In early September of 2011, Ministry of Education, Culture, Sports, Science and Technology measured marine soil offshore of Ibaraki, Fukushima and Miyagi.
They published the result on 1/20/2012 finally but it shows marine soil contains alpha and beta nuclides.
9/8/2011
Pu-238 : 0.015 Bq/Kg
Pu-239+240 : 0.97 Bq/Kg
Am-241 : 0.50 Bq/Kg
Sr-90 (Bq/Kg)
9/14 : 0.38
9/14 : 0.12
9/13 : 0.32
9/10 : 0.20
9/9 : 0.20
9/8 : 1.9
Iori Mochizuki