Activity concentration measurements of selected radionuclides in seals from Canadian Arctic

The activity concentrations of naturally occurring radionuclides (such as ²²⁶Ra, ²¹⁰Pb and ²¹⁰Po) and long lived ¹³⁷Cs were measured in a total of 119 tissue samples (43 blubber, 43 liver, and 33 muscle samples) from 40 ringed seals and 4 bearded seals collected in the Arviat area of Canada during the fall of 2014. Activity concentration of ²¹⁰Po was measured in all seal liver and muscle samples individually. The average ²¹⁰Po activity concentrations were 25 ± 7.6 Bq/kg fresh weight (fw) in muscle and 211 ± 58 Bq/kg fw in liver for ringed seals, and 20 ± 6.1 Bq/kg fw in muscle and 231 ± 150 Bq/kg fw in liver for bearded seals. Due to insufficient sample material for most samples collected, gamma counting for radioactive caesium and radiochemical analysis for ²²⁶Ra and ²¹⁰Pb were performed for pooled samples. Activity concentrations of ²¹⁰Pb and ²²⁶Ra were generally below detection limits. While ¹³⁴Cs activity concentration was not detectable, ¹³⁷Cs activity concentration was detected in muscle and liver samples. On average, the ¹³⁷Cs activity concentrations were 0.25 ± 0.05 and 0.12 ± 0.04 Bq/kg fw in muscle and liver samples of ringed seals, and 0.11 ± 0.02 and 0.10 ± 0.03 Bq/kg fw in muscle and liver samples of bearded seals, respectively. Neither ²¹⁰Po nor ¹³⁷Cs were detected in the blubber samples. This study confirmed that ²¹⁰Po is the dominant contributor to radiation doses resulting from seal consumption. Man-made contaminant ¹³⁷Cs only contributes less than 0.01% of the total ingestion dose obtained from Arviat seals.