Anthropogenic radioactive sources

Aside from accidents in nuclear facilities (e.g., Chernobyl), the main source of anthropogenic radioactive pollution is probably derived from medical applications. Documented reports of radioactive residue mismanagement indicate that sometimes these substances end up in garbage dumps, with the consequent danger of public exposure. The main radioactive isotopes in medical applications are listed in Table 8.7. 

Two groups of radioactivity sources on the earth are to be distinguished, natural and anthropogenic. Natural sources such as and have been pro-... 

There are in principle two sources for anthropogenic radioactivity in rivers in Sweden, 1954-58 (20%) and 1961-62 (80%), and the Chernobyl accident, 1986. These events are quite distinct in time and by using isotopic ratios and radionuclide ratios the two sources can be distinguished from each other. China and France also conducted nuclear tests during 1960 -1980. 

Anthropogenic radioactive contamination of the marine environment has several sources disposal at sea, discharges to the sea, accidental releases and fallout from nuclear weapon tests and nuclear accidents. In addition, discharge of naturally occurring radioactive materials (NORM) from offshore oil and gas production is a considerable source for contamination. 

Radioactive or stable isotopes of noble gases are also used to determine vertical turbulent diffusion in natural water bodies. For instance, the decay of tritium (3H)— either produced by cosmic rays in the atmosphere or introduced into the hydrosphere by anthropogenic sources—causes the natural stable isotope ratio of helium, 3He/ 4He, to increase. Only if water contacts the atmosphere can the helium ratio be set back to its atmospheric equilibrium value. Thus the combined measurement of the 3H-concentration and the 3He/4He ratio yields information on the so-called water age, that is, the time since the analyzed water was last exposed to the atmosphere (Aeschbach-Hertig et al., 1996). The vertical distribution of water age in lakes and oceans allows us to quantify vertical mixing. 

The third principal component of environmental radioactivity is that due to the activities of humans, the anthropogenic radionuclides. This group of nuclides includes the previously discussed cases of 3H and 14C along with the fission products and the transuranium elements. The primary sources of these nuclides are nuclear weapons tests and nuclear power plant accidents. These events and the gross nuclide releases associated with them are shown in Table 3.1. Except for 14C and... 

The impact of all the sources of radioactivity in the zone of the Arctic coast on the local population has not been assessed reliably enough. It was particularly difficult to separate the natural and anthropogenic components of such an impact. Aibulatov (2000) discussed future research into Russian Arctic radioactive pollution, including... 

The anthropogenic radionuclides of most concern are those produced as fission products from nuclear weapons and nuclear reactors. The most devastating release from the latter source to date resulted from the April 26, 1986, explosion, partial meltdown of the reactor core, and breach of confinement structures by a power reactor at Chernobyl in the Ukraine. This disaster released 5 x 107 Ci of radionuclides from the site, which contaminated large areas of Soviet Ukraine and Byelorussia, as well as areas of Scandinavia, Italy, France, Poland, Turkey, and Greece. Radioactive fission products that are the same or similar to elements involved in life processes can be particularly hazardous. One of these is radioactive iodine, which tends to accumulate in the thyroid gland, which may develop cancer or otherwise be damaged as a result. Radioactive cesium exists as the Cs+ ion and is similar to sodium and potassium in its physiological behavior. Radioactive strontium forms the Sr2+ ion and substitutes for Ca2+, especially in bone. 

Many coastal ecosystems have elevated levels of metals and radionuclides (14). Anthropogenic sources of stable isotopes of metals include sewage disposal plants, electroplating plants, and mining and dredging operations sources of radioactive isotopes include effluents from nuclear power plants and submarines, medical establishments, and uranium ore mining. The pollution from most of these operations results from routine or accidental discharges and are either continuous or episodic. 

Strontium is widely distributed in the earth s crust and oceans. Strontium is released into the atmosphere primarily as a result of natural sources, such as entrainment of dust particles and resuspension of soil. Radioactive strontium is released into the environment as a direct result of anthropogenic activities. Stable strontium can be neither created nor destroyed. However, strontium compounds may transform into other chemical compounds. Radioactive strontium is formed by nuclear reactions. Radioactive decay is the only mechanism for decreasing the concentration of radiostrontium. The half-life of 90Sr is 29 years. 

There are essentially three sources of radioactive elements. Primordial nuclides are radioactive elements whose half-lives are comparable to the age of our solar system and were present at the formation of Earth. These nuclides are generally referred to as naturally occurring radioactivity and are derived from the radioactive decay of thorium and uranium. Cosmogenic nuclides are atoms that are constantly being synthesized from the bombardment of planetary surfaces by cosmic particles (primarily protons ejected from the Sun), and are also considered natural in their origin. The third source of radioactive nuclides is termed anthropogenic and results from human activity in the production of nuclear power, nuclear weapons, or through the use of particle accelerators. 

In the analysis of a sarrqrle for its content of natural radioactivity it is necessart today to consider the possibility that the saitqrle has become contaminated by "non-rmtural" radioactivities, i.e. radionuclides added to by human activities (so-called anthropogenic sources). Nuclear weapons tests, nuclear satellites bumt-up in the atmosphere, and nuclear power accidents may release large amounts of activities, see Table 5.4. The nuclear power industry is permitted by health authorities to continually release small, controlled amounts of specified radionuclides into the atmosphere and into open waters. Tables 19.7 and 21.10. 

Tracers serve as a dye with which to follow the circulation of ocean waters. There are conventional ocean tracers such as temperature, salinity, oxygen, and nutrients. There are stable isotope tracers such as oxygen-18, carbon-13, and there are radioactive tracers both naturally occurring (such as the uranium/thorium series, and radium), and those produced both naturally and by the bomb tests (such as tritium and carbon-14). The bomb contributions from the latter two are called transient tracers, as are the CFCs, because they have been in the atmosphere for a short time. This implies an anthropogenic source and a nonsteady input function. 

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