertical migration in the Tropical East Pacific. We analyzed ²⁴¹Am concentrations in seawater samples collected in 2003. On comparing the ²⁴¹Am concentrations with the previously determined concentrations of ^239+240Pu in the same samples, the vertical profiles of ²⁴¹Am were found to be similar to those of ^239+240Pu. At some stations, the maximum concentration of ²⁴¹Am occurred 100-200 m deeper than that of ^239+240Pu. The ²⁴¹Am/^239+240Pu ratios in the North Pacific and South Pacific were comparable to one another, and were the typical ratio for the Pacific. The ²⁴¹Am distribution was influenced by the water mass at depths below 400 m. The ²⁴¹Am data support the view there is a current flowing at depths of 400-3000 m from the North Pacific through the Equator to the South Pacific. In addition, the ²⁴¹Am vertical profile was explained by using a 1-D scavenging model that considers the decay of ²⁴¹Pu and adsorption and scavenging by suspended particles. The different depths for the maximum concentrations of ²⁴¹Am and ^239+240Pu observed at some stations were well explained by the model and by the distribution of CaCO₃ particles. The residence time of ²⁴¹Am in the Pacific was also estimated by using the model.

First study of 237Np in Chinese soils: Source, distribution and mobility in comparison with plutonium isotopes

In this study, the distribution and migration of ²³⁷Np and ^239+240Pu in soils in the vicinity (<5 km) of Qinshan and Tianwan Nuclear Power Plants in China were studied, which is the first specific study of global fallout ²³⁷Np in Chinese soils. The ²³⁷Np and ^239+240Pu concentrations in surface soils showed large spatial inhomogeneity. A remarkable ^239+240Pu concentration (4.783 mBq/g) was observed in a surface soil near Qinshan NPP and stands for the ever reported highest value in the Chinese soils. The inventories of ^239+240Pu in two Qinshan and Tianwan soil cores were estimated to be 128.8 Bq/m² and 121.0 Bq/m², respectively; while the ²³⁷Np inventories were 0.039 Bq/m² and 0.035 Bq/m² at these sites, respectively. The ²⁴⁰Pu/²³⁹Pu atomic ratios in these soils indicated that the global fallout is the main source of Pu in these regions. However, the non-isotopic ²³⁷Np/²³⁹Pu atomic ratio in environmental soil is not a sensitive indicator for source identification. Furthermore, we conducted pilot study on the migration behaviors of ²³⁷Np and ^239+240Pu in soil core at Qinshan site with the Convection-Dispersion Equation (CDE) model. The obtained apparent dispersion coefficients of ²³⁷Np (2.82 ± 2.06 cm²/y) was 5 times higher than that of ^239+240Pu (0.57 ± 0.16 cm²/y), proving that ²³⁷Np has stronger migration ability than Pu isotopes in the Qinshan soil. Finally, we predicted that with the increase of migration time, both ²³⁷Np and ^239+240Pu concentration in the soil will gradually become more evenly distributed among different soil layers due to the dominant dispersion effects.

Black rain in Hiroshima: a critique to the Life Span Study of A-bomb survivors, basis of the linear no-threshold model

Ionizing radiation is regulated by the linear no-threshold model (LNT), which asserts that the lowest doses of ionizing radiation are hazardous in proportion to the dose and dose rate. LNT is based on the data of the Life Span Study (LSS) of A-bomb survivors in Hiroshima and Nagasaki. Radiation doses of the survivors were estimated by using initial radiation (5% of blast energy) and residual radiation (10%) was neglected. The major component of residual radiation was fallout, most of which must be brought down to the ground by black rain. The rain was highly radioactive. There are three major black rain maps reporting that black rain covered wide areas of Hiroshima-City. The three lead to an important conclusion that not only A-bomb survivors but also not-in-the-city control subjects (NIC) were irradiated with residual radiation to a greater or lesser degree. This means that exposure doses in LSS were largely underestimated and that use of NIC as the negative control is faulty. Thus, LNT based on LSS is invalid. In addition, LSS ignores radiation hormesis ─ ionizing radiation is not always hazardous, but beneficial depending on doses and dose rates. Indeed, when LSS data of longevity were examined, a clear J-shaped dose-response, a hallmark of radiation hormesis, is apparent. Also, cancer mortality ratios are in the increasing order: NIC (exposed to residual radiation), A-bomb survivors (exposed to both initial and residual radiations), and the Japanese in general (no exposure). Thus, low dose radiation (LDR) is hormetic. Obstinate application of invalid LNT to regulation-unnecessary LDR has been causing tremendous human, social, and economic losses in Fukushima. Also, LNT prevents clinical application of radiation hormesis to age-associated diseases such as Alzheimer's disease and cancers.

