Comment on bg-2021-10

Abstract

We observed 3 H activity concentrations and the 137 Cs activity concentrations during the SoSo 5 rivers cruise in 2014 and at the Tomioka port in 2014-2018. The 3 H activity concentrations at coastal stations located close to the Fukushima coast ranged from 90 Bq m -3 to 175 Bq m -3 , and decreased between 67 Bq m -3 to 83 Bq m -3 at the stations located 12-16 km from the coast. The 3 H activity concentration at 20 the estuaries and ports, except at 56 north canal of the FNPP1 site, are around 200-500 Bq m -3 and slightly lower than the 3 H activity concentration of 500-600 Bq m -3 observed in the rivers. These gradients of the 3 H activity concentrations in the coastal region might indicate the large effect of 3 H flux through the rivers.On the other hand, the 3 H activity concentration at 56N of the FNPP1 site was significantly high compared to the 3 H activity concentration in surrounding waters both north and south of the FNPP1 site and in river 25 waters. It should also be noted that the 3 H activity concentrations were similar at the stations located both north and south of the FNPP1 site, while the 137 Cs activity concentrations were lower at the stations north