Radioprotection 60-4 | Page 76

J. Seo et al.: Radioprotection 2025, 60( 4), 360 – 369 363

***** n. d. indicates that 137 Cs activity was not detected. † The 137 Cs concentration in Flounder represent measured values and their corresponding uncertainties.

2.2 Measurement of 137 Cs

To measure the 137 Cs activity, the samples were weighed( wet weight) and freeze-dried. Weight was measured to calculate the dry proportion of the samples. Subsequently, the samples were ground and homogenized to minimize geometrical differences between them. The samples were measured using a high-purity germanium detector( Canberra Industries Inc., USA) by counting 137 Cs at 662 keV for at least 2 d to ensure that the counting uncertainties were less than 10 %. The relative efficiency of the 6 ° Co detector was 50 %. Before the sample analyses, the g-spectrometer was calibrated using a mixed g standard solution Multinuclide Standard( Isotope Products Laboratories, USA) in a sample container that was geometrically the same as those containing the samples( 40 mL and 1 L volume of Marinelli beaker for organs and muscles, respectively). The instrument blank was less than 5 % of the average sample activity and the minimum detection limit was 20 mBq kg �1. To validate our analytical procedure, the radionuclide-certified reference material( CRM) IAEA-414( mixed fish from the Irish and North Seas; Pham et al., 2006) from the International Atomic Energy Agency( IAEA) was analyzed together with the samples. The analytical results of the CRM were in good agreement( 5.18 ± 0.38 Bq kg �1, n = 3) with the certified values( 5.18 ± 0.10 Bq kg �1) for 137 Cs.

2.3 Calculation of concentration factor and annual effective dose rates of 137 Cs

The concentration factor( CF), which is the ratio of the contaminant concentration in biota to the same substance in the surrounding ambient water, has been widely used to assess the uptake and accumulation of 137 Cs in biota( Carvalho, 2018), as well as in environmental radioactivity and radioecology reports( Ancellin and Guegueniat, 1979; Rand, 1995; Whicker et al., 1997). CF was calculated as follows:

CF ¼ Concentration per unit mass of fish � mBq kg�1 wet weight �

Concentration per unit mass of sea water mBq kg �1;

where the 137 Cs activity in fish was based on measurements from the muscle( the main edible part), while the 137 Cs activity in seawater( 1.62 ± 0.23 mBq kg �1) was measured in seawater samples( n = 4, range: 1.37 – 1.91 mBq kg �1) collected at the same locations and during the same periods of the fish sampling( KINS, 2023).

The AED rates( mSv y �1) were calculated to evaluate the potential health risks of radiation exposure in environmental and human health assessments. In this study, the AED of 137 Cs was examined in muscle tissue to assess the radiological hazards derived from fish consumption. The AED was calculated as follows( Radiation, 2000):

� AED mSvy �1

¼ AAR eT ð Þ I y;

where A AR represents the mean activity of radionuclides in marine products( mBq kg �1), e( T) is the effective dose coefficient( 1.30 10 �5 Sv mBq �1; Eckerman et al., 2012), and I yr is the annual intake per person in South Korea( kg y �1). For this study, the following intake data were sourced from the 2022 Food Balance Sheets by the Korea Rural Economic Institute( KREI, 2022): croaker( 0.22 kg y �1), flounder( 0.69 kg y �1), hairtail( 0.90 kg y �1), catfish( 0.05 kg y �1),