MEXT conducted emergency sea area monitoring around Fukushima Dai-ichi NPP from March 23, 2011 to investigate the distribution of radioactive substances released by the Fukushima Dai-ichi NPP accident following the great east Japan earthquake. In the beginning, observation was mainly conducted in the offshore of Fukushima Prefecture. Upon the initiation of "Enhancement of Sea Area Monitoring (April 22, 2011, Headquarters against Nuclear Disasters)", wider area monitoring including offshore of Miyagi Prefecture and Ibaraki Prefecture was conducted. Dust over the sea was filtered by dust sampler at each sampling point and then the filter bagged up in the plastic bag was measured with Germanium semiconductor detector. The dust sampling was ended on July 31, 2011 because measured values dropped below detection limit since May 2011. The data here was created based on the measurement results of dust monitoring.
Publicly available data collected from the website of the relevant organizations and converted into CSV, XML, and KML formats that were easy to use.