Radium adsorbed

Figure 2. Alpha spectrum for a radium adsorbing manganese-oxide thin film exposed to a groundwater sample, after Surbeck (2000) and Eikenberg et al. (2001b). A 2x2 cm sheet is exposed to O.l-l.O L of sample for 2 days, capturing nearly all of the radium in the sample. These sample discs can be used directly for low-level alpha spectrometry without the need for further separation and preparation methods to produce planar sample sources. Energy resolution is nearly as good as for electroplated sources, and detection limits are typically 0.2 mBqA (6 fg Ra/L) for Ra and " Ra for a one-week counting period. These sensitivities are comparable to traditional methods of alpha spectrometry. [Used by permission of Elsevier Science, from Eikenberg et al. (2001), J Environ Radioact, Vol. 54, Fig. 4, p. 117]...

Tsezos, M., Baird, M. H. I. Shemilt, L. W. (1987). The elution of radium adsorbed by microbial biomass. The Chemical Engineering Journal, 34, B57-B64. 

The thoron source is made from acrylic fiber impregnated with Mn02 which is used as a thorium/radium adsorber. There are two closed air loops (1) circulating through the exchanger driven by an external air pump and (2) a separate loop between the RAD-7 and the primary air path driven by the internal pump of the RAD- 7. 

Radium adsorbed on surfaces of clay-silt particles and capillaries and microfractures of rocks is a significant source of Rn in soil gases, U mines and groundwaters. 

Keywords constructed wetlands, passive biological water treatment, adsorbents, uranium, radium, arsenic, iron, manganese... 

Tsezos, M. Keller, D. M. (1983). Adsorption of radium-226 by biological origin adsorbents. Biotechnology and Bioengineering, 25, 201-15. 

Radium may be transported in the atmosphere in association with particulate matter. It exists primarily as a divalent ion in water, and its concentration is usually controlled by adsorption-desorption mechanisms at solid-liquid interfaces and by the solubility of radium-containing minerals. Radium does not degrade in water other than by radioactive decay at rates that are specific to each isotope. Radium may be readily adsorbed by earth materials consequently, it is usually not a mobile constituent in the environment. It may be bioconcentrated and bioaccumulated by plants and animals, and it is transferred in food chains from lower trophic levels to humans. 

No data were located on the residence time of radium in the atmosphere or its deposition rate. However, data for other elements adsorbed to particulate matter indicate that the residence time for fine particles is about 1 to 10 days (EPA 1982b Keitz 1980). Radium may, therefore, be subject to long-range transport in the atmosphere. 

Radium in water may be readily adsorbed by sediments, soils, and aquifer components. It has been experimentally demonstrated that radium can be adsorbed by soils and sediments (Benes and Strejc 1986 Landa and Reid 1982), ferric hydroxide and quartz (Benes et al. 1984 Valentine et al. 1987), kaolinite and montmorillonite (Benes et al. 1985), and muscovite and albite (Benes et al. 1986). 

Hence, once adsorbed, radium may be partially resistant to removal, which would further reduce the potential for environmental release and human exposure. 

Clifford D, Vijjeswarapu W, Subramonian S. 1988. Evaluating various adsorbents and membranes for removing radium from groundwater. J AWWA (July) 94-104. 

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