Radioactive noble gases (e. g., krypton and xenon) and volatile fission prod­ucts (e. g., iodine and cesium) were the main constituents of the radioactive materials released into the atmosphere during the Fukushima accident [24]. Of all the noble gases, krypton-85 has the longest half-life (10.8 years) and

24.2 Potential migration of radionuclides in atmospheric, terrestrial, and aquatic systems [23]. Used with permission from The American Association for the Advancement of Science.

will remain in the atmosphere for a very long time due to its high chemical stability. In general, the inhalation of krypton-85 by animals or humans adversely affects the organs of the respiratory system. However, taking into account that we are naturally exposed to much extensive inhalation of radon and daughter nuclides, and that a considerable amount of krypton-85 has already been accumulated in the air by artificial activity, the effect of krypton-85 by this accident is considered to be limited. Radioactive materi­als containing iodine, cesium and other radionuclides are often carried by air particles and subsequently introduced by wet and dry deposition into the terrestrial environment. Radionuclides behave differently in the ter­restrial environment. Some of them (such as cesium and iodine) are mobile in the environment and can easily be transferred into the water supply and food chain [25] . Other radionuclides have low solubility (such as the acti­nides) and can largely be retained in the soil [26] . The main transfer path­ways of radionuclides in the terrestrial system are shown in Fig. 24.3.

The marine environment was affected by aerosols emitted into the atmos­phere and then deposited on the ocean, as well as by the direct release of seawater used for cooling the reactors. In the future, leaching from contami­nated soils will be the main source of pollution into the marine environ­ment. The mobility of radionuclides transferring between atmospheric, terrestrial, and aquatic systems increases the scope of their adverse influ­ences to a wide variety of living organisms and ecological processes.