¹³⁴Cs and ¹³⁷Cs radioactivity in soil and moss samples of Jeju Island after Fukushima nuclear reactor accident.

Specific activities of (134)Cs and (137)Cs in surface soil and moss samples were investigated at 12 locations of Jeju Island, Korea. Specific activities of (134)Cs and (137)Cs in the surface soil vary from less than MDA to 17 Bq/kg and from 12 Bq/kg to 109 Bq/kg, respectively. Specific activities of (134)Cs and (137)Cs in moss samples lie in the range 6 Bq/kg-39 Bq/kg and 15 Bq/kg-41 Bq/kg, respectively. The activity ratios (134)Cs/(137)Cs in the soil samples are much less than the reference value of about 1.0, but they are close to 1.0 in the moss samples. Average amount of (137)Cs added to the surface soil after the Fukushima accident is estimated to be 7.8 ± 1.7 Bq/kg. The depth profile of (137)Cs specific activity has a lognormal shape with a peak between 5 cm and 7.5 cm below the ground. For the cored soil sample, (134)Cs was detected up to 3 cm below the ground.