The characteristics of radon and thoron concentration from soil gas in Shenzhen City of Southern China

Abstract

Radon (222Rn) and thoron (220Rn) from soil gas are very significant factors that can affect the indoor radon level in the first floor or in the basement. China is one of the countries with the highest thorium content in the world. Therefore, it is very significant to study 222Rn/220Rn concentration in the soil in Shenzhen City (SC). A 222Rn/220Rn survey was performed using a portable radon monitor (model RAD7) at 69 sites, covered a total area of 1800 km2 in 2013 to get the original data for radon risk estimation in SC. The average values of 222Rn and 220Rn concentration of soil gas of the total 69 locations are 86 ± 72 kBq·m−3 and 118 ± 85 kBq·m−3, respectively. 222Rn/220Rn concentrations are related to geological lithology. 222Rn concentrations vary from 40 to 370 kBq·m−3 and from 15 to 118 kBq·m−3 in weathered granite products and sediments, respectively, while 220Rn concentrations are from 103 to 435 kBq·m−3 and 2.2 to 96 kBq·m−3. The higher 220Rn values were mainly observed at the sites covered by the weathered granite products. Comparing with the areas of high 222Rn concentration, the areas of high 220Rn values are larger. The distribution of 222Rn concentration in the vertical direction displays an exponential distribution mode, but there is no rule of 220Rn concentration. The investigation suggests that people should pay attention to 220Rn contribution in the radon mapping of SC, as well as in the indoor radon survey.

222Rn and 220Rn concentrations in soil gas of the Izera Massif (Sudetes, Poland) as a function of sampling depth

“…Lo ca tion 15, how ever, gave compa ra ble p val ues (within un cer tain ties). Wang et al (2016) re ported av er age 222 Rn and 220 Rn concen tra tions of 130 and 188 kBq m -3 , re spec tively, at a depth of 80 cm in soils de vel oped on weath ered gran ite (S China). These val ues ex ceeded those ob tained in our work at lo cations 4 and 15.…”

“…For se lected sites in the in ves ti gated area, the au thors showed an al most ex act log a rith mic in crease of 222 Rn con cen tra tions with sam pling depths from 20 to 160 cm at inter vals of 20 cm. No rule was ob served for the 220 Rn con centra tions (Wang et al, 2016). Almayahi et al (2013) ob tained ra don and thoron con cen tra tions at a depth of 50 cm in Northern Pen in su lar Ma lay sia that ranged from 134 Bq m -3 to 143 kBq m -3 , and 55 to 423 Bq m -3 , re spec tively.…”

Characteristics of Indoor and Soil Gas Radon, and Discussion on High Radon Potential in Urumqi, Xinjiang, NW China

“…In the investigation of radon in soil gas, the RAD7 was set to sniff mode with a sampling time of 3 min. The soil gas sampling depth was 80 cm below the ground, and the hole was sealed with soil [32,33].…”