Radionuclides in marine fishes and birds from Amchitka and Kiska Islands in the Aleutians: Establishing a baseline

Amchitka Island (51 degrees N lat, 179 degrees E long) was the site of three underground nuclear tests from 1965-1971. There have been no substantive studies of radionuclides in marine fishes and birds in the area since the mid-1970's. In this study, levels of Co-60, Eu-52, Sr-90, Tc-99, I-129, Cs-137, and the actinides (Am-241, Pu-238, Pu-239,Pu-240, U-234, U-236, U-236, and U-238) were studied in ten marine fish species (including Pacific Cod Gadus macrocephalus and Pacific Halibut Hippoglossus stenolepis) and five marine bird species (including Glaucous-winged Gulls Larus glaucescens, Tufted Puffins Fratercula cirrhata, and Common Eider Ducks Somateria mollissima) from Amchitka. The same species were collected at a reference site, Kiska Island (52 degrees N lat; 177 degrees E long), about 130 km west of Amchitka. Each sample was a composite of edible muscle from five or more individual fish or birds of similar size (+/- 15%) from the same sampling station. The null hypotheses of no differences among species or between Amchitka and Kiska were tested. Most analytic results were below the minimum detectable activity (MDA), even when 1,000 g sizes and 72 h counting times were used. The only radionuclides detected above the MDA were Cs-137, Am-241, Pu-239,Pu-240, U-234, U-235, and U-238. There were significant differences in Cs-137 as a function of species, but not location, for top predatory fishes. Of the fishes, eight of ten species had Cs-137 values above the MDA for some samples; only one bird, Glaucous-winged Gull, had Cs-137 values above the MDA. The highest concentrations of Cs-137 were in Dolly Varden [Salvelinus manna. 0.780 (Bq kg(-1) wet weight)] and Pacific Cod (0.602 Bq kg(-1)). In aggregate for any actinides, 73 of 234 (31%) composites for fish were above the MDA, compared to only 3 of 98 (3 %) for birds. U-234 and U-238, radionuclides that are primarily natural in origin, were routinely detected in these biological samples, but there were no significant differences in mean concentrations between Amchitka and Kiska. The concentrations of all radionuclides examined at Amchitka are similar to those of other uncontaminated Northern Hemisphere sites, and are lower than those reported for fishes and birds from the Irish Sea in the vicinity of the Sellafield nuclear reprocessing facility, an area with known contamination.