Effects of Nuclear Test Fallout (Japan)

Nuclear tests in the atmosphere were frequently conducted from late 1950s to early 1960s, causing a large amount of radioactive fallout across the globe. Radioactive cesium and radioactive strontium, etc. detected before March 11, 2011, are considered to be part of such fallout (p.78 of Vol. 1, “Effects of Radioactive Fallout due to Atmospheric Nuclear Testing”).

As a result of a soil survey conducted in Hokkaido in 2009, Cs-137 was detected as deep as 40 cm from the ground surface in plowed soil, such as paddy fields and upland fields, but it was found that in forests where soil is not plowed, Cs-137 was mostly located within 20 cm from the ground surface.

How deep radioactive cesium is adsorbed in soil depends on the property of soil, but it is known that Cs-137 tends to remain in the surface layer also in Japan.
(Related to p.179 of Vol. 1, “Distribution of Radioactive Cesium in Soil”)

• Included in this reference material on March 31, 2013
• Updated on March 31, 2015