Radionuclides in fishes and mussels from the Farallon Islands Nuclear Waste Dump Site, California

The fate of the main naturally occurring radionuclides in mussels (Mytilus edulis) and their radiological impact on human beings

A comprehensive study was made on the activity concentrations, concentration factors, and radiation exposure impact of the main naturally occurring radionuclides in blue mussels collected in the Mediterranean Sea. The results showed that the concentrations of the measured radionuclides were site-specific and all detectable in gram-size samples of the soft tissues of the mussels, especially, some activity concentrations can reach as high as 16.8-102 Bq kg^-1 for ²¹⁰Po, 16.7-66.8 Bq kg^-1 for ⁴⁰K and 0.602-3.21 Bq kg^-1 for ²¹⁰Pb. The obtained mean concentration factors in the soft tissues of the mussel samples are 6.30 ± 2.40 for ²³⁸U and ²³⁴U, 4.68 ± 1.73 for ²³⁵U, (2.72 ± 1.73) × 10⁴ for ²³²Th and ²³⁰Th, 480 ± 265 for ²²⁸Th, 33.3 ± 13.3 for ²²⁶Ra, 100 ± 52 for ²²⁴Ra and 29.0 ± 14.7 for ²²⁸Ra, (1.22 ± 0.72) × 10⁴ for ²¹⁰Po, 517 ± 280 for ²¹⁰Pb and 2.57 ± 0.80 for ⁴⁰K. The estimated mean committed effective doses of ²³⁸U, ²³⁴U, ²³⁵U, ²³²Th, ²³⁰Th, ²²⁸Th, ²²⁶Ra, ²²⁴Ra, ²²⁸Ra, ²¹⁰Po, ²¹⁰Pb and ⁴⁰K to an adult due to mussel ingestion are 0.073 ± 0.027, 0.089 ± 0.035, 0.0030 ± 0.0011, 0.128 ± 0.098, 0.117 ± 0.081, 0.056 ± 0.031, 0.145 ± 0.058, 0.0487 ± 0.0250, 0.395 ± 0.200, 352 ± 209, 6.00 ± 3.25 and 1.74 ± 0.54 μSv a^-1, respectively. Among the elements or nuclides, ²¹⁰Po is the dominant dose contributor which contributes 96.9% of total dose fraction, and the relative dose contribution is in the order of ²¹⁰Po > ²¹⁰Pb > ⁴⁰K > radium ≥ thorium ≥ uranium.

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

Amchitka Island (51degrees 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 60Co, 52Eu, 90Sr, 99Tc, 129I, 137Cs, and the actinides (241Am, 238Pu, 239,240Pu, 234U, 235U, 236U, and 238U) 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 137Cs, 241Am, 239,240Pu, 234U, 235U, and 238U. There were significant differences in 137Cs as a function of species, but not location, for top predatory fishes. Of the fishes, eight of ten species had 137Cs values above the MDA for some samples; only one bird, Glaucous-winged Gull, had 137Cs values above the MDA. The highest concentrations of 137Cs were in Dolly Varden [Salvelinus malma, 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. 234U and 238U, 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.