Radiochemistry

Main decay modes

All radioisotopes are unstable elements—undergo nuclear decay and emit some form of radiation. The radiation emitted can be one of three types, called alpha, beta, or gamma radiation.

1. α (alpha) radiation - the emission of an atomic number will decrease by 2.

2. β (beta) radiation - the transmutation of a proton. After this happens, the electron is emitted from the nucleus into the electron cloud.

3. gamma radiation - the emission of radioactive decay.

These three types of radiation can distinguished by their difference in penetrating power.

Alpha can be stopped quite easily by a few centimetres in air or a piece of paper and is equivalent to a helium nucleus. Beta can be cut off by an aluminium sheet just a few millimetres thick and are electrons. Gamma is the most penetrating of the three and is a massless chargeless high energy barium-based) to reduce its intensity.

Activation analysis

By arsenic content.^[1]

A series of different experimental methods exist, these have been designed to enable the measurement of a range of different elements in different matrices. To reduce the effect of the matrix it is common to use the chemical extraction of the wanted element and/or to allow the radioactivity due to the matrix elements to decay before the measurement of the radioactivity. Since the matrix effect can be corrected for by observing the decay spectrum, little or no sample preparation is required for some samples, making neutron activation analysis less susceptible to contamination.

The effects of a series of different cooling times can be seen if a hypothetical sample which contains sodium, uranium and cobalt in a 100:10:1 ratio was subjected to a very short pulse of thermal neutrons. The initial radioactivity would be dominated by the ²⁴Na activity but with increasing time the ²³⁹Np and finally the ⁶⁰Co activity would predominate.

Biochemical uses

One biological application is the study of phosphorus-32. In these experiments stable phosphorus is replaced by the chemical identical radioactive P-32, and the resulting radioactivity is used in analysis of the molecules and their behaviour.

Another example is the work which was done on the methylation of elements such as sulfur work the isotope ³⁵S was used, while for polonium ²⁰⁷Po was used. In some related work by the addition of ⁵⁷Co to the bacterial culture, followed by isolation of the cobalamin from the bacteria (and the measurement of the radioactivity of the isolated cobalamin) it was shown that the bacteria convert available cobalt into methylcobalamin.

Environmental

Radiochemistry also includes the study of the behaviour of radioisotopes in the environment; for instance, a forest or grass fire can make radioisotopes become mobile again.^[4] In these experiments, fires were started in the exclusion zone around Chernobyl and the radioactivity in the air downwind was measured.

It is important to note that a vast number of processes are able to release radioactivity into the environment, for example the action of cosmic rays on the air is responsible for the formation of radioisotopes (such as ¹⁴C and ³²P), the decay of ²²⁶Ra forms ²²²Rn which is a gas which can diffuse through rocks before entering buildings^[5][6][7] and dissolve in water and thus enter drinking water^[8] in addition human activities such as bomb tests, accidents,^[9] and normal releases from industry have resulted in the release of radioactivity.

Chemical form of the actinides

The environmental chemistry of some radioactive elements such as plutonium is complicated by the fact that solutions of this element can undergo XANES.^[14][3][4]

Movement of colloids

It is important to note that while binding of a metal to the surfaces of the soil particles can prevent its movement through a layer of soil, it is possible for the particles of soil which bear the radioactive metal can migrate as colloidal particles through soil. This has been shown to occur using soil particles labeled with ¹³⁴Cs, these have been shown to be able to move through cracks in the soil.^[15]

Normal background

It is important to note that radioactivity is present everywhere (and has been since the formation of the earth). According to the International Atomic Energy Agency, one kilogram of soil typically contains the following amounts of the following three natural radioisotopes 370 Bq ⁴⁰K (typical range 100-700 Bq), 25 Bq ²²⁶Ra (typical range 10-50 Bq), 25 Bq ²³⁸U (typical range 10-50 Bq) and 25 Bq ²³²Th (typical range 7-50 Bq).^[16]

Action of microorganisms

The action of microorganisms can fix uranium; Thermoanaerobacter can use uraninite (UO₂).^[17] Other researchers have also worked on the fixing of uranium using bacteria[5][6][7], Francis R. Livens et al. (Working at Manchester) have suggested that the reason why Geobacter sulfurreducens can reduce UO₂²⁺ carions to uranium dixoide is that the bacteria reduce the uranyl cations to UO₂⁺ which then undergoes disproportionation to form UO₂²⁺ and UO₂. This reasoning was based (at least in part) on the observation that NpO₂⁺ is not converted to an insoluble neptunium oxide by the bacteria.^[18]

