Radioactive status of seawater and its assessment in the northeast South China Sea and the Luzon Strait and its adjacent areas from 2011 to 2014.

To understand the impact of the Fukushima nuclear accident (FNA), 137Cs, 134Cs, 90Sr, and gross beta were analyzed in the northeast South China Sea (NSCS), the Luzon Strait (LS) and its adjacent areas. 137Cs, 90Sr, and gross beta values in the NSCS were similar to those prior to the FNA. 90Sr and 137Cs in the LS and its adjacent areas were consistent with those in the NSCS. The high 137Cs-peak values occurred at depth of 150 m whereas the high 90Sr-peak values occurred at depth of 0.5 m. The 137Cs and gross beta mean values in Cruise I were higher than those in Cruise II whereas the 90Sr mean value was just the reverse. 134Cs in all seawater were below the minimum detectable activity. The past and present data since the 1970s suggested 137Cs and 90Sr in the study areas still originated from global fallout and the FNA influence were negligible.