Assessment of natural and anthropogenic radioactivity levels in soils, rocks and water in the vicinity of Chirano Gold Mine in Ghana

Abstract

Studies have been carried out within and around the operational area of the Chirano Gold Mine Ltd of Ghana to ascertain the baseline radioactivity levels of naturally occurring radioactive materials as well as artificial radionuclides in the surface and underground mines. The analysis was carried out by using gamma spectrometry to quantify the radionuclides of interest, namely (238)U, (232)Th, (137)Cs and (40)K in soil, ore, waste rock and water samples. The average activity concentrations of (238)U, (232)Th, (40)K and (137)Cs in the soil/rock samples were 9.79±5.39, 9.18±7.06, 237.40±144.34 and 0.64±0.57 Bq kg(-1), respectively. For the water samples, the average activity concentrations were 0.86±0.67, 0.97±1.33 and 9.05±10.45 Bq l(-1) for (226)Ra, (232)Th and (40)K, respectively. The total annual effective dose to the public was estimated to be 0.13 mSv, which is below the International Commission on Radiological Protection recommended level of 1 mSv for public exposure control. The study also assessed the elemental concentrations of U, Th and K in the soil/rock samples from the gold mine and surrounding communities. The average concentrations of the U, Th and K were 0.82±0.48, 2.18±1.77 µg g(-1) and 0.77±0.47 %, respectively. The concentrations of U, Th and K were variable in soil and rock samples taken from different locations in the study area with values varying in the range 0.28-2.21, 0.24-6.50 µg g(-1) and 0.28-1.87 %, respectively. The concentrations of U, Th and K are far lower than the world average values but comparable with the range of similar studies for different countries. The concentration values of gross-alpha and gross-beta for all the water samples were below the Ghana Standards Authority and World Health Organisation recommended guideline values for drinking water quality. The results obtained in this study also show that radiation levels are within the natural background radiation levels found in the literature and compare well with those of similar studies for other countries including Ghana.

Natural radioactivity levels in soils, rocks and water at a mining concession of Perseus gold mine and surrounding towns in Central Region of Ghana

“…According to UNSCEAR ( 2000 ) report, the worldwide average absorbed dose rate in air measured from terrestrial gamma radiation is 60 nGyh −1 (0.059 μGyh −1 ). By comparison, the results of the absorbed dose rates in this study compare well with the range of dose rates values reported for other countries (UNSCEAR 2000 ) as well as results from similar studies carried out in other mines in Ghana (Darko et al 2010 ; Faanu et al 2010 , 2013 , 2014 ) although the average absorbed dose rate of 80 ± 20 nGyh −1 measured in air from the study area is above the worldwide average. The reasons for the higher values of the doses for external gamma could be due to difference in geological formations as well as contribution from cosmogenic radionuclides in addition to terrestrial radionuclides as observably in Fig.…”

“…For 232 Th, the average activity concentration is 71.8 ± 2.2 Bqkg −1 in range of 35.0–116.7 Bqkg −1 and that of 40 K is 1168.3 ± 15.8 Bqkg −1 in a range of 500.0–1795.9 Bqkg −1 . The results of this study also compare with the previous study that was carried in Perseus Mining (Ghana) Ltd., (Fannu et al 2013 , 2014 ). As shown in Table 3 , the average values of the activity concentrations of 238 U and 232 Th in this study are about two times higher than the world average whilst that of 40 K is about three times higher than values in normal continental soils (UNSCEAR 2000 ).…”

“…Perseus Mining (Ghana) Ltd., is one of the several mining companies in Ghana located at Ayanfuri, of Ghana. Earlier study by Faanu et al ( 2013 , 2014 ), on part of the mine’s concession gave an average activity concentrations for 238 U, 232 Th and 40 K as 64.3, 68.4 and 1243.9 Bqkg −1 respectively. This study became necessary as a result of operational expansion to another part of the concession, hence, the need to carried baseline radioactivity survey in order to establish the levels of radioactivity in the area before commencement.…”

Radioactivity of Soil, Rock and Water in a Shale Gas Exploitation Area, SW China

“…However, the activity concentrations of 226 Ra in the shale in this study are within the results of northern PA in the USA [35]. The difference in radioactivity levels in different areas can be attributed to differences in the local geological and geochemical conditions, especially for soil, and the specific levels are closely related to the type of parent rock [36,37]. By comparison (Table 4), all of the activity concentrations of gross-α and gross-β in the soil in this study compare well with the results of similar studies reported in the Kinta and Segamat Districts, Malaysia [27,28] and Chihuahua City, Mexico [29].…”

“…However, the activity concentrations of 226 Ra in the shale in this study are within the results of northern PA in the USA [35]. The difference in radioactivity levels in different areas can be attributed to differences in the local geological and geochemical conditions, especially for soil, and the specific levels are closely related to the type of parent rock [36,37]. …”