Analysis of measured and modelled technetium-99 time series data in the Nordic marine environment and implications for monitoring design improvement

Radioactivity in the Arctic environment is a central topic within environmental pollution issues. Within the last decade, increased activities were initiated in order to monitor the occurrence of radionuclides from discharges into the North Atlantic and Arctic. Of particular interest is the radionuclide Technetium-99. This highly soluble, beta radiation emitting, man-made radionuclide has been released into the marine environment, from European nuclear reprocessing plants, and has been transported towards the Arctic with the Norwegian Coastal Current. Since both sampling and measurement procedures are expensive and time consuming, radioecological monitoring has strict limitations imposed and therefore needs to be optimized. Within the research project 'RADNOR' funded by the Research Council of Norway), time series from measurements and modelling of Technetium-99 levels for different locations at the southern and northern coast of Norway and in the Arctic (Svalbard) are analysed (spectral and statistical analysis). Most sampling was undertaken monthly from coastal locations. The modelling data originate from the hydrodynamic coupled ice-ocean model 'NAOSIM'. By comparing discharge information, measured and modelled time series, monitoring approaches will be discussed including the number and positioning of monitoring sites, sampling frequency and sampling time. Issues related to the physical processes of ocean current transport, character of the source signal and climatic conditions will be considered within the context of optimizing monitoring design. (author)