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

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 radionuclides210 Po,238 U,235 U,234 U,232 Th,230 Th,228 Th and226 Ra 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.) were210 Po(130 ± 10),238 U(126 ± 11.6),235 U(5 ± 1),234U (131 ± 10),232 Th(400 ± 22),230 Th(145 ± 11),228 Th(381 ± 21) and226 Ra(154 ± 28) at Melondo; and210 Po(228 ± 1),238 U(170 ± 11),235 U(9 ± 2),234 U(179 ± 12),232 Th(200 ± 18),230 Th(184 ± 18),228 Th(228 ± 22) and226 Ra(416 ± 7) at Ngomba. In fern the average activity concentrations were:210 Po(35 ± 3),238 U(0.68 ± 0.05),235 U(0.042 ± 0.01),234 U(0.90 ± 0.05),232 Th(1.2 ± 0.2),230 Th(0.7 ± 0.1),228 Th(39 ± 3) and226 Ra(14 ± 3) at Melondo and210 Po(24 ± 2),238 U(0.82 ± 0.06),235 U(0.046 ± 0.01),234 U(0.92 ± 0.06),232 Th(0.8 ± 0.2),230 Th(0.9 ± 0.2),228 Th(15 ± 5) and226 Ra(14 ± 3) at Ngomba. The soil-fern transfer factors (TF) (in kg.kg-1 ) were respectively210 Po(1.64 × 10-1 ),238 U (5 × 10-3 ),235 U(7 × 10-3 ),234 U(6 × 10-3 ),232 Th(3 × 10-3 ),230 Th(5 × 10-3 ),228 Th(7.9 × 10-2 ), and226 Ra(5.1 × 10-2 ). The highest TF for fern was for210 Po, probably because of atmospheric deposition. The TFs of uranium and thorium were comparable to those given in the IAEA handbook for grass.