Özet:

Total reliance on quarry products as construction materials has prompted commercial quarry activities globally. However, potential risks introduced by radiation exposure to quarries in two different locations in Ondo State, Nigeria were assessed to evaluate the background radiation and distribution of naturally occurring radionuclides associated with these areas. A ground radiometric mapping of eleven traverses across the two quarry sites was carried out using Gamma ray spectrometer. Naturally occurring radionuclides 238U, 232Th and 40K in natural quarried materials of coarse rock aggregates and soil samples collected at a maximum depth of 2 m and up to 500 m away from the quarry sites were measured using gamma spectrometry method. Spectrometric data were processed and presented in form of radiometric maps showing the distribution of radiation level in each location. Results show that activity concentrations varied from one location to another. The radiation level in the recently quarried coarse rock aggregates (QF1 and QF2) (372 cps and 382 cps) are higher than the previously quarried coarse rock aggregates (QP1 and QP2) (365 cps and 377 cps) of the quarry sites. Activity concentrations in soils are in the order 232Th < 238U < 40K. The mean radioactivity concentration values of 232Th, 238U and 40K are 0.0027±0.0003 Bq/kg, 0.028±0.0012 Bq/kg, 47.45±0.0313 Bq/kg and 0.0036±0.00036 Bq/kg, 0.026±0.0012 Bq/kg and 69.42±0.0313 Bq/kg respectively for soils within the quarries. At 500 m away from the quarry sites, mean values are 0.0008±0.75 Bq/kg, 0.020±0.0012 Bq/kg, 41.54±0.0313 Bq/kg and 0.0049±0.0004 Bq/kg, 0.052±0.0012 Bq/kg and 200.32±0.0313 Bq/kg respectively. The radiological hazard indices calculated were used to access the health implication of exposure to rock aggregates and soil of the study areas. The values obtained when compared with their corresponding world permissible values were found to be below the internationally recommended values. Therefore, the level of radiation and interaction with the rock aggregates and soils do not expose the workers and people within and around the quarries to health problem. Hence, the quarry products can be used as building material for housing and road constructions.

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