Radionuclide biological half-life values for terrestrial and aquatic wildlife

The equilibrium concentration ratio is typically the parameter used to estimate organism activity concentrations within wildlife dose assessment tools. Whilst this is assumed to be fit for purpose, there are scenarios such as accidental or irregular, fluctuating, releases from licensed facilities when this might not be the case. In such circumstances, the concentration ratio approach may under- or over-estimate radiation exposure depending upon the time since the release. To carrying out assessments for such releases, a dynamic approach is needed. The simplest and most practical option is representing the uptake and turnover processes by first-order kinetics, for which organism- and element-specific biological half-life data are required. In this paper we describe the development of a freely available international database of radionuclide biological half-life values. The database includes 1907 entries for terrestrial, freshwater, riparian and marine organisms. Biological half-life values are reported for 52 elements across a range of wildlife groups (marine = 9, freshwater = 10, terrestrial = 7 and riparian = 3 groups). Potential applications and limitations of the database are discussed

Radiocaesium transfer and radiation exposure of frogs in Fukushima Prefecture

The International Commission on Radiological Protection has proposed an environmental assessment framework. This includes ionising radiation exposure assessment for different frog life-stages, but radiocaesium transfer parameters are unavailable. We collate data from the Fukushima Prefecture (contaminated by the Fukushima accident) and estimate radiocaesium concentration ratio (CR ) values for tadpoles and adult frogs, presenting the largest available amphibian CR dataset. In total, 513 adult frogs and 2540 tadpoles were analysed in 62 and 59 composite samples respectively. Results suggest that equilibrium was reached between water and amphibian radiocaesium activity concentrations circa one-year after the accident. Radiocaesium transfer to tadpoles was higher than to adult frogs. Dose rates were estimated for different life-stages and species in both the aquatic and terrestrial environment. Estimated dose rates to adults and tadpoles were typically similar because external exposure dominated for both organisms; frogspawn dose rates were estimated to be orders of magnitude lower than other life-stages. For the two sites assessed, which were outside of the most contaminated areas of the Fukushima Prefecture, estimated dose rates were below those anticipated to present a risk to wildlife populations; it is likely that dose rates in more contaminated areas were in excess of some effects benchmark values

A peach germplasm collection for increasing the genetic diversity in European breeding programs

Trabajo presentado al VIII International Peach Symposium, celebrado en Matera (Italia) del 17 al 20 de junio de 2013.European breeding programs are hampered by the low intraspecific genetic diversity, which is due to the self-compatibility of this homozygous species along with the low number of genotypes introduced and thus used for breeding. In 2009, four research institutions which carried out peach breeding programs in Aragon, Catalonia, Valencia and Murcia, started a new peach germplasm collection worldwide aimed at enlarging the peach genetic diversity available for breeding. The plant material was introduced from germplasm collections located in China, Central Asia, Iran and the USA (National Germplasm Repository of Davis). Sanitary status was assessed by molecular diagnosis of known diseases caused by virus, viroid, bacteria and phytoplasm pathogens. Healthy plant material was grafted and maintained in quarantine conditions. The new germplasm collection was established in two places: Zaragoza as high chilling and Murcia as low chilling requirements. Pomological and molecular data were gathered and a public database constructed. The descriptors used were from the National Center for Genetic Resources from the INIA. Introduced budwood and seeds resulted in more than 250 new genotypes from 15 countries. The molecular analysis of a subset of the collection with 21 SSR markers evenly distributed in the genome resulted in a high number of alleles per SSR (mean A=9.5) and low observed heterozygosity (mean Ho=0.38). Variability was further assessed by geographic origin. Population structure analysis revealed the existence of 8 subpopulations explained, in some cases, by the geographic origin of the genotypes. As a result of the project a new database containing 95 accessions and 38 variables is available.Peer reviewe

Do fungi need to be included within environmental radiation protection assessment models?

