Analysis of the typical radionuclides for neon flying squid of the high seas fisheries in North Pacific Ocean and risk assessment in 2013

To understand the pollution effect of radionuclides emitted from Fukushima nuclear accident on marine organisms, we collected flying squid samples in the North Pacific Ocean (40°-44°N, 145°-160° E) from August to November in 2013. Radionuclides' concentrations at different localities were analyzed by the ultra-low background high purity germanium (HPGe) γ spectrometer. The result showed that nuclide specific activities of ¹³⁴Cs and^110mAg were not higher than the background values, while those of ²¹⁰Pb, ¹³⁷Cs and ⁴⁰ K were detected in all samples. Specific activity ranges of ²¹⁰Pb, ¹³⁷ Cs and⁴⁰ K for neon flying squid were 0.99-7.60 Bq·kg^-1, the mininum detection limit to 0.37 Bq·kg^-1 and 46.00-107.00 Bq·kg^-1, respectively. The 250-300 mm mantle length group of neon flying squid had the highest nuclide concentration of ²¹⁰Pb, and the minimum concentration of²¹⁰ Pb was found in the 200-250 mm and >400 mm groups. The 200-250 mm mantle length group had the highest nuclide concentration of ¹³⁷ Cs, and the 250-300 mm and 350-400 mm groups had the minimum. The 250-300 mm mantle length group had the highest nuclide concentration of ⁴⁰ K, and the 150-200 mm group had the minimum, and the overall distribution was much more uniform. Nuclide concentration distributions were different in different organs of neon flying squid, but all highest values were detected in innards. Risk assessment showed that the entropy-values of all tested marine life value and basic value of radionuclide content in the fishing grounds of North Pacific high seas were not higher than 1, indicating there was no high risk of the radiation on fishery resources temporarily in North Pacific Ocean. The study provided the theory basis for assessment of the marine ecological environment and public health hazard resulted from Fukushima nuclear accident.