Radionuclides in marine mammals off the Portuguese coast

Abstract

Radionuclide analyses were performed in tissue samples including muscle, gonad, liver, mammary gland, and bone of marine mammals stranded on the Portuguese west coast during January–July 2006. Tissues were collected from seven dolphins ( Delphinus delphis and Stenella coeruleoalba) and one pilot whale ( Globicephala sp.). Samples were analyzed for 210Po and 210Pb by alpha spectrometry and for 137Cs and 40K by gamma spectrometry. Po-210 concentrations in common dolphin’s muscle ( D. delphis) averaged 56 ± 32 Bq kg −1 wet weight (w.w.), while 210Pb averaged 0.17 ± 0.07 Bq kg −1 w.w., 137Cs averaged 0.29 ± 0.28 Bq kg −1 w.w., and 40K 129 ± 48 Bq kg −1 w.w. Absorbed radiation doses due to these radionuclides for the internal organs of common dolphins were computed and attained a 1.50 μGy h −1 on a whole body basis. 210Po was the main contributor to the weighted absorbed dose, accounting for 97% of the dose from internally accumulated radionuclides. These computed radiation doses in dolphins are compared to radiation doses from 210Po and other radionuclides reported for human tissues. Due to the high 210Po activity concentration in dolphins, the internal radiation dose in these marine mammals is about three orders of magnitude higher than in man.