Natural radioactivity and radon exhalation rate in Brazilian igneous rocks

Departamento de Petrologia e Metalogenia, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, Av. 24-A No. 1515, Rio Claro, São Paulo, Brazil.
Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine (Impact Factor: 1.23). 03/2011; 69(7):1094-9. DOI: 10.1016/j.apradiso.2011.03.004
Source: PubMed


This paper reports the natural radioactivity of Brazilian igneous rocks that are used as dimension stones, following the trend of other studies on the evaluation of the risks to the human health caused by the rocks radioactivity as a consequence of their use as cover indoors. Gamma-ray spectrometry has been utilized to determine the (40)K, (226)Ra and (232)Th activity concentrations in 14 rock types collected at different quarries. The following activity concentration range was found: 12.18-251.90 Bq/kg for (226)Ra, 9.55-347.47 Bq/kg for (232)Th and 407.5-1615.0 Bq/kg for (40)K. Such data were used to estimate Ra(eq), H(ex) and I(γ), which were compared with the threshold limit values recommended in literature. They have been exceeded for Ra(eq) and H(ex) in five samples, where the highest indices corresponded to a rock that suffered a process of ductile-brittle deformation that caused it a microbrecciated shape. The exhalation rate of Rn and daughters has also been determined in slabs consisting of rock pieces ~10 cm-long, 5 cm-wide and 3 cm-thick. It ranged from 0.24 to 3.93 Bq/m(2)/h and exhibited significant correlation with eU (=(226)Ra), as expected. The results indicated that most of the studied rocks did not present risk to human health and may be used indoors, even with low ventilation. On the other hand, igneous rocks that yielded indices above the threshold limit values recommended in literature may be used outdoors without any restriction or indoors with ample ventilation.

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    • "Volcanic tuff stones consisting of consolidated volcanic ash, and large and small pieces ejected from vents during a volcanic eruption, with a porous structure in different colours, are used as covering materials for insulating and ornamental purposes on the exterior and interior of buildings in Turkey. Up until now, several studies on the radiometric, petrographic and mineralogical properties of natural stone samples have been reported (Anjos et al., 2005; Xinwei et al., 2006; El-Arabi, 2007; Asghar et al., 2008; Kitto et al., 2009; Koornneef et al., 2010; Lanzo et al., 2010; Moura et al., 2011; Abd El-Ghafour et al., 2012; Capaccioni et al., 2012; Trevisi et al., 2012; Turhan, 2012). However, according to our literature survey, a comprehensive study related to the radiometric properties of volcanic tuff samples collected from Turkey has not yet been conducted, except one study in which eight volcanic tuff samples were considered (De˘ gerlier, 2013). "

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    • "The new types of building materials are brought from various places around the world, and some may be extracted from areas with high background radiation . The contribution of building materials to indoor radon has been investigated in some previous studies in different regions [5] [6] [7]. "
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    • "and they are widely used in recent publications for presenting the radioactive hazard of building materials (e.g. Al-Sulaiti et al., 2011; Damla et al., 2011; Moura et al., 2011). "
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