Soil As a Source of Indoor 220Rn

Abstract

Two suggestions for sources of indoor 220Rn (thoron) have appeared in the literature: 1) building materials and outside air, and 2) soil beneath the house. Due to the difficulty of 220Rn measurement and limited data, both suggestions lack sufficient supporting evidence. We have investigated sources of indoor 220Rn in seven occupied houses in northern New Mexico, U.S. A two-filter system was used to measure indoor 220Rn levels continuously, and 220Rn progeny were measured with single filters and specialized alpha-track detectors. The amount of 220Rn entry from soil was curtailed by cutting off soil gas flow to the indoor air with subfloor depressurization mitigation systems. Four of the houses showed significant reductions in 220Rn with mitigation systems on. The average effect for these houses was to reduce indoor 220Rn levels by 70%. The other three houses had no clear reductions but in one of these houses, the mitigation system was not effective for stopping soil gas flow. Our results provide some of the most clear evidence to date supporting soil as an important source of indoor 220Rn.

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

“…Actually, the indoor Rn activity is not only composed of 222 Rn but also of 220 Rn (thoron) released from the soil and building materials (Li, Schery, & Turk, 1992). In the present study, the high diffusive thoron fluxes calculated by Eq.…”

Thoron in indoor air: modeling for a better exposure estimate

“…mudbrick dwellings) is the building material and thus a part of the building, the exhalation of thoron is an essential part of the model. In certain house types, advective transport into the indoor air must be considered as well (Li et al., 1992) despite the short half‐life of 55.6 s. Thoron will not spread homogeneously inside a room but will feature a spatial distribution, which is governed by its diffusive and advective transport from the walls, because of its short half‐life (Shang et al., 2008). Thus, local concentrations do not represent the average concentration in a room.…”

“…mudbrick dwellings) is the building material and thus a part of the building, the exhalation of thoron is an essential part of the model. In certain house types, advective transport into the indoor air must be considered as well (Li et al., 1992) despite the short half‐life of 55.6 s.…”

Analysis of temperature influences on the amplitude–frequency characteristics of Rn gas concentration

“…where F 1 is the function of Rn emanation from the soil (including the influence of external temperature) (Gaso et al, 1994;Hoyos et al, 1998;Iakovleva and Ryzhakova, 2003;Li et al, 1992;Przylibski, 1999;Stranden et al, 1984;Zmazek et al, 2005); F 2 is the daily variation of Rn due to vertical warm convection arising shortly after sunrise (Mishel, 1987); F 3 is the variation of Rn due to rain and Rn dissolved in underground water (Mishel, 1987;Provost et al, 2004;Richon et al, 2005); F 4 is the variation of Rn due to fluctuations in atmospheric pressure (Clements and Wilkening, 1974;Dowell et al, 1991;Hoyos et al, 1998;Garavaglia et al, 1999;Iakovleva and Ryzhakova, 2003;Washington and Rose, 1990;Zimmer and Erzinger, 2003); F 5 is the variation of Rn due to air movement (direction and speed of wind or ventilation) (Dueñas et al, 1999;Garcia-Talavera et al, 2001;Lee and Yu, 2000;Scott, 1992); F 6 is the variation of Rn related to deep geodynamics, especially that arising near earthquake epicenters (Atkinson, 1981;Bolt, 1993;Maeda and Yoshida, 1990); F 7 is the variation of Rn due to strong geomagnetic storms in periods of solar chromo spherical bursts (Semi-Zade, 1978, 1992; F 8 is the variation of Rn, caused by the settling of aerosols following dust storms, which can transfer a number of radioactive elements (Ganor et al, 1991;Mamane et al, 1980) and may lead to a sharp increase of radon.…”

“…Analysis of the literature (Asada, 1982;Atkinson, 1981;Bolt, 1993;Clements and Wilkening, 1974;Cothern, 1987;Dowell et al, 1991;Ganor et al, 1991;Garavaglia et al, 1999;Gaso et al, 1994;Hafez and Hussein, 2001;Hoyos et al, 1998;Lee and Yu, 2000;Mamane et al, 1980;Mishel, 1987;Maeda and Yoshida, 1990;Monnin and Seidel, 1992;Khan, 1993;Li et al, 1992;Richon et al, 2005;Scott, 1992;Sanchez-Moral et al, 1999;Segovia et al, 1995;Semi-Zade, 1978, 1992Singh et al, 2005;Stranden et al, 1984;Virk and Sing, 1993;Washington and Rose, 1990;Wakita, 1996;Wilkening and Watkins, 1976;Zmazek et al, 2005) allowed us to conclude that the observed total concentration of Rn gas (F sum ) can be presented as a sum of eight factors. Every factor has a separate origin and may create a wide range of anomalies .…”