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Water samples from boreholes collected from 29 locations in two local government areas in Port Harcourt, Rivers State, Nigeria have been analysed for their natural radioactivity content using a well-calibrated, shielded and highly efficient NaI(Tl) detector based gamma ray with a view to provide baseline data on the radioactivity level in the area, as well as an estimate of the resulting dose on the inhabitants. The radionuclides observed with reliable regularity belonged to the decay series chain headed by (238)U and (232)Th as well as the non-series (40)K. The mean specific activity concentrations of these, are 3.51 +/- 1.22, 2.04 +/- 0.29 and 23.03 +/- 4.37 Bq l(-1), respectively. The respective corresponding estimated mean annual effective dose are 0.36 +/- 0.12, 0.51 +/- 0.07 and 0.05 +/- 0.01, respectively mSv y(-1). These results are relatively high but are still below the recommended limit of 1 mSv y(-1) due to borehole water only. This study is the first in the area and can usefully be associated with similar surveys in other matrices in the area. Meanwhile, the radionuclides detected in the water samples do not seem to pose any radiological consequence on the sample population.
Avwiri et al. (Thu,) studied this question.