Phytoremediation of Radionuclides
Overview of Radionuclides
Overview of Radionuclides
On December 2, 1942 the first controlled fission reaction occurred (Saling and Fentiman 2002). The new technology was rapidly used to create atomic weapons, address medical issues, and eventually develop nuclear power generation. Environmental concerns and current political tension have increased awareness of nuclear power as an alternative to fossil fuels, since no greenhouse gases are created and the United States of America (USA) has relatively abundant supplies of nuclear fuel. A major point of contention over nuclear power generation is the issue of safety and disposal of radioactive waste products. No consensus concerning the long-term storage of radioactive waste has been reached by our society or government.
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Some radionuclides are naturally occurring elements that are distributed in the earth’s crust, these include: Uranium, Radium, Radon, and Thorium (Negri and Hinchman 2000). The nuclear fuel cycle can introduce radioactive isotopes into the environment from mining (222Rn), milling (238U, 230Th, 226Ra, 210Pb), nuclear testing (131I, 90Sr, 137Cs, Pu), and accidents (Entry et al. 1996, Negri and Hinchman 2000). Approximately 2g of uranium are found in every ton of the earth’s crust and mining recovery rates vary between one and five tons of uranium for every 1000 tons of ore (Saling and Fentiman 2002). Two methods are used to acquire the radioactive material: mining and in-situ leaching (solution mining). Both processes cause environmental degradation, but different remediation and restoration methods are required for each extraction technique. Radioactive wastes are classified into five categories to facilitate appropriate management and clean-up: high-level waste (HLW), spent nuclear fuel (SNF), transuranic waste (TRU), low-level waste (LLW), and mill tailings (Saling and Fentiman 2002). The following table lists typical radionuclides that may be found at a remediation site:
Radiation is released after the spontaneous disintegration of atomic nuclei and can be in the form of electromagnetic waves (gamma) or subatomic particles (alpha, beta, neutrons). Ionizing radiation is known to induce cancer and genetic mutations of DNA, although it is also used as a treatment therapy for cancer patients. In the 1890’s Marie and Pierre Curie discovered radium and the radioactive substance was rapidly implemented as a cancer treatment. There are two types of health effects from radiation: somatic and genetic. Somatic effects induce cancerous growth of cells, while genetic effects are manifested in the descendents of exposed subject. (Saling and Fentiman 2002). The initial symptoms due to exposure of greater than 200 rads are nausea, diarrhea, fatigue, vomiting, hemorrhage, loss of hair, inflammation of mouth and throat, and a general loss of energy (Nuclear Regulatory Commission 2008).
