Abstract
The present work is the first systematic and large scale study on radioactive materials and heavy metals in surface soil around the Bayanwula prospective uranium mining area in China. In this work, both natural and anthropogenic radionuclides and heavy metals in 48 surface soil samples were analyzed using High Purity Germanium (HPGe) γ spectrometry and inductively coupled plasma-mass spectrometry (ICP-MS). The obtained mean activity concentrations of 238U, 226Ra, 232Th, 40K, and 137Cs were 25.81 ± 9.58, 24.85 ± 2.77, 29.40 ± 3.14, 923.0 ± 47.2, and 5.64 ± 4.56 Bq/kg, respectively. The estimated average absorbed dose rate and annual effective dose rate were 76.7 ± 3.1 nGy/h and 83.1 ± 3.8 μSv, respectively. The radium equivalent activity, external hazard index, and internal hazard index were also calculated, and their mean values were within the acceptable limits. The estimated lifetime cancer risk was 3.2 × 10−4/Sv. The heavy metal contents of Cr, Ni, Cu, Zn, As, Cd, and Pb from the surface soil samples were measured and their health risks were then assessed. The concentrations of all heavy metals were much lower than the average backgrounds in China except for lead which was about three times higher than that of China’s mean. The non-cancer and cancer risks from the heavy metals were estimated, which are all within the acceptable ranges. In addition, the correlations between the radionuclides and the heavy metals in surface soil samples were determined by the Pearson linear coefficient. Strong positive correlations between radionuclides and the heavy metals at the 0.01 significance level were found. In conclusion, the contents of radionuclides and heavy metals in surface soil around the Bayanwula prospective uranium mining area are at a normal level.
Highlights
Radiation exposure and heavy metal pollution around uranium mining areas have captured worldwide public attention for several decades [1–4]
The activity concentration of 137 Cs was 5.64 Bq/kg, which was the anthropogenic radionuclide from nuclear weapon tests or nuclear power accidents
The calculated mean outdoor γ dose rates was 76.7 nGy·h−1, which was higher than the world average of 60 nGy/h [6] and the Chinese mean value of 62.8 nGy/h [26]
Summary
Radiation exposure and heavy metal pollution around uranium mining areas have captured worldwide public attention for several decades [1–4]. The intensive uranium exploitation and the inappropriate management of the residues have had a harmful impact on the environment [4–6]. The dose contribution from technologically enhanced naturally occurring radioactive materials is increasing [7,8]. The worldwide annual effective dose to the public from natural radiation exposure is 2.4 mSv [9], while it is 3.1 mSv in China, which increased from 2.3 mSv in 1990s [10–12]. Res. Public Health 2017, 14, 300; doi:10.3390/ijerph14030300 www.mdpi.com/journal/ijerph
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