Distinction of Migration of Strontium-90 and Cesium-137 for Fukushima Soil and Sediment following the Fukushima Accident

Abstract

Strontium-90 (⁹⁰Sr) and cesium-137 (¹³⁷Cs) were released from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March 2011. Strontium-90 concentration in environment was extremely lower than that of ¹³⁷Cs in the soil after the FDNPP accident. However, ⁹⁰Sr may induce higher risk of health effect to human than ¹³⁷Cs by considering longer biological half-life of ⁹⁰Sr than ¹³⁷Cs. Moreover, there is not sufficient data on ⁹⁰Sr horizontal and vertical distribution compared to ¹³⁷Cs, which is important for predicting their long-term migration. In the present study, the distribution of ⁹⁰Sr and ¹³⁷Cs in the soils of Kawauchi and Fukushima paddy rice fields was investigated and the migration of ⁹⁰Sr and ¹³⁷Cs in Lake Ogi sediment and its forestry catchment area was studied. A rough relation between ⁹⁰Sr and ¹³⁷Cs levels in soil is shown and such insufficient correlation might be defined by the low ⁹⁰Sr concentration and because of global fallout. Furthermore, ⁹⁰Sr gave higher coefficient of variation in comparison to ¹³⁷Cs, portraying that the movement of ⁹⁰Sr is more affected by the environmental factors rather than ¹³⁷Cs. The depth dependency of ⁹⁰Sr and ¹³⁷Cs in Lake Ogi forestry catchment area is shown for both radionuclides, and the activity concentration decreases with the increase of depth. However, the ⁹⁰Sr infiltrates more to 10 cm soil profile in contrast to ¹³⁷Cs, showing ⁹⁰Sr faster vertical migration than ¹³⁷Cs. Sediment to soil ratio for ⁹⁰Sr reported a higher value than that of ¹³⁷Cs, which possibly depicts more horizontal flowing of ⁹⁰Sr from forest soil to lake sediment than ¹³⁷Cs. Consequently, the higher mobility of ⁹⁰Sr than ¹³⁷Cs was proposed.