Plastics as vectors of radiocesium in river environments of Fukushima, Japan

Battulga, B.*; Nakanishi, Takahiro   ; Ikenoue, Tsubasa  ; Atarashi-Andoh, Mariko  ; Koarashi, Jun   

Plastic debris is widely recognized as a major environmental challenge, yet its interactions with radionuclides remain poorly understood. Here, we investigated the behavior and fate of plastics and associated radiocesium (Cs) in the coastal river environments of Fukushima, Japan, to elucidate their interactions and the role of plastics as vectors for Cs transport into the coastal ocean. At four river mouth sites, we characterized the properties of plastics, including microplastics, and elucidated the activity concentration of Cs associated with them. Our findings reveal that Cs was concentrated in biofilms on plastics, but the radioactivity of biofilm-associated plastics was lower than that of the surrounding natural media. Furthermore, we estimated the daily fluxes of plastics (1.3-301.4 kg/day) and associated Cs (5-6,752 Bq/day) in the studied rivers across different seasons. This study provides the first quantitative assessment of plastic-associated Cs flux in the riverine environments.