Study of soil-fern transfer of naturally occurring alpha emitting radionuclides in the Southern Region of Cameroon

Publication date: December 2017
Source:Journal of Environmental Radioactivity, Volume 180
Author(s): S. Mvondo, G.H. Ben-Bolie, J.M. Ema'a Ema'a, P. Owono Ateba, P. Ele abiama, J.F. Beyala Ateba
This study was carried out in the localities Melondo and Ngombas located in the Southern Region of Cameroon where there are known to be uranium-bearing and high background radiation areas. Activity concentrations of naturally occurring radionuclides ²¹⁰Po, ²³⁸U, ²³⁵U, ²³⁴U, ²³²Th, ²³⁰Th, ²²⁸Th and ²²⁶Ra were determined in soil and fern (filicophyta) samples collected at 10 points in both localities. In soil, the average values of these activity concentrations (in Bq.kg⁻¹ d.w.) were ²¹⁰Po(130 ± 10), ²³⁸U(126 ± 11.6), ²³⁵U(5 ± 1), ^234U(131 ± 10), ²³²Th(400 ± 22), ²³⁰Th(145 ± 11), ²²⁸Th(381 ± 21) and ²²⁶Ra(154 ± 28) at Melondo; and ²¹⁰Po(228 ± 1), ²³⁸U(170 ± 11), ²³⁵U(9 ± 2), ²³⁴U(179 ± 12), ²³²Th(200 ± 18), ²³⁰Th(184 ± 18), ²²⁸Th(228 ± 22) and ²²⁶Ra(416 ± 7) at Ngomba. In fern the average activity concentrations were: ²¹⁰Po(35 ± 3), ²³⁸U(0.68 ± 0.05), ²³⁵U(0.042 ± 0.01), ²³⁴U(0.90 ± 0.05), ²³²Th(1.2 ± 0.2), ²³⁰Th(0.7 ± 0.1), ²²⁸Th(39 ± 3) and ²²⁶Ra(14 ± 3) at Melondo and ²¹⁰Po(24 ± 2), ²³⁸U(0.82 ± 0.06), ²³⁵U(0.046 ± 0.01), ²³⁴U(0.92 ± 0.06), ²³²Th(0.8 ± 0.2), ²³⁰Th(0.9 ± 0.2), ²²⁸Th(15 ± 5) and ²²⁶Ra(14 ± 3) at Ngomba. The soil-fern transfer factors (TF) (in kg.kg⁻¹) were respectively ²¹⁰Po(1.64 × 10⁻¹), ²³⁸U (5 × 10⁻³), ²³⁵U(7 × 10⁻³), ²³⁴U(6 × 10⁻³), ²³²Th(3 × 10⁻³), ²³⁰Th(5 × 10⁻³), ²²⁸Th(7.9 × 10⁻²), and ²²⁶Ra(5.1 × 10⁻²). The highest TF for fern was for ²¹⁰Po, probably because of atmospheric deposition. The TFs of uranium and thorium were comparable to those given in the IAEA handbook for grass.



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