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

Abstract

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