Assessment of radioactivity concentration levels in soil samples around some quarry sites in Akamkpa, Cross River State, Nigeria

Abstract

The presence of natural radionuclides in soil from quarry sites may present health risk potentials to the quarry workers and occupants of the quarry areas. This study is aimed to determine the activity concentration levels in soil around some quarry sites in Akamkpa, Cross River State, Nigeria. The study covers only Akamkpa, Cross River State and three quarry sites were selected at different locations. An estimation of radioactivity concentration levels in soil samples collected from the study area were carried out using Sodium Iodide (NaI) detector system at the National Institute of Radiation Protection and research, Ibadan, Nigeria thereby estimating the Absorbed Dose, Annual Effective Dose Rate, Gonadal Dose Equivalent, and Excessive Life Cancer Risk. The radioactivity concentration of ⁴⁰K, ²³²Th, and ²³⁸U at Fuaha Nigeria Limited (QMS –A) ranged from 480.00 ± 23.88 Bq/kg to 1575.09 ± 77.21 Bq/kgwith mean value of 1167.115 Bq/kg, 8.81 ± 1.10 Bq/kg to 47.83 ± 4.79 Bq/kg with mean value of 30.642 Bq/kg, and 3.96 ± 0.23 Bq/kg to 19.84 ± 1.14 Bq/kg with mean value of 12.237 Bq/kg respectively. At Xin-Xin Quarry Company (QMS-B) activity concentration ranged from 180.08 ± 9.05 Bq/kg to 1977.39 ± 96.40 Bq/kgwith mean value of 1194.113 Bq/kg, 20.36 ± 2.43 Bq/kg (B6) to 93.46 ± 8.50 Bq/kg with mean value of 49.475 Bq/kg, and 4.03 ± 0.23 Bq/kg to 17.95 ± 1.04 Bq/kg with mean value of 11.707 Bq/kg respectively. The radioactivity concentration in soil samples from the study area of Wings of Heaven Quarry Ltd. (QMS-C) were 492.29 ± 23.68 Bq/kg to 1632.49 ± 79.83 Bq/kg with mean value of 912.402 Bq/kg, 16.12 ± 1.93 Bq/kg to 48.23 ± 3.60Bq/kg with mean value of 35.965 Bq/kg, and 6.56 ± 0.37 Bq/kg to 22.32 ± 1.28 Bq/kg with mean value of 13.688 Bq/kg respectively. The absorbed doses for QMS –A, QMS-B and QMS-C were 72.830, 85.086 and 66.094nGy/hr which are respectively higher than the world average value of 50nGy/hr. The evaluated annual effective dose equivalents were 0.081mSv/y to 0.104mSv/y with a mean value of 0.091mSv/y and gonadal dose equivalents ranged from 479.125 μSv/y to 617.931 μSv/y, with a mean value of 543.141 μSv/y were found to be lower than the permissible level of 1 mSv/yr for public and 20 mSv/yr for radiation workers respectively. The estimated Excess Life Cancer Risk ranged from 0.284 x 10^-3to 0.365 x 10^-3with a mean value of 0.321x 10^-3. Residents and workers in and around Fuaha Nigeria Limited and Xin-Xin Quarry Company have higher chances of contracting cancer due to long term exposure to background radiation than those in Wings of Heaven Quarry Ltd.