Sources of environmental radionuclides and recent results in analyses of bioaccumulation. A review

Ecological investigations concentrate on the biosphere where all life on earth takes place. The biosphere consists of a part of the atmosphere, of a part of the crust of the earth, of the lithosphere and of nearly the whole hydrosphere. In different ecosystems as, e.g., woodlands, rivers, lakes, deserts, oceans, or the deep sea systems, by exchange processes close correlations exist between the living creatures and their habitat. Radionuclides entering the spheres of existence are involved in this exchange. Those from the habitat can be taken up by the animate one, exchanged within the organisms of an ecosystem or passed through to others. Plants living autotrophically by photosynthesis are at the beginning of the food-chain. In contrast, animals are dependent on heterotrophical organic nourishment. Besides the incorporation of radioactive substances from the inorganic compounds, an exchange or passage, respectively between the organisms has to be taken into account. To finish the circuit, particularly adapted microorganisms exist which are nourished saprophytically by decomposition of organic compounds. In contrast to most chemical substances for which toxicity is commonly related to specific molecular structures, radiotoxicity of the isotopes depends on the radiological characteristics as well as on the molecular structure of the radioactive substance. An alteration of the chemical structure of the molecule comprising a radionuclide does not remove the radionuclide from the environment but merely changes its kinetic behaviour in the biosphere or can lead Sources of environmental radionuclides and recent results in analyses of bioaccumulation. A review Richard Tykva