Natural Radioactivity Levels in the Pearl River Delta Economic Zone of Guangdong, China

The paper presents the preliminary results of natural radiation measurements in high radiation background areas of the Pearl River Delta Economic Zone (PRDEZ) in Guangdong, China. The results indicated that outdoor absorbed dose rate from cosmic radiation range is 55.7-88.7 nGy/h, and the average is 68.2 nGy/h. Outdoor absorbed dose rate from terrestrial gamma radiation range is 22.6-522 nGy/h, and the average is 137 nGy/h in PRDEZ. The highest absorbed dose rate-522 nGy/h is found in Conghua. Average indoor and outdoor radon level in PRDEZ is 30.5 and 11.2 Bq/m³. Average radon content in water-tap water in 12 cities is 6.2 Bq/L; hot spring water is 120.6 Bq/L. Radon content in soil range is 35820-817180 Bq/m³, and the average is 20146 Bq/m³. Average radionuclide contents of ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K in PRDEZ soil are 137.6, 136.7, 175.3 and 700.7 Bq/kg, respectively. Zhongshan and Taishan County have the highest average ²³²Th contents in soil.