Radium species

Baskaran et al. [856] have discussed the rapid extraction and determination of thorium, lead, and radium species from large volumes of seawater. 

Table 7.27 Literature thermodynamic data for radium species at 25 °C. ...

Radium, like most other group II metals, is soluble in seawater. Formation of Ra and Ra by decay of Th in marine sediments leads to release of these nuclides from the sediment into the deep ocean. Lead, in contrast, is insoluble. It is found as a carbonate or dichloride species in seawater (Byrne 1981) and adheres to settling particles to be removed to the seafloor. 

McKee BA, DeMaster DJ, Nittrouer CA (1986b) The use of " Th/ U disequilibrium to examine the fate of particle-reactive species on the Yangtze continental. Shelf. Earth Planet Sci Lett 68 431-442 McKee BA, DeMaster DJ, Nittrouer CA (1987) Uranium geochemistry on the Amazon shelf evidence for uranium release from bottom sediments. Geochim Cosmochim Acta 51 2779-2786 Miller RJ, Kraemer, TF, McPherson BF (1990) Radium and radon in Charlotte Harbor estuaiy, Florida. Estuar Coastal Shelf Sci 31 439-457... 

Baskaran et al. [30] pumped seawater at 35l/min and collected dissolved species on cartridges prior to determining radium, thorium, and lead by y counting methods. 

In the environment, thorium and its compounds do not degrade or mineralize like many organic compounds, but instead speciate into different chemical compounds and form radioactive decay products. Analytical methods for the quantification of radioactive decay products, such as radium, radon, polonium and lead are available. However, the decay products of thorium are rarely analyzed in environmental samples. Since radon-220 (thoron, a decay product of thorium-232) is a gas, determination of thoron decay products in some environmental samples may be simpler, and their concentrations may be used as an indirect measure of the parent compound in the environment if a secular equilibrium is reached between thorium-232 and all its decay products. There are few analytical methods that will allow quantification of the speciation products formed as a result of environmental interactions of thorium (e.g., formation of complex). A knowledge of the environmental transformation processes of thorium and the compounds formed as a result is important in the understanding of their transport in environmental media. For example, in aquatic media, formation of soluble complexes will increase thorium mobility, whereas formation of insoluble species will enhance its incorporation into the sediment and limit its mobility. 

A radioactive element is an element that disintegrates spontaneously with the emission of various rays and particles. Most commonly, the term denotes radioactive elements such as radium, radon (emanation), thorium, promethium, uranium, which occupy a definite place in the periodic table because of their atomic number. The term radioactive element is also applied to the various other nuclear species, (which arc produced by the disintegration of radium, uranium, etc.) including (he members of the uranium, actinium, thorium, and neptunium families of radioactive elements, which differ markedly in their stability, and are isotopes of elements from thallium (atomic number 81) to uranium (atomic number... 

In experimental animals, bone cancer has been the most prominent consequence of radium incorporation and has been found in all species tested. 

Comparative Toxicokinetics. There are currently not enough data to evaluate any potential species-related differences in response to radium exposure by any route. It would be useful to have information on which animal models most closely approximate humans in this regard in order to help interpret the relevance to humans of any toxicity findings in animal studies. Studies on the toxicokinetics of radium following inhalation, oral, and dermal exposure are needed to compare the different routes of exposure. 

The standard used for measuring the activity of radioactive species is the ctirie it is the activity of 1 g of radium, for which A 226 and tj 1622 years. It represents 3.7 xlO disintegrations per second. 

In water and sediments, the time to chemical steady-states is controlled by the magnitude of transport mechanisms (diffusion, advection), transport distances, and reaction rates of chemical species. When advection (water flow, rate of sedimentation) is weak, diffusion controls the solute dispersal and, hence, the time to steady-state. Models of transient and stationary states include transport of conservative chemical species in two- and three-layer lakes, transport of salt between brine layers in the Dead Sea, oxygen and radium-226 in the oceanic water column, and reacting and conservative species in sediment. 

Radium-226 in Water. Ra-226 will be considered as an example of a chemical species which is being removed from the oceanic water column by a first-order chemical reaction, radioactive decay. Other possible mechanisms of removal, such as uptake by detrital silicates and organisms, will not be discussed. The supply of Ra-226, however, from organic matter decomposing in the water column will be considered. 

Radon is a gas-specie that is formed by the solid radioactive element radium there is found all over in the earth in different amounts. Radon is radioactive and can be found in measurable amounts in our houses typically in the cellar. Radon penetrates into building primarily through the underground through cracks in the building fundament. 

Alpha radioactivity is found principally among elements beyond bismuth in the periodic table. AH the nuclides important as fissionable or fertile material are alpha emitters, with half-lives and decay energies given in Table 2.1. These half-lives are so long that depletion of these fuel species by radioactive decay is not important, but all these nuclides are toxic, especially plutonium, which is even more toxic than radium. 

In the steady state of radioactive equilibrium equal numbers of a-particles are emitted by each of the four species radium, radon, radium A, and radium C. Rutherford and Geiger (Proc. Roy. Soc. A. 1908, 81, 141) isolated a concentrated source consisting of a mixture of radium A, radium B, radium C, and radium C. After a quarter of an hour the radiation due to radium A has become negligible and all the a-activity is then due to the radium C in radioactive equilibrium with the radium C. Furthermore, of the species mentioned, radium C alone emits penetrating y-rays and so measurement of the intensity of this... 

The hypothesis got some support fi-om the fact that the activity coprecipitated from the solution of irradiated uranium with a precipitate of salts of added barium — the lighter homologue of radium. Hahn and coworkers used a coprecipitation with barium chloride from a solution of concentrated hydrochloric acid. Under these conditions, the BaCl2 precipitate is very clean and one could conclude that a radioactive species coprecipitated would have to be an element belonging to the group of alkaline earths, namely Sr, Ba, or Ra. Since barium... 

Many individual components in the series are referred to by names derived from their positions in the series and other details that are no longer of much interest except to reveal the history of discovery of structure of each series. The most common names of this type for the Th series are given in O Fig. 13.1. Since Ra and Ac are sandwiched between two isotopes of thorium, they were called mesothorium 1 and 2 meso intermediate or in the middle), with symbols MsThi and MsTh2- Th has higher specific activity (activity per unit mass) than Th and was called radiothorium (RdTh). Tn ( Rn) is short for thoron, the gaseous component similar to radon from radium. Relatively simple chemical procedures could show that there were three species following Tn, and these were named... 

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