Airborne radioactive materials and plants: a review

Airborne radioactive materials readily contaminate plant surfaces and thus are incorporated into the food chains. Most of the nuclear fission products and naturally occurring radionuclides in the air are carried on solid particles ranging in size from a few submicrons to several millimetres in diameter. Of many available mechanisms, rainfall plays a dominant role in the deposition and removal of radioactive particles from plants. Mechanisms for the deposition of submicron particles, which carry significant amounts of radioactivity, are still not very well understood. Available information on the physicochemical aspects of the retention of radionuclides by plants is inadequate in explaining radionuclide uptake and desorbability. Much of the work reported so far has been carried out on selected fission products only. There is a dearth of data pertaining to naturally occurring radionuclides, especially 222Rn and its daughters, significant amounts of which are released to the environment during uranium mining and milling operations. Radiation damage in plants is difficult to detect except at levels of contamination thousands of times higher than those attained in most real life situations. Existing reports five conflicting accounts of the damage induced by low-level radiation in plants. The literature data discussed in this review are presented as basic information needed for the conduct and interpretation of useful research.