Long-range transport of radiocaesium derived from global fallout and the Fukushima accident in the Pacific Ocean since 1953 through 2017-Part I: Source term and surface transport

Long range transport of radiocaesium derived from local fallout occurred early 1950s, global fallout which occurred mainly late 1950s and early 1960s and the Fukushima accident occurred in 2011 were investigated and presented for ocean surface in the Pacific Ocean. HAM database and its update were used in this study to present whole history of radioccaesium transport in surface layer in the interested region. Since both the main local/global fallout regions and injection of radiocaesium by Fukushima accident occurred in the western North Pacific and constrain of surface current systems which governed surface transport processes were subtropical gyre and subarctic gyre, radiocaesium transport in surface water in the mid latitude was characterized as rapid eastward transport along Kuroshio and Kuroshio extension. Behaviors were similar and repeated for local/global fallout and Fukushima derived radiocaesium. A part of radiocaesium transported/deposited/injected in the mid latitude subducted into ocean interior and the radiocaesium activity concentrations were kept higher rather than those in surface water.

Review of current nuclear fallout codes

The importance of developing a robust nuclear forensics program to combat the illicit use of nuclear material that may be used as an improvised nuclear device is widely accepted. In order to decrease the threat to public safety and improve governmental response, government agencies have developed fallout-analysis codes to predict the fallout particle size, dose, and dispersion and dispersion following a detonation. This paper will review the different codes that have been developed for predicting fallout from both chemical and nuclear weapons. This will decrease the response time required for the government to respond to the event.

Derivation and validation of a novel Semi Empirical Deposition Estimation Model (SEDEM)

Predictive models are necessary in order to minimize potential damages in the event of a nuclear or radiological release. For this reason, a novel model for the calculation of both wet and dry deposition from airborne radioactivity is proposed. Full derivation of the model and the estimation of uncertainty are presented, and the validity of the model is evaluated by calculating deposition based on several measured airborne activities in different countries. The results are compared with the corresponding measured deposition activities and the predictive power of the model is found to be good, i.e. calculated depositions being within the limits of measurement uncertainty. Additionally, limitations of the model and possible sources of error in the calculations are discussed.

High-resolution radiation mapping to investigate FDNPP derived contaminant migration

As of March 2016, five years will have passed since the earthquake and ensuing tsunami that crippled the Fukushima Daiichi Nuclear Power Plant on Japan's eastern coast, resulting in the explosive release of significant quantities of radioactive material. Over this period, significant time and resource has been expended on both the study of the contamination as well as its remediation from the affected environments. Presented in this work is a high-spatial resolution foot-based radiation mapping study using gamma-spectrometry at a site in the contaminated Iitate Village; conducted at different times, seventeen months apart. The specific site selected for this work was one in which consistent uniform agriculture was observed across its entire extent. From these surveys, obtained from along the main northwest trending line of the fallout plume, it was possible to determine the rate of reduction in the levels of contamination around the site attributable to the natural decay of the radiocesium, remediation efforts or material transport. Results from the work suggest that neither the natural decay of radiocesium nor its downward migration through the soil horizons were responsible for the decline in measured activity levels across the site, with the mobilisation of contaminant species likely adhered to soil particulate and the subsequent fluvial transport responsible for the measurable reduction in activity. This transport of contaminant via fluvial methods has already well studied implications for the input of contaminant material entering the neighbouring Pacific Ocean, as well as the deposition of material along rivers within previously decontaminated areas.

