Analysis of naturally occurring radioactive material and radiocesium in Sediments from the Wonderfontein Catchment Area in the North-West Province and Mosses from Minsk (Belarus) using gamma spectrometry and gas-flow proportional counting

Abstract

The mining and mineral processing activities around the Wonderfonteinspruit catchment area have been responsible for the discharge of waste into the stream for many years, causing the accumulation of radioactive nuclides in sediments. Afar a field , the Chernobyl nuclear power plant accident and other activities such as atmospheric nuclear explosions caused a huge distribution of fallout radioactive products into the environment especially from Minsk area in Belarus. A large number of sediment samples collected in the catchment area and several mosses samples from the Minsk area were measured using high resolution gamma spectrometry for gamma measurements and gas-flow proportional counter for gross alpha-beta counting. Interference by other nuclides due to comparable photopeaks of interval has been corrected for. All the natural decay chains have been assayed. The average 238U determined from the 234Th has been found to average 0.934 ± 0.014 Bq/g with median at 0.621 Bq/g. This is twice the legislated exemption level of 0.5 Bq/g. The average activity concentration for the 235U (0.040 ± 0.004 Bq/g) is within the legislated exemption level. The average concentration for 232Th of 75.4 mBq/g is well below the legislated exemption level. Radioactivity equilibrium between parent and daughter nuclides has been observed taking into account the 150 years sedimentation since the start of mining activities. No deposits of 134Cs and 137 Cs have been observed in the catchment area but the activity concentrations of these nuclides are still detectable in the mosses from the Minsk (Belarus). The gross alpha-beta activities are well correlated with the gamma spectrometric results. The potential radiological hazard to human has been projected taking into account all the sources of radioactivity. This may be through direct drinking of water from the catchment area by the communities living around it.