References

1. ^ H. SMITH, S. FORSHUFVUD & A. WASSÉN, Nature, 1962, 194(26 May), 725-726
2. ^ N. Momoshima, Li-X. Song, S. Osaki and Y. Maeda, "Biologically induced Po emission from fresh water", Journal of Environmental Radioactivity, 2002, 63, 187-197
3. ^ N. Momoshima, Li-X. Song, S. Osaki and Y. Maeda, "Formation and emission of volatile polonium compound by microbial activity and polonium methylation with methylcobalamin", Environmental Science and Technology, 2001, 35, 2956-2960
4. ^ Yoschenko VI et al (2006) Resuspension and redistribution of radionuclides during grassland and forest fires in the Chernobyl exclusion zone: part I. Fire experiments J Envir Radioact 86:143-63 PMID 16213067
5. ^ Janja Vaupotič and Ivan Kobal, "Effective doses in schools based on nanosize radon progeny aerosols", Atmospheric Environment, 2006, 40, 7494-7507
6. ^ Michael Durand, Building and Environment, "Indoor air pollution caused by geothermal gases", 2006, 41, 1607-1610
7. ^ Paolo Boffetta, "Human cancer from environmental pollutants: The epidemiological evidence", Mutation Research/Genetic Toxicology and Environmental Mutagenesis, 2006, 608, 157-162
8. ^ M. Forte, R. Rusconi, M.T. Cazzaniga and G. Sgorbati, "The measurement of radioactivity in Italian drinking waters", Microchemical Journal, 2007, 85, 98-102
9. ^ R. Pöllänen, M.E. Ketterer, S. Lehto, M. Hokkanen, T.K. Ikäheimonen, T. Siiskonen, M. Moring, M.P. Rubio Montero and A. Martín Sánchez, "Multi-technique characterization of a nuclearbomb particle from the Palomares accident", Journal of Environmental Radioactivity, 2006, 90, 15-28
10. ^ Rabideau, S.W., Journal of the American Chemical Society, 1957, 79, 6350-6353
11. ^ P. G. Allen, J. J. Bucher, D. K. Shuh, N. M. Edelstein, and T. Reich, "Investigation of Aquo and Chloro Complexes of UO22+, NpO2+, Np4+, and Pu3+ by X-ray Absorption Fine Structure Spectroscopy ", Inorganic Chemistry, 1997, 36, 4676-4683
12. ^ David L. Clark, Steven D. Conradson, D. Webster Keogh Phillip D. Palmer Brian L. Scott and C. Drew Tait, "Identification of the Limiting Species in the Plutonium(IV) Carbonate System. Solid State and Solution Molecular Structure of the [Pu(CO3)5]6- Ion", Inorganic Chemistry, 1998, 37, 2893-2899
13. ^ Jörg Rothe, Clemens Walther, Melissa A. Denecke, and Th. Fanghänel, "XAFS and LIBD Investigation of the Formation and Structure of Colloidal Pu(IV) Hydrolysis Products ", Inorganic Chemistry, 2004, 43, 4708-4718
14. ^ M. C. Duff, D. B. Hunter, I. R. Triay, P. M. Bertsch, D. T. Reed, S. R. Sutton, G. Shea-McCarthy, J. Kitten, P. Eng, S. J. Chipera, and D. T. Vaniman, "Mineral Associations and Average Oxidation States of Sorbed Pu on Tuff", Environ. Sci. Technol, 1999, 33, 2163-2169
15. ^ R.D. Whicker and S.A. Ibrahim, "Vertical migration of 134Cs bearing soil particles in arid soils: implications for plutonium redistribution", Journal of Environmental Radioactivity, 2006, 88, 171-188.
16. ^ Generic Procedures for Assessment and Response during a Radiological Emergency, International Atomic Energy Agency TECDOC Series number 1162, published in 2000 [1]
17. ^ Yul Roh, Shi V. Liu, Guangshan Li, Heshu Huang, Tommy J. Phelps, and Jizhong Zhou, "Isolation and Characterization of Metal-Reducing Thermoanaerobacter Strains from Deep Subsurface Environments of the Piceance Basin, Colorado", Applied and Environmental Microbiology, 2002, 68, 6013-6020.
18. ^ Joanna C. Renshaw, Laura J. C. Butchins, Francis R. Livens, Iain May, John M. Charnock, and Jonathan R. Lloyd, Environ. Sci. Technol., 2005, 39(15), 5657-5660.