Natural radioactivity levels in topsoil from the Pearl River Delta Zone, Guangdong, China.
Concentrations of the natural radionuclides ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K have been measured by γ-ray spectrometry in 796 topsoil samples from the Pearl River Delta Zone (PRDZ) of Guangdong, China. The mean concentrations for ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K were found to be 140 ± 37 Bq kg⁻¹, 134 ± 41 Bq kg⁻¹, 187 ± 80 Bq kg⁻¹ and 680 ± 203 Bq kg⁻¹ dry mass, respectively. These values were all higher than the mean values in soil for China and the world. Outdoor air-absorbed dose rates, calculated from activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K, ranged from 86 to 237 nGy h⁻¹, with a mean value of 165 ± 46 nGy h⁻¹. The corresponding annual outdoor effective dose rate per person was estimated to be between 0.11 and 0.29 mSv y⁻¹, with a mean value of 0.20 ± 0.06 mSv y⁻¹, which was also higher than the world mean value of 0.07 mSv y⁻¹. The radium equivalent activity (Ra(eq)) and the external hazard index (I(r)) resulted from the natural radionuclides in soil, were also calculated and found to vary from 230 to 676 Bq kg⁻¹ and from 0.6 to 1.8, respectively. The Ra(eq) and the I(r) in all the investigated regions were up to 75% higher than the set limits of 370 Bq kg⁻¹ and 1.0, respectively.
School of Environmental Science & Engineering, Guangzhou University, Guangzhou 510006, PR China.
Gang
G
Song
Diyun
D
Chen
Zeping
Z
Tang
Zhiqiang
Z
Zhang
Wenbiao
W
Xie
D001417:Background Radiation; D002681:China; D011197:Potassium Radioisotopes / Q000032:analysis; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000706:statistics & numerical data*; D011883:Radium / Q000032:analysis; D045483:Rivers; D012987:Soil / Q000032:analysis*; D013051:Spectrometry, Gamma; D013910:Thorium / Q000032:analysis; D014501:Uranium / Q000032:analysis
D011197:Potassium Radioisotopes; D012987:Soil; D014501:Uranium; D013910:Thorium; D011883:Radium