A methodology for assessing the maximum expected radon flux from soils in northern Latium (central Italy)

Abstract

Northern Latium (Italy) is an area where the Rn risk rate is potentially high because of the extensive outcropping of Neogene U-rich volcanics and the presence of major active tectonic lineaments. The lack of data on Rn risk rates in that area, which is undergoing major urban and industrial development, has prompted this study. It proposes a methodology to evaluate the maximum potential diffusive Rn flux from soils based on the measurement of (226)Ra, (232)Th and (40)K activities by gamma-ray spectrometry, and the measurement of main soil parameters influencing the Rn emanation. This methodology provides a simple, reliable and low-cost tool for drawing up radon flux maps useful to both public planners and private individuals, who want to operate safely in the study area. The proposed methodology may also be applied to other geographic areas outside the prescribed study area.

Transient to stationary radon ( 220 Rn) emissions from a phonolitic rock exposed to subvolcanic temperatures

“…Coherently, EXP1 shows that 220 Rn monotonically increases by about two orders of magnitude as the temperature increases from 100 to 900°C (figure 4 b ). This behaviour corroborates the strong dependence of Rn diffusion on temperature, leading to transient Rn emissions due to a new value of equilibrium activity concentration [29,59,60]. The change in Rn emission rate ( E in arbitrary units) is positively correlated with the temperature-dependent diffusion coefficient of Rn by a nonlinear Arrhenius equation (where T is expressed in Kelvin; [61–63].…”

The imprint of thermally induced devolatilization phenomena on radon signal: implications for the geochemical survey in volcanic areas

“…3). Consequently, the radon emission rate cannot be interpreted and modelled in the frame of a temperaturedependent diffusion model (Beckman & Balek 2002;Voltaggio et al 2006). In contrast, as TRSN 1 is cooled from 800 to 100 • C, the radon emission monotonically decreases with temperature ( Fig.…”

“…The conductive heat flow may produce thermal gradients in the host rocks from 1100 • C at the contact to 200 • C at a distance of thousands of metres, incorporating several cubic kilometres of the substrate (Bonaccorso et al 2010;Mollo et al 2012;Heap et al 2013). The radon emission from the warm host rock is expected to be controlled by the dependency of the gas diffusion coefficient on temperature (Beckman & Balek 2002;Voltaggio et al 2006). However, poorly consolidated and highly porous volcanic rocks (i.e.…”

Carrier and dilution effects of CO 2 on thoron emissions from a zeolitized tuff exposed to subvolcanic temperatures

“…This environmental radioactivity is determined by three isotopes decaying to daughter nuclides by emitting alpha particles: (i) 222 Rn (radon), a product of 238 U decay series ( 226 Ra is the direct parent nuclide) with half-life of 3.823 days; (ii) 220 Rn (thoron), a product of 232 Th decay series ( 224 Ra is the direct parent nuclide) with half-life of 56 s; and (iii) 219 Rn (actinon), a product of 235 U decay series ( 223 Ra is the direct parent nuclide) with half-life of 4 s. Because of its very short half-life and low activity, 219 Rn is not employed in geochemical exploration. Conversely, 222 Rn and 220 Rn are widely monitored in volcano-tectonic settings, in order to discriminate areas with slow and fast gas transport or shallow and deep radiogenic sources [1][2][3][4][5][6]. A great virtue of 222 Rn- 220 Rn monitoring consists of their different half-lives, in conjunction with an identical geochemical affinity due to negligible isotopic fractionation between heavy radon and thoron isotopes, with mass difference of only 0.01%.…”