Temporal variability of beryllium-7 fallout in southwest UK

Cosmogenic beryllium-7 has been widely employed as a sediment tracing tool and continued development of its use as a soil erosion tracer requires knowledge of fallout temporal dynamics. Data regarding beryllium-7 fallout in the UK are scarce and here the authors provide a record of beryllium-7 fallout in southwest England spanning a two-year period. A monthly fallout record was developed for Plymouth, UK using regular rainfall sampling to determine beryllium-7 rainfall activity concentration (Bq L(-1)) and deposition flux (Bq m(-2)). Data showed a general tendency for higher activity during the spring/summer months and lower activity in the autumn/winter months. Comparison with data for other UK sites (Chilton and Aberporth) for the same period found significant differences in (7)Be activity in rainwater and lower variability in Plymouth than Chilton and Aberporth. Total deposition was largely controlled by rainfall in Plymouth although regression coefficients suggested greater importance of other atmospheric controls at the Chilton and Aberporth sites. Use of a deposition proportion to rainfall proportion ratio identified periods when deposition was influenced by varying (7)Be activity in rainfall. Broad ranges in ratios were found for Chilton and Aberporth and this has implications for sediment tracer studies requiring estimates of (7)Be deposition flux across months or seasons.

Measurement of fallout radionuclides, (239)(,240)Pu and (137)Cs, in soil and creek sediment: Sydney Basin, Australia

Soil and sediment samples from the Sydney basin were measured to ascertain fallout radionuclide activity concentrations and atom ratios. Caesium-137 ((137)Cs) was measured using gamma spectroscopy, and plutonium isotopes ((239)Pu and (240)Pu) were quantified using accelerator mass spectrometry (AMS). Fallout radionuclide activity concentrations were variable ranging from 0.6 to 26.1 Bq/kg for (137)Cs and 0.02-0.52 Bq/kg for (239+240)Pu. Radionuclides in creek sediment samples were an order of magnitude lower than in soils. (137)Cs and (239+240)Pu activity concentration in soils were well correlated (r(2) = 0.80) although some deviation was observed in samples collected at higher elevations. Soil ratios of (137)Cs/(239+240)Pu (decay corrected to 1/1/2014) ranged from 11.5 to 52.1 (average = 37.0 ± 12.4) and showed more variability than previous studies. (240)Pu/(239)Pu atom ratios ranged from 0.117 to 0.165 with an average of 0.146 (±0.013) and an error weighted mean of 0.138 (±0.001). These ratios are lower than a previously reported ratio for Sydney, and lower than the global average. However, these ratios are similar to those reported for other sites within Australia that are located away from former weapons testing sites and indicate that atom ratio measurements from other parts of the world are unlikely to be applicable to the Australian context.

Assessment of palladium footprint from road traffic in two highway environments

Palladium (Pd) is an emerging eco-toxic pollutant from vehicle catalytic converters, emitted worldwide for more than two decades. Nowadays, the spatial extent of Pd fallout is growing along roads, but its subsequent fate in neighboring terrestrial ecosystems has not been extensively addressed yet. Two sites representative of contrasted natural environments (field, forest) but located under similar ambient conditions were selected to isolate and analyze the specific impact of vehicular Pd, along highway A71, France. Pd impregnation was assessed along 200-m-long transects perpendicular to the highway. Contents were measured in soils, earthworms, plant communities of the right of way (ROW), and the neighboring field (crop weeds), as well as in a moss, and bramble and ivy leaves in the forest. The direct impact of Pd fallouts appears to be confined in the grassy verge of the highway: ROW soils ([Pd] = 52-65 ng g(-1)), earthworms ([Pd] = 18-38 ng g(-1)), and plant community ([Pd] = 10-23 ng g(-1)). Pd footprint is pointed out by the accumulation index calculated for earthworms and plant communities even though transfer coefficients indicate the absence of bioaccumulation (TCs < 1). An indirect longer range transfer of Pd is identified, induced by hydric transport of organic matter.

Global deposition and transport efficiencies of radioactive species with respect to modelling credibility after Fukushima (Japan, 2011)

