The prevailing view is that further substantial progress can be made by parameterizing and validating (dynamic) models under controlled, experimental conditions and by comparative studies of areas with well described contamination. The key priorities for RA2 includes:

• Characterize the transfer of radionuclides under field conditions, identifying factors (physico-chemical, biological etc.) that influence the dynamics of transfer (e.g., observatory sites, field tracer studies). Thus, future studies within contaminated sites (observatory sites) such as Chernobyl and Fukushima, and NORM sites will be important to characterize transfer to both aquatic and terrestrial organism groups. Alongside field studies, controlled field experiments will be performed; 1) Controlled aquatic field experiment in contaminated lakes to study uptake and depuration rates of radionuclides in aquatic organisms, and 2) Controlled tracer field experiments to simulate deposition of I-131 and other RN/elements on agricultural land and study tracer redistribution between biological compartments.
• Investigate climate change impacts on transfer of radionuclides (characterize transfer at different temperatures) in different ecosystems and characterize transformation processes affecting radionuclides and stable analogues in aquatic mixing zones or estuaries where changes in speciation occurs, having major influence on biological uptake and effects.
• Quantify 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). Thus, toxicokinetic studies in aquatic and terrestrial organisms will be prioritized to identify the impact of environmental parameters and competing ions along with studies of internal distribution in environmental organisms.
• Further development of models which describe the dynamics of transfer within different ecosystems and accounting for the findings (e.g., ERICA dynamic tool).
• Perform comparative investigations related to speciation, mobility and biological uptake as observed in Chernobyl and Fukushima

There are close connections between these priorities, and the model set up will be used in the experimental design: identifying what are the important parameters required by the model and how might these be derived through experimentation. The models can be used to make predictions and these can be tested through lab experiments and field observation. These considerations still hold true for the next 5 years.