ABSTRACT
T he exposures of people and other organisms to radiation from many of the sources discussed in Chapter 1 are dependent on how the radioactive contaminants are trans-
ported from the source to the organism. Because most radionuclides are released into the atmosphere, the transfer chain usually starts there. However, large amounts of radionuclides may also be released into the environment via inland waterways or the sea. Radionuclides released into the atmosphere follow the movement of the air before being deposited on the ground by precipitation or various dry deposition mechanisms. Some of these radionuclides will find their way into rivers, lakes or the sea through run-off from the ground or by direct deposition onto the water surface. Radioactive material deposited on the surface environment may subsequently be transported to other parts of the ecosystem. In order to quantify the exposure resulting from a particular release of radioactive elements it is therefore important to understand the physical and chemical processes that govern how these elements are transported in the atmosphere, in water and in ecosystems. This is the subject of this chapter.