Fungi are used as biomonitors of forest ecosystems, having comparatively high uptakes of anthropogenic and naturally occurring radionuclides. However, whilst they are known to accumulate radionuclides they are not typically considered in radiological assessment tools for environmental (non-human biota) assessment. In this paper the total dose rate to fungi is estimated using the ERICA Tool, assuming different fruiting body geometries, a single ellipsoid and more complex geometries considering the different components of the fruit body and their differing radionuclide contents based upon measurement data. Anthropogenic and naturally occurring radionuclide concentrations from the Mediterranean ecosystem (Spain) were used in this assessment. The total estimated weighted dose rate was in the range 0.31–3.4 μGy/h (5th–95th percentile), similar to natural exposure rates reported for other wild groups. The total estimated dose was dominated by internal exposure, especially from 226Ra and 210Po. Differences in dose rate between complex geometries and a simple ellipsoid model were negligible. Therefore, the simple ellipsoid model is recommended to assess dose rates to fungal fruiting bodies. Fungal mycelium was also modelled assuming a long filament. Using these geometries, assessments for fungal fruiting bodies and mycelium under different scenarios (post-accident, planned release and existing exposure) were conducted, each being based on available monitoring data. The estimated total dose rate in each case was below the ERICA screening benchmark dose, except for the example post-accident existing exposure scenario (the Chernobyl Exclusion Zone) for which a dose rate in excess of 35 μGy/h was estimated for the fruiting body. Estimated mycelium dose rate in this post-accident existing exposure scenario was close to the 400 μGy/h benchmark for plants, although fungi are generally considered to be less radiosensitive than plants. Further research on appropriate mycelium geometries and their radionuclide content is required. Based on the assessments presented in this paper, there is no need to recommend that fungi should be added to the existing assessment tools and frameworks; if required some tools allow a geometry representing fungi to be created and used within a dose assessment

A boom‐or‐bust approach — the ‘Glass Cannon’ hypothesis in host microbiomes

In Focus: Dunphy, CM, Vollmer, SV, Gouhier, TC. (2021) Host–microbial systems as glass cannons: Explaining microbiome stability in corals exposed to extrinsic perturbations. Journal of Animal Ecology, 90, 1044–1057. The importance of symbiotic microbial communities for the functioning of animal hosts is now well‐documented; however, the interactions between host microbiomes and stress are less well‐understood. Dunphy et al. used a common garden experiment to show that host–microbiomes vary in their resilience across different coral species. The authors then used mathematical modelling to provide novel evidence that species with microbiomes that are regulated by host processes are robust to perturbation from stressors, but that robustness comes at a higher cost to the host. Conversely, species with microbiomes that are regulated by microbial processes are generally much more resilient and cheaper to support, but when disrupted by external stressors, the communities break down entirely—these latter species are termed ‘glass cannons’. This novel hypothesis has important implications for how host microbiomes function in a rapidly changing world that exposes animal hosts to multiple biotic and abiotic perturbations

Radon-222 dose rates to burrowing mammals

Estimates of absorbed dose rates as a consequence of exposure of wildlife to natural background radionuclides are required to put results of assessments conducted for releases of radionuclides from licensed sites into context. There have been recent review papers in which estimated dose rates to marine, freshwater and terrestrial wildlife (specifically the ICRP Reference Animals and Plants (ICRP 2008)) from 40K and radionuclides in the 238U and 232Th series have been presented (Beresford et al. 2008; Hosseini et al. 2010). Average estimated weighted absorbed dose rates to all organisms considered were in the region of 1 µGy h-1. However, there is to date, only one study published in the refereed literature which estimates dose rates to burrowing mammals as a consequence of inhalation of 222Rn (Macdonald & Laverock 1998). The results of this study suggested that dose rates from 222Rn may be an order of magnitude greater than those received from 40K, and 238U and 232Th series radionuclides. However, the study was conducted in an area of Canada with radon-rich soils and the results may not be typical for most areas