An analysis of the environmental mobility of radiostrontium from weapons testing and Chernobyl in Finnish river catchments

The mobility of radiostrontium within the Arctic environment and surrounding area has been studied by analysing the mobility of ⁹⁰Sr in river catchments that are within Finland. The environmental mobility of ⁹⁰Sr deposited by both nuclear weapons testing and the Chernobyl accident has been investigated in five Finnish river catchments. Different models assessing the time-dependent mobility of ⁹⁰Sr have been evaluated. No significant differences were found between the mobility of ⁹⁰Sr from nuclear weapons tests and from the Chernobyl accident. Model parameters obtained by fitting to the measurements of the deposition and runoff rates of the nuclear weapons test fallout gave predictions which were consistent with the mid- and long-term contamination by the Chernobyl fallout. A comparison of ⁹⁰Sr with ¹³⁷Cs showed that they had similar mobility on deposition but, as time passed, the relative mobility of ⁹⁰Sr increased with respect to ¹³⁷Cs over a period of 5-8 years. Once the relative migration of ⁹⁰Sr with respect to ¹³⁷Cs reached equilibrium, its runoff rate was, on average, approximately an order of magnitude greater than ¹³⁷Cs.