J. Seo et al.: Radioprotection 2025, 60( 4), 360 – 369 361 Fig. 1. The sampling region, Jeju Island, seas surrounding Korean Peninsula and locations of major nuclear power plant facilities around East Asia countries including South Korea. The current map is modified from Park et al.( 2013).
along the main ocean current of the North Pacific( Aoyama et al., 2020; Tsumune et al., 2012). Aoyama et al.( 2016) suggested that radiocesium from the Fukushima accident could have been transported to waters around the Korean seas through subtropical mode water. A more recent study reported that a few weeks after the FDNPP accident, the activities of artificial radionuclides( 134 Cs, 137 Cs, and 239þ240 Pu) in the surface seawater of the Korean Strait appeared relatively higher( 1 – 2 times for Cs isotopes and 2 – 3 times for 239þ240 Pu) than those observed in previous years( Lee et al., 2022). Given these circumstances, the monitoring of radionuclides in various environments, including seawater and marine products, is crucial for assessing their environmental impacts in South Korea.
A general report states that most radioactive contamination problems caused by tsunami damage to fishery-related facilities and marine products in Japan seemed to have settled during the decade following the FDNPP accident. However, 137 Cs concentrations over the Japanese regulatory limit of
100 Bq kg �1( wet weight) are occasionally observed in fish collected at the FDNPP port( Wada et al., 2022). In a recent study in Korea, Kim et al.( 2019) reported that the distribution of artificial nuclides( 137 Cs, 239þ240 Pu, and 90 Sr) in various marine products collected from the Korean Peninsula in 2015 – 2017 showed no noticeable artificial radioactivity in these marine products. At that time, the authors suggested that 137 Cs levels in fish could considerably increase with size due to bioaccumulation. Bioaccumulation of 137 Cs in fish is a crucial process, as it can have a direct impact on environmental health and food webs; however, data is still insufficient to fully assess these effects.
Therefore, in this study, the 137 Cs activity in seven fish species( armored weaselfish, croaker, flounder, hairtail, catfish, conger, and mackerel) was investigated by size and body part( for the first time in Korea) in the seas surrounding Korea to evaluate the accumulation characteristics of 137 Cs and the annual effective dose( AED) rate varying with body length by seafood consumption.
2 Materials and methods
2.1 Sample preparation
Seven fish species from the northern side of Jeju Island( average water depth of 80 – 130 m; Fig. 1) were collected in October 2021, November 2021, and September 2022 with cooperation from the Korea Fisheries Resources Agency( FIRA). Detailed information on the samples, including fish species( scientific names), habitat, diet, mean lifespan, calculated age, number of individuals, body length, and weight, isprovidedinTable 1. Amongthefishcaughtaround the sampling area, we chose the target species considering two conditions: first, we selected the fish commonly consumed in the Korean diet. Second, we used migratory fish species, not settled fish, to evaluate the bioaccumulation of 137 Cs in fish under various environments. Therefore, these seven species were selected as target species for this study. A total of 238 fish samples were collected with body lengths ranging from 20 to 80 cm. The samples were classified by size( small, medium, and large) according to their body length within each species( when body lengths were similar, we also considered differences in weight). All fish samples were first classified into three groups based on their apparent size and then designated as small, medium, and large groups based on the common classification in the seafood market. The age of the fish, calculated from the correlation between body length and age, was also considered along with body length when classifying the fish samples into the three groups. Subsequently, the samples were immediately dissected into several parts, including the skin, liver, eggs, gonads, muscles, gills, and organs, in the laboratory at the Jeju headquarters of the FIRA. Each of the parts from fish of the same size and species was combined into one to three final samples to ensure sufficient weight for 137 Cs measurement( approximately 400 – 500 g dry weight of muscle tissue). The samples were stored in a freezer at �20 ° C until 137 Cs content measurement.