Strontium-90 and Cesium-137 Levels in Soils of Various Types at Niigata Prefecture, Japan

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^<90>Sr and ^<137>Cs contents of soils, mostly from radioactive fallouts of the past nuclear explosions, were estimated at 15 locations in Niigata Prefecture. Fifteen locations include paddy fields, meadow, grass fields, forest and dried lagoon. ^<90>Sr contents of the soils, except forest and dried lagoon, ranged from 81 to 315 mCi/km^2 and ^<137>Cs ranged from 234 to 451 mCi/km2. These results indicate that the soils except forest and lagoon were highly contaminated with ^<90>Sr and ^<137>Cs from radioactive fallouts. The high activities of ^<90>Sr and ^<137>Cs were noted in rice paddy fields. ^<90>Sr of 316 mCi/km^2 of Muramatsu Town and ^<137>Cs of 451 mCi/km^2 of Gosen City are probably the highest values recorded in Japan. These high values may reflect the high annual rainfall of these areas. Relatively low ^<90>Sr and ^<137>Cs levels of forest soils and dried lagoon suggest that ^<90>Sr in strongly acidic, sandy and low humic soils were washed away rather easily by water and that ^<137>Cs in very reductive paddy soil and in volcanic ash soil were also easily removed by water. The distribution of ^<90>Sr and ^<137>Cs in relation to various depth of soils indicates that the monitering of two nuclides in soils should be carried out from the soil sample dug up to 50 cm depth.
日本放射線影響学会の論文