Bomb Cs-137 In Modern Honey Reveals A Regional Soil Control On Pollutant Cycling By Plants

Cs-137 is a long-lived (30-year radioactive half-life) fission product dispersed globally by mid-20th century atmospheric nuclear weapons testing. Here we show that vegetation thousands of kilometers from testing sites continues to cycle Cs-137 because it mimics potassium, and consequently, bees magnify this radionuclide in honey. There were no atmospheric weapons tests in the eastern United States, but most honey here has detectable Cs-137 at >0.03Bqkg(-1), and in the southeastern U.S., activities can be >500 times higher. By measuring honey, we show regional patterns in the biogeochemical cycling of Cs-137 and conclude that plants and animals receive disproportionally high exposure to ionizing radiation from Cs-137 in low potassium soils. In several cases, the presence of Cs-137 more than doubled the ionizing radiation from gamma and x-rays in the honey, indicating that despite its radioactive half-life, the environmental legacy of regional Cs-137 pollution can persist for more than six decades. Radioactive Cs-137 is a fission product remaining in the environment from mid-20th century nuclear testing. Here the authors show that vegetation thousands of kilometers from testing sites continues to cycle Cs-137, and consequently, bees magnify this contaminant in honey in regions with low soil potassium.