| Summary: | Northern Fennoscandia has experienced an unparalleled mineral exploration boom since around 2005. At the same time, there has been increasing awareness of the potential environmental impact of non-nuclear industries that extract and/or process ores containing naturally occurring radionuclides. Industrial activities may result in significant environmental problems if the waste generated during ore processing is not adequately managed. In 2010, a new project was launched with an objective to study the mobility of uranium series radionuclides from diverse mill tailings in a northern boreal environment in Finland. Three sites were investigated: the Talvivaara Ni-Cu-Zn-Co mine in central Finland, a former phosphate mine at Sokli, Finnish Lapland, and a former pilot-scale uranium mine at Paukkajanvaara, eastern Finland. The mobility of radionuclides from the mill tailings at Sokli was examined in order to assess the potential environmental impact of past and future mining activities. Mineralogical studies did not indicate that uranium or thorium have been mobilized from altered pyrochlore-group minerals in the Sokli ore or tailings. In the tailings pond, no clear trends were observed in the activity concentrations of uranium, radium or thorium isotopes in the surface layers of the mill tailings. In subsurface samples, an increase in the concentration of these isotopes can be seen when approaching the pond at the distal end of the sludge field. However, this increase is most likely to a consequence of compositional changes in material discharges. The results of the sequential extraction tests suggested that neither uranium nor thorium is in an exchangeable form and could potentially be released to the environment. Uranium (4% of the total concentration) was partly soluble under weakly acidic conditions, whereas thorium was tightly bound in mineral phases. At the former Paukkajanvaara uranium mine in Eno, the aim of the study was to examine the potential for further mobilization of radionuclides after remediation of the ...
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