Public exposure to hazards associated with natural radioactivity in open-pit mining in Ghana

Abstract

The results of studies carried out on public exposure contribution from naturally occurring radioactive materials (NORMS) in two open-pit mines in the Western and Ashanti regions of Ghana are reported. The studies were carried out under International Atomic Energy Agency-supported Technical Co-operation Project GHA/9/005. Measurements were made on samples of water, soil, ore, mine tailings and air using gamma spectrometry. Solid-state nuclear track detectors were used for radon concentration measurements. Survey was also carried out to determine the ambient gamma dose rate in the vicinity of the mines and surrounding areas. The effective doses due to external gamma irradiation, ingestion of water and inhalation of radon and ore dusts were calculated for the two mines. The average annual effective dose was found to be 0.30 +/- 0.06 mSv. The result was found to be within the levels published by other countries. The study provides a useful information and data for establishing a comprehensive framework to investigate other mines and develop guidelines for monitoring and control of NORMS in the mining industry and the environment as a whole in Ghana.

Assessment of public exposure to naturally occurring radioactive materials from mining and mineral processing activities of Tarkwa Goldmine in Ghana

“…The reported average annual effective dose for the two mines was 0.3 ± 0.06 mSv (Darko et al 2010). Similar studies carried out on different types of mines in other countries have been reported (UNSCEAR 2000).…”

“…The highest absorbed dose rate values of 57.0 and 68.0 nGy h −1 recorded at the soil and water sampling points in Tarkwa Township respectively also compared quite well with the worldwide average value. The results of the study in this mine are also lower than the results of similar studies carried out in other mines in Ghana (Darko et al 2010). Table 4 shows the activity concentrations of 238 U, 232 Th and 40 K in the soil/rock samples as well as the absorbed dose rate and the estimated annual effective doses.…”

“…Table 6 shows the results of the comparison of the mean absorbed dose rate calculated from the soil activity concentrations with the absorbed dose rates measured directly in air at 1 m above the ground in this work to similar studies in Ghana and other countries. The mean absorbed dose rate calculated from the soil concentrations Darko et al (2010) for Ghana value is 30 nGy h −1 whilst that measured directly in air is 40 nGy h −1 . The mean absorbed dose rate measured in air was by 1.3 times higher than that estimated from the soil activity concentrations.…”

“…The Tarkwa area lies within the main gold belt of Ghana that stretches from Axim in the southwest, to Konongo in the northeast (Kortatsi 2004). The total population of the Tarkwa Township is about 80,000 (Kumah 2007) with an estimated population of the District being 236,000 (IFC 2003;Darko et al 2010). In addition there are eight communities dotted around the mines (Table 1).…”

“…A recent study on two mines in Ghana have reported average values for 238 U, 232 Th and 40 K in soil for the two mines as follows 28.7 ± 4.8, 25.4 ± 4.0, 581.8 and 34.5, 20.7, 682.4 Bq kg −1 respectively (Darko et al 2010). The reported average annual effective dose for the two mines was 0.3 ± 0.06 mSv (Darko et al 2010).…”