O. K. Adukpo

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

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.

Reply to the letter written by Mayeen Uddin Khandaker on: “Distribution and assessment of radionuclides in sediments, soil and water from the lower basin of river Pra in the Central and Western Regions of Ghana” (DOI 10.1007/s10967-014-3637-5)

1. He thought the minimum detectable activity (MDA) value for K is too low, the counting time was too short based on his experience and why distilled water was used. First of all the distilled water was used to limit the level of backscatter radiation within the detector system during the background count. Also, we want to state that a low background spectrometry system was used for the counting. In other to optimize the result of the background count and the real samples, the same counting time was used. We agree that the longer the counting time the greater the peak area, however, based on the prevailing laboratory condition which could not enable us to consider a longer counting time 36,000 was used which could also give an appreciable count rate. The MDA is defined as the smallest quantity of radioactivity that could be measured under specified conditions, and is another factor which is an important concept in environmental level measurement. The MDA depends on the lower limit of detection (LLD) and the counting efficiency of a counting system. The MDA is very important, particularly in environmental level systems, where the count rate of a sample is almost the same as the count rate of the background. The MDA was calculated using the conventional MDA method based on statistical convergence of 95 % confidence level. The value obtained for K was based on experimental data and calculation done using the conventional method.

Radiological impact of soil as a source of building material

The radiological hazards associated with naturally occurring radioactive materials in soil samples from different geological locations have been studied using gamma spectrometry. The average activity concentration of 226 Ra, 232 Th, and 40 K were (16.4-74.6 Bq/kg), (12.0-44.7 Bq/kg), and (215.4-498.6 Bq/kg). The highest values of 226 Ra and 232 Th occurred in Dodowa and Oyibi respectively. The 40 K recorded the highest activity concentration of 498.6 Bq/kg, measured in soil from McCarthy Hills. The radium equivalent activity (Ra eq ; 46.9-135.7 Bq/kg), the internal hazards index (H in ; 0.29-0.52) the external hazard index (H ex ; 0.22-0.37), the absorbed dose rate in air (23.3-75.8 nGy/h), and the annual effective dose (E T ) (44.4-79.4 uSv/y) were evaluated to assess the radiation hazard to the populace living in dwellings made of these soil as a building material. The results obtained were found to be within the acceptable limits for public exposure control recommended by the European Commission, International Commission on Radiological Protection, and Organization for Economic Cooperation and Development-Nuclear Energy Agency.

Impact assessment of naturally occurring radioactive materials on the public from gold mining and processing at Newmont Golden Ridge Limited, Akyem, Eastern Region of Ghana

Baseline radioactivity levels of naturally occurring radioactive materials within the operational area and surrounding communities of Akyem Gold Mine of Newmont Golden Ridge Limited of Ghana were determined based on direct gamma-ray spectrometry to quantify the radionuclides of interest, namely,238 U,232 Th, and 40 K in soil samples. The average activity concentrations of 238 U,232 Th, and 40 K in the soil samples were 11.90, 11.39, and 139.71 Bq/kg, respectively. For the water samples, the concentration values of gross-alpha and gross-beta for all the water samples were below the Ghana Standards Board (now Ghana Standards Authority) and World Health Organization recommended guideline values for drinking water quality. The annual average effective dose to the public due to gamma ray exposures from the soil samples was estimated to be 0.03 mSv which is below the UNSCEAR 2000 average reference level of 0.07 mSv for public exposure control. The results obtained in this study also show that radiation levels are within the natural background radiation levels found in literature and compare well with the results of similar studies in Ghana.

Measurement of radon activity in soil samples of some selected towns across the Lake Bosumtwi basin, Ghana

Background: The potential hazard of radiation exposures to radon and its daughter products from natural background has been highlighted in the world of scientific press and has become a matter of concern. The Lake Bosumtwi is one of the interesting research areas in Ghana due to the geological nature of the area, and also of its great importance based on the different uses of the lake and its surroundings. There is therefore the need to investigate the levels of radon activity in soil samples around Lake Bosomtwi basin as part of the national effort to establish base line data of radon levels in Ghana. Materials and Methods: The study was conducted to measure the levels of radon activity in soil samples within the lake Bosomtwi basin. Samples were collected from five selected villages around the lake at depths of 10 cm and 20 cm. The Roles Method was employed and measurements were made using specific cell counters. The measurements were performed with a Radon Degassing Unit (RDU-200) and a Radon Detector Analyzer (RDA-200). The calculated cell efficiency was obtained as 0.55 cpm/dpm. Results: The average radon concentrations at the depths were calculated and the maximum concentration for the 10 cm depth was obtained from Tepaso with a value of 4801.71±678 Bq/m 3 and the minimum concentration was obtained from Abonu with a value of 3887.07±815 Bq/m 3 . The maximum and minimum concentrations for the 20 cm depth were obtained from Tepaso and Kusuasi with values of 5602.10±943 Bq/m 3 and 4877.93±404 Bq/m 3 respectively. The overall average radon concentration obtained was 4745.31±559 Bq/m 3 . The results obtained were high when compared with results from previous studies. The values obtained are less than the World Health Organizations acceptable level for outdoor radon activity which is quoted as 9250 Bq/m 3 and hence the public are not exposed to any significant radiological health hazard in these areas. Conclusions: The radon concentration at the depth of 20 cm was found to be higher than the 10 cm depth and this shows that radon gas in soil increases with depth. The values obtained are less than the World Health Organizations acceptable level for outdoor radon activity and life activities would not be at risk in these areas.