Actinides in the environment
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Inhalation versus ingestion
Generally,
Ingested low-fired oxides and soluble salts such as nitrate can be absorbed into the blood stream. If they are inhaled then it is possible for the solid to dissolve and leave the lungs. Hence, the dose to the lungs will be lower for the soluble form.
Actinium
Thorium
In India, a large amount of thorium ore can be found in the form of monazite in placer deposits of the Western and Eastern coastal dune sands, particularly in the Tamil Nadu coastal areas. The residents of this area are exposed to a naturally occurring radiation dose ten times higher than the worldwide average.[2]
Occurrence
Thorium is found at low levels in most rocks and
Effects in humans
Thorium has been linked to liver cancer. In the past, thoria (thorium dioxide) was used as a contrast agent for medical X-ray radiography but its use has been discontinued. It was sold under the name Thorotrast.
Protactinium
Protactinium-231 occurs naturally in uranium ores such as pitchblende, to the extent of 3 ppm in some ores. Protactinium is naturally present in soil, rock, surface water, groundwater, plants and animals in very low concentrations (on the order of 1 ppt or 0.1 picocuries (pCi)/g).
Uranium
Uranium is a natural metal which is widely found. It is present in almost all soils and it is more plentiful than antimony, beryllium, cadmium, gold, mercury, silver, or tungsten, and is about as abundant as arsenic or molybdenum. Significant concentrations of uranium occur in some substances such as phosphate rock deposits, and minerals such as lignite, and monazite sands in uranium-rich ores (it is recovered commercially from these sources).
Seawater contains about 3.3 parts per billion of uranium by weight[4] as uranium (VI) forms soluble carbonate complexes. Extraction of uranium from seawater has been considered as a means of obtaining the element. Because of the very low specific activity of uranium the chemical effects of it upon living things can often outweigh the effects of its radioactivity. Additional uranium has been added to the environment in some locations, from the nuclear fuel cycle and the use of depleted uranium in munitions.
Neptunium
Like plutonium, neptunium has a high affinity for soil.[5] However, it is relatively mobile over the long term, and diffusion of neptunium-237 in groundwater is a major issue in designing a deep geological repository for permanent storage of spent nuclear fuel. 237Np has a half-life of 2.144 million years and is therefore a long-term problem; but its half-life is still much shorter than those of uranium-238, uranium-235, or uranium-236, and 237Np therefore has higher specific activity than those nuclides. It is used only to make plutonium-238 when bombarded with neutrons in a lab.
Plutonium
Sources
Plutonium in the environment has several sources. These include:
- Atomic batteries
- In space
- In pacemakers
- Bomb detonations
- Bomb safety trials
- Nuclear crime
- Nuclear fuel cycle
- Nuclear power plants
Environmental chemistry
Plutonium, like other actinides, readily forms a
- PuO2CO32−
- PuO2(CO3)24−
- PuO2(CO3)36−
PuO2 formed from neutralizing highly acidic nitric acid solutions tends to form polymeric PuO2 which is resistant to complexation. Plutonium also readily shifts valences between the +3, +4, +5 and +6 states. It is common for some fraction of plutonium in solution to exist in all of these states in equilibrium.
Plutonium is known to bind to soil particles very strongly; see above for an X-ray spectroscopic study of plutonium in soil and
Americium
In 1999, a truck transporting 900 smoke detectors in France had been reported to have caught fire; it is claimed that this led to a release of americium into the environment.[8] In the U.S., the "Radioactive Boy Scout" David Hahn was able to buy thousands of smoke detectors at remainder prices and concentrate the americium from them.
There have been cases of humans being exposed to americium. The worst case was that of
The most common isotope americium-241 decays (half-life 432 years) to neptunium-237 which has a much longer half-life, so in the long term, the issues discussed above for neptunium apply.[11]
Americium released into the environment tends to remain in soil and water at relatively shallow depths and may be taken up by animals and plants during growth; shellfish such as shrimp take up americium-241 in their shells, and parts of grain plants can become contaminated with exposure.[12] In a 2021 paper, J.D. Chaplin et al. reported advances in the Diffusive gradients in thin films technique, which have provided a method to measure labile bioavailable Americium in soils, as well as in freshwater and seawater.[13]
Curium
Atmospheric curium compounds are poorly soluble in common solvents and mostly adhere to soil particles. Soil analysis revealed about 4,000 times higher concentration of curium at the sandy soil particles than in water present in the soil pores. An even higher ratio of about 18,000 was measured in loam soils.[14]
Californium
Californium is fairly insoluble in water, but it adheres well to ordinary soil, and concentrations of it in the soil can be 500 times higher than in the water surrounding the soil particles.[15]
See also
- Uranium in the environment
- Radium in the environment
- Background radiation
- Radioecology
References
- .
- ^ "Compendium Of Policy And Statutory Provisions Relating To Exploitation Of Beach Sand Minerals". Government Of India. Archived from the original on 2008-12-04. Retrieved 2008-12-19.
- ^ THORIUM Agency for Toxic Substances and Disease Registry. July 1999.
- ^ "Uranium: the essentials". WebElements. Retrieved 2008-12-19.
- ^ "Neptunium" (PDF). Argonne National Laboratory, EVS. August 2005. Archived from the original (PDF) on 2008-12-19. Retrieved 2008-12-19.
- PMID 16564117.
- .
- ^ "Radiological Agent: Americium-241". CBWInfo.com. Archived from the original on 2009-01-08. Retrieved 2008-12-19.
- PMID 2781271.
- ^ PubChem. "Americium". pubchem.ncbi.nlm.nih.gov. Retrieved 2019-12-13.
- ^ Stoll 2017-10-10T22:55:00Z, Carol (10 October 2017). "Facts About Neptunium". livescience.com. Retrieved 2019-12-13.
{{cite web}}
: CS1 maint: numeric names: authors list (link) - ^ "Public Health Statement for Americium". CDC - ATSDR. Retrieved 11 September 2016.
- S2CID 237307309.
- ^ Human Health Fact Sheet on Curium Archived 2006-02-18 at the Wayback Machine, Los Alamos National Laboratory
- ^ "Human Health Fact Sheet: Californium" (PDF). Argonne National Laboratory. August 2005. Archived from the original (PDF) on July 21, 2011.
- Burakov, B. E.; Ojovan, M. I.; Lee, W. E. (2010). Crystalline Materials for Actinide Immobilisation. London: Imperial College Press. ISBN 978-1-84816-418-5. Archived from the originalon 2012-03-09.
Further reading
- Hala, Jiri, and James D. Navratil. Radioactivity, Ionizing Radiation and Nuclear Energy. Konvoj: Brno, Czech Republic, 2003. ISBN 80-7302-053-X.
External links
- "Why do mechanisms matter in radioactive waste management?" – Royal Society for Chemistry
- "Spectroscopies for Environmental Studies of Actinide Species" – Federation of American Scientists