In this study we conduct a detailed comparison of the modelling response of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident with global and local observations. We use five different model versions characterized by different horizontal and vertical resolutions of the same General Circulation Model (GCM). Transport efficiencies of (137)Cs across the world are presented as an indication of the expected radioactive impact. Activity concentrations were well represented showing lower Normalized Mean Biases (NMBs) when the better resolved versions of the GCM were used. About 95% of the results using the zoom configuration over Europe (zEur) remained within a factor of 10 from the observations. Close to Japan, the model reproduced well (137)Cs concentrations using the zoom version over Asia (zAsia) showing high correlations, while more than 64% of the modelling results were found within a factor of two from the observations and more than 92% within a factor of 10. Labile and refractory rare radionuclides calculated indirectly showed larger deviations, with about 60% of the simulated concentrations within a factor of 10 from the observations. We estimate that around 23% of the released (137)Cs remained into Japan, while 76% deposited in the oceans. Around 163 TBq deposited over North America, among which 95 TBq over USA, 40 TBq over Canada and 5 TBq over Greenland). About 14 TBq deposited over Europe (mostly in the European part of Russia, Sweden and Norway) and 47 TBq over Asia (mostly in the Asian part of Russia, Philippines and South Korea), while traces were observed over Africa, Oceania and Antarctica. Since the radioactive plume followed a northward direction before its arrival to USA and then to Europe, a significant amount of about 69 TBq deposited in the Arctic, as well. These patterns of deposition are fully consistent with the most recent reports for the accident.

New isotopic evidence of lead contamination in wheat grain from atmospheric fallout

Crops could accumulate trace metals by soil-root transfer and foliar uptake from atmospheric fallout, and an accurate assessment of pollution sources is a prerequisite for preventing heavy metal pollution in agricultural products. In this study, we examined Pb isotope rates to trace the sources of Pb in wheat grain grown in suburbs. Results showed that, even in zones with scarcely any air pollution spots, atmospheric fallout was still a considerable source of Pb accumulation in wheat. The concentration of Pb in wheat grain has poor correlation with that in farm soil. The Pb concentration in wheat grains with dust in bran coat was significantly higher than that in wheat grains, which indicates that Pb may accumulate by foliar uptake. The Pb isotope rate has obvious differences between the soil and atmospheric fallout, and scatter ratio is significantly closer between the wheat grain and atmospheric fallout. Atmospheric fallout is a more significant source of Pb concentration in wheat grains than in soil. As far as we know, this is the first study on the main sources of lead in grain crop (wheat) samples with isotope. This study aims to improve our understanding of the translocation of foliar-absorbed metals to nonexposed parts of plants.

Radiocaesium activity concentrations in parmelioid lichens within a 60 km radius of the Fukushima Dai-ichi Nuclear Power Plant

Radiocaesium activity concentrations ((134)Cs and (137)Cs) were measured in parmelioid lichens collected within the Fukushima Prefecture approximately 2 y after the Fukushima Dai-ichi Nuclear Power Plant accident. A total of 44 samples consisting of nine species were collected at 16 points within a 60 km radius of the Fukushima Dai-ichi Nuclear Power Plant. The activity concentration of (134)Cs ranged from 4.6 to 1000 kBq kg(-1) and for (137)Cs ranged from 7.6 to 1740 kBq kg(-1). A significant positive correlation was found between the (137)Cs activity concentration in lichens and the (137)Cs deposition density on soil (n = 44), based on the calculated Spearman's rank correlation coefficients as r = 0.90 (P < 0.01). The two dominant species, Flavoparmelia caperata (n = 12) and Parmotrema clavuliferum (n = 11), showed strong positive correlations, for which the r values were calculated as 0.92 (P < 0.01) and 0.90 (P < 0.01) respectively. Therefore, Flavoparmelia caperata and Parmotrema clavuliferum are suggested as biomonitoring species for levels of radiocaesium fallout within the Fukushima Prefecture.

Thirty-five-year-old woman with signet ring cell gastric carcinoma secondary to the chernobyl nuclear accident: a case report

The 1986 Chernobyl nuclear accident resulted in radiation exposures throughout much of Europe, with the highest exposures within the city of Pripyat, Ukraine, where the accident occurred. We report a woman who was exposed to the Chernobyl accident at age 13. Beginning in her early thirties, she experienced several years of upper abdominal pain that became progressively more severe. At age 35, she underwent upper endoscopy and gastric biopsy. Histological examination revealed a signet ring cell (SRC) gastric carcinoma. The tumor was discovered at an advanced stage and proved unresectable. She died 3 months following her diagnosis. The mean age for SRC gastric carcinoma diagnosis is about 62 years; the median survival following diagnosis is 13 months. The early appearance and aggressive clinical course of this malignancy in relation to the Chernobyl nuclear accident is discussed.