Natural radioactivity and dose assessment in surface soil from Guangdong, a high background radiation province in China

Abstract

Guangdong province has been renown for its high natural background radiation in the world. In this study, the activity concentrations of naturally occurring radionuclides (NORs) 238U, 232Th, 226Ra, and 40K were measured using a High Purity Germanium (HPGe) detector-based gamma spectrometry system on 490 surface soil samples collected from across this province. The concentration of radionuclides ranged from 12.0 to 264.3 Bq/kg for 238U with an average of 79.3 Bq/kg, from 10.3 to 376.0 Bq/kg for 232Th with an average of 101.0 Bq/kg, from 7.6 to 298.3 Bq/kg for 226Ra with an average of 75.1 Bq/kg, and from 8.2 to 1747.1 Bq/kg for 40K with an average of 535.8 Bq/kg, respectively. The mean values of radium equivalent activity (Raeq) and external hazard index (Hex) for the soil samples in the study area were calculated to be 260.8 (28.3–850.3) Bq/kg and 0.70 (0.08–2.30), respectively. The gamma absorbed dose rates (D) in air range from 13.6 to 381.5 nGy/h, with an arithmetic average of 120.0 nGy/h, while the annual effective dose rates (AEDR) were determined to range from 16.7 to 467.8 μSv/y, with an arithmetic average of 147.2 μSv/y. The spatial distribution of calculated Raeq, Hex, D in air and AEDR according to the distribution patterns of NORs was contrasted by the mean of the international values and previous studies on the area. This study provides the essential information on the levels of background radiation in Guangdong.