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The study of the fate and effects of radioactive materials in the environment. It derives its principles from basic ecology and radiation biology.
Responses to radiation stress have consequences for both the individual organism and for the population, community, or ecosystem of which it is a part. When populations or individuals of different species differ in their sensitivities to radiation stress, for example, the species composition of the entire biotic community may be altered as the more radiation-sensitive species are removed or reduced in abundance and are replaced in turn by more resistant species. Such changes have been documented by studies in which natural ecological systems, including grasslands, deserts, and forests, were exposed to varying levels of controlled gamma radiation stress. See Population ecology
Techniques of laboratory toxicology are also available for assessing the responses of free-living animals to exposure to low levels of radioactive contamination in natural environments. This approach uses sentinel animals, which are either tamed, imprinted on the investigator, or equipped with miniature radio transmitters, to permit their periodic relocation and recapture as they forage freely in the food chains of contaminated habitats. When the animals are brought back to the laboratory, their level of radioisotope uptake can be determined and blood or tissue samples taken for analysis. In this way, even subtle changes in deoxyribonucleic acid (DNA) structure can be evaluated over time. These changes may be suggestive of genetic damage by radiation exposure. In some cases, damage caused by a radioactive contaminant may be worsened by the synergestic effects of other forms of environmental contaminants such as heavy metals.
Because of the ease with which they can be detected and quantified in living organisms and their tissues, radioactive materials are often used as tracers. Radioactive tracers can be used to trace food chain pathways or determine the rates at which various processes take place in natural ecological systems. Although most tracer experiments were performed in the past by deliberately introducing a small amount of radioactive tracer into the organism or ecological system to be studied, they now take advantage of naturally tagged environments where trace amounts of various radioactive contaminants were inadvertently released from operating nuclear facilities such as power or production reactors or waste burial grounds.
An important component of radioecology, and one that is closely related to the study of radioactive tracers, is concerned with the assessment and prediction of the movement and concentration of radioactive contaminants in the environment in general, and particularly in food chains that may lead to humans. See Ecology, Food web, Radiation biology
a branch of ecology that studies the concentration and migration of radionuclides in the biosphere and the effect of ionizing radiation on organisms and their populations and communities, or biocenoses. The principles of radio-ecology were formulated by V. I. Vemadskii in the 1920’s in his work on the biogeochemistry of radioactive substances and by the Czech scientists J. Stoklasa and Z. Penkav in their monograph The Biology of Radium and Uranium (1932). Radioecol-ogy became firmly established in the mid-1950’s, after the creation of the nuclear industry and nuclear testing, which resulted in global environmental contamination by radionuclides of strontium, cesium, plutonium, carbon, and other elements.
Radioecology usually deals with very low rates of chronic external and internal irradiation of organisms. Under natural conditions, organisms are subjected to irradiation from natural background radiation (including cosmic rays and the radiation from natural radionuclides of U, Ra, and Th) and also from the radioactive contamination of the biosphere by artificial radionuclides. However, many plants and animals can store radionuclides in their vital organs and tissues, which affects the migration of radionuclides in the biosphere and greatly intensifies internal irradiation. High rates of irradiation that act on the cellular genetic apparatus increase the rate of hereditary variability; even higher rates decrease the viability of organisms and result in the extinction of those populations that are most sensitive to ionizing radiation. The structure of biocenoses is thereby altered and the interaction between the species that occupy these areas is weakened.
The establishment of the patterns underlying these processes is very important for many branches of the economy. Of practical importance are the following problems that are studied by radioecology: the migration of radionuclides in food chains (including those of farm animals and man), the disintegration of ecological relations, the deactivation of farmland and bodies of water contaminated by radionuclides, the exploration for surface deposits of radioactive ores using the radioactivity of indicator plants, and the detection of land and water areas contaminated by artificial radionuclides. The wide range of problems studied by radioecology has led to its subdivision into marine, terrestrial (including forest and agricultural), veterinary (with the related science of radiation hygiene), and freshwater radio-ecology.
The results of radioecological research have greatly influenced the adoption of international conventions regarding nuclear testing limitations and the banning of nuclear weapons in case of war. On the basis of the recommendations of radio-ecologists, industry has developed and introduced closed-cycle cooling systems for nuclear reactors, detectors of radioactive aerosols, and methods for storing and neutralizing radioactive wastes that prevent them from entering the environment.
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A. A. PEREDEL’SKII