RA2 aims to improve our understanding of how radionuclides are transferred within aquatic and terrestrial ecosystems. Both naturally radionuclides as well as transuranic and fission products are in focus. To improve impact assessment models transfer constants based on equilibrium concepts hitherto used are replaced with more environmental realistic dynamic, process-based models.  Such improved characterization of transfer processes (and their variability) reduces uncertainties in predicting radionuclide behaviour.

To characterise dynamic ecosystem transfer of radionuclides our research specifically focuses on:

• The mobility of radionuclides, taking speciation into account,
• The influence of environmental factors on the uptake by and accumulation in organisms
• The influence of biological factors on the uptake by and accumulation in organisms including the use of extrapolation approaches like ‘phylogenetic’ analysis,

RA2 links with all other RAs : transfer is on inputs from Source Term and Release Scenarios (RA1),  studying transfer occurs in tandem with Biological response (RA3) to quantify external and internal exposures, and transfer forms an integral part of Risk Assessment (RA4).

A large part of data are collected during field work in Norway and in many other locations globally, both at  high natural background and contaminated sites.  Furthermore, controlled experiments are conducted under laboratory and field conditions and findings are compared with those from well described, contaminated areas to derive parameters and validate (dynamic) models.  

Achievements so far:

Fieldwork  Several fieldwork campaigns have been arranged to characterise radionuclides/stable analogues and key influencing factors:

• NORM sites: focused on both Uranium-rich sites (i.e. sites with alum shale) and the Thorium-rich Fen site in Norway.
• Various sites in Norway – Tjøtta, Jotunheimen, Vikedal, TOV (NINA’s terrestrial monitoring sites)
• Sites contaminated after nuclear accidents: Chernobyl (Ukraine), Fukushima (Japan) and Palomares (Spain), and sites in Norway with fallout from accidents, all characterised by different source terms and ecosystem transfer.
• Objects; sunken nuclear submarines in the Kara, Barents and Norwegian Sea, and dumped radioactive material in the Kara Sea.

In addition, samples are received from partners world-wide.

Model experiments Several model experiments in the laboratory and controlled experiments in the field have been performed to obtain information on:

• Key factors influencing speciation (UV; pH, complexing ligands etc.)
• Bioavailability and uptake of radionuclides in different organisms at different life stages
• Tissue distributions of radionuclides
• Uptake rates of radionuclides directly from the water and via diet from primary producers to primary and secondary consumers
• the effects of radionuclide speciation on dynamic uptake and biological half-life under controlled laboratory conditions (e.g., Kd, CR, TF/TC/Tag, BCR, tissue distribution and protein interaction).
• Depuration rates of radionuclides and body retention time
• Field tracer experiments to simulate deposition and redistribution of Iodine and strontium in agricultural systems
• Impact of environmental factors (competing ions, pH, temperature etc) and mixture effects with other stressors e.g., trace metals

Transfer

• Several publications in international peer review journals, reports/ proceeding
• Key factors such as pH, complexing ligands, UV and ionic strength have been identified to influence radionuclide speciation and bioavailability
• Analyses of transportation and uptake of Cs and Sr in the Chernobyl exclusion zone (Bondar et al., 2015), Cs in Scandinavian wolf, Lynx and wolverine (Gjelsvik et al., 2016)
• Field experiments demonstrate that uptake and depuration rates of Cs and Sr in fish are season dependent
• Distribution of I-129 in sediment-freshwater and fish have been determined; Comparison between results from Fukushima and Chernobyl have been made
• The link between bioaccumulation and effects differs between life stages and radionuclides
• Concentrations, speciation and uptake of NORM (U and Po) and metals from alum shale (Road and Tunnel Construction areas) have been determined
• Elemental distributions at a reference site in Norway were characterised (Thørring et al., 2016); Whole body concentration ratios (CRs) for all Reference Animal Plant (RAP)-element combinations were quantified. Selected data were described for each RAP with information about the importance of various organs/tissues on the whole-body concentration (or CR) for vertebrates and crabs

Models 

• A new version of a risk assessment tool (ERICA) to determine the impact of radionuclides on the environment has been developed drawing upon development made in RA2/UMB2 (Brown et al., 2016).
• Dynamic models for predicting the transfer of radionuclides in terrestrial and marine systems have been developed and applied to actual releases from the Fukushima-Daiichi accident (Strand et al., 2014) and to hypothetical accidents involving dumped nuclear objects (e.g. the Russian submarine K-27) in the Arctic.
• An ‘Extrapolation approach’ based upon a phylogenetic analysis has been developed to predict radionuclide transfer to marine organisms although subsequent testing showed low efficacy.
• Ongoing studies on reindeer in the Jotunheimen area of Norway has allowed transfer to be modelled accounting for spatial and temporal factors.
• Studies on Iodine in cow and uranium in fish have generated data allowing the modelling of dynamic tissue distribution
• The types of dynamic models that have been developed and applied in CERAD have generally drawn upon generic parameter values

Key papers:

Strand P., Sundell-Bergman S., Brown J.E., Dowdall M. (2017). On the divergence in assessment of environmental impacts from ionising radiation following the Fukushima accident. Journal of Environmental Radioactivity 169–170, 159-173.

Brown, J.E., Alfonso, B., Avila, R., Beresford, N.A., Copplestone, D., Hosseini A. (2016). A new version of the ERICA tool to facilitate impact assessments of radioactivity on wild plants and animals. Journal of Environmental Radioactivity 153, 141-148.

Thørring, H., Brown, J.E., Aanensen, L., Hosseini, A. (2016). Tjøtta – ICRP reference site in Norway. Strålevern Rapport 2016:9. Østerås: Statens strålevern.

Gjelsvik, R., et al. Organ distribution of 210Po and 137Cs in lynx (Lynx lynx), wolverine (Gulo gulo) and wolves (Canis lupus). II International Conference On Radioecological Concentration Processes (50 years later), November 2016, Seville, Spain.

Bondar, Y.I., Nenashev, R.A., Kalinichenko, S.A., Marchenko, Y.D., Dowdall, M., Standring, W.J.F., Brown, J., Pettersen, M.N., Skipperud, L., Zabrotski, V.N. (2015). The distribution of 137Cs, 90Sr, and 241Am in waterbodies of different origins in the Belarusian part of Chernobyl exclusion zone. Water, Air and Soil Pollution 226(3), 63.

Strand, P., Aono T., Brown, J.E., Garnier-Laplace, J., Hosseini, A., Sazykina, T., Steenhuisen, F., Vives i Batlle, J. (2014). Assessment of Fukushima-derived radiation doses and effects on wildlife in Japan. Environmental Science & Technology Letters 1 (3), 198-203.