||Consideration on the Long Ecological Half-life Component of 137Cs in Demersal Fish Based on Field Observation Results Obtained after the Fukushima Accident
Tagami, KeikoUchida, Shigeo
Environmental Science and Technology
1811 , 2016-02 , ACS
Radiocesium concentrations in most marine fish collected off the coast of Fukushima and surrounding prefectures have decreased with time, and four years after the Fukushima Daiichi Nuclear Power Plant accident occurred, radiocesium concentrations have generally fallen below the detectable level (ca. <10 Bq kg-1-raw). Only in some demersal fish species have detectable concentration levels been found and even these species have showed slow radiocesium decreases. The food web was considered as the major factor causing this phenomenon, however, slow elimination rates of radiocesium from these fish species also could be the cause. We examined the latter effect by considering that the 137Cs concentration decrease trend in fish could be fit with a set of three exponentially decreasing components, that is, having fast, intermediate and slow ecological half-lives. The slow half-life component was calculated using a 400-1500 d period of monitoring results for Japanese rockfish (Sebastes cheni) in order to compare previous reported laboratory results for biological half-life. The obtained ecological half-lives ranged from 274 – 365 d, and these values agreed with the biological half-life of this fish species. This result implied that the slow biological half-lives of radiocesium in some demersal fish species made their radiocesium contamination periods longer.