Records of Fukushima accident-derived cesium-137 in the Chukchi Sea sediment: Implication for a new time marker?

The Fukushima accident released a large amount of ¹³⁷Cs into the environment. In this study, we used a sediment core collected from the Chukchi Sea during the 2018 Arctic Xuelong Scientific Expedition to investigate the Fukushima accident-derived ¹³⁷Cs. Using ²¹⁰Pb (²¹⁰Pb_ex) and ¹³⁷Cs chronology, we find that the ¹³⁷Cs peak at 2 cm corresponds to the year 2011±1. This implies that the Fukushima accident-derived ¹³⁷Cs arrived in the Chukchi Sea much earlier than that by oceanic current transport. Our three calculation results (sediment core deposition flux: (4.0±0.4)×10⁻⁶ Bq cm⁻² d⁻¹; atmospheric deposition flux: (1.4–2.5)×10⁻⁵ Bq cm⁻² d⁻¹; biological deposition flux: (4.0±0.9)×10⁻⁶ Bq cm⁻² d⁻¹) suggest that atmospheric deposition and biological transport could cause such peak records. The results indicate that the 2011 peak of ¹³⁷Cs can serve as a new temporal marker for estimating the sedimentation rate in the region affected by the Fukushima accident. We state that assessing the impact of coastal accidents and subsequent wastewater discharge in marine environments needs more consideration of biological carryover in addition to physical oceanography transport.