Abstract

Tin mining in the Jos Plateau, Nigeria has left the residents with a legacy of radioactively contaminated soils, polluted water supplies, scattered heaps of radioactive mine/mill residues and radioactive mine ponds/steams. The gamma radiation of sediment samples collected from the tin mine streams at Kokop, Zawan, Sabon Barki and Yelwa, which the residents used in building constructions, were measured. The samples were collected, dried under ambient temperature and sealed in plastic containers and the activity concentrations of $^{40}K, \>^{226}Ra$ and $^{232}Th$ measured in the laboratory using NaI (Tl) gamma-ray spectrometry technique with an accumulating time of 30,000seconds per sample. Similarly, elemental concentration levels of the samples were determined using XRF technique. The Kokop, Zawan, Sabon Barki and Yelwa measured range of activity concentration levels for $^{40}K, \>^{226}Ra$ and $^{232}Th$ were (324-955) Bq/kg, (307-461) Bq/kg and (851-1203) Bq/kg; (154-267) Bq/kg, (89-157) Bq/kg and (78-111) Bq/kg; (163-322) Bq/kg, (77-108) Bq/kg and (115-208) Bq/kg and (134-379) Bq/kg, (61-109) Bq/kg and (156-198) Bq/kg, respectively. The radiation hazards associated with these natural building materials were assessed using three radiological models, namely; “Radium Equivalent”, “Mean Annual Effective Dose” and “Gamma Activity Concentration Index”. In each case, there was an indication that Kokop sediment samples were not safe for use in the construction of residential houses and hence poses a significant source of radiation hazards to occupants of such buildings. The Kokop’s mean recorded radium equivalent, mean annual effective dose and gamma activity concentration index were 2057.7±45.8 Bq/kg, 4.6 mSv/yr and 7.0, respectively. A total of 21 elements were detected in the sediment samples. Arsenic, the element of interest, was significantly high, much higher than the recommended acceptable level in soil to be used in construction of residential houses. This further justifies the unsafe use of the sediments in the construction of dwelling homes bearing in mind the activities of pica children who exhibit the hand- to-mouth habit and may probably be co-occupants as well.

Keywords:

Activity concentration, contaminated sediment, hazards, mill tailings,

References

Competing interests

The authors have no competing interests.

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