Concentration and vertical distribution of 137Cs in the undisturbed soil of southwestern Nigeria.

摘要

The results of measurements of 137Cs in soil profiles that were sampled in undisturbed soil in Ondo, Ekiti, and Oyo states in the southwestern area of Nigeria are presented in this paper. Samples were collected from nine soil profiles. The vertical distributions of 137Cs in the soil profiles have been determined. Cesium concentration ranged from 0.31 +/- 0.10 Bq kg(-1) in the 0-2 cm depth to a maximum of 1.25 +/- 0.21 Bq kg(-1) in the 6-8 cm depth at some sites and from 3.16 +/- 0.16 Bq kg(-1) in 0-5 cm depth to below detection limit (BDL) at 20-25 cm at another site. 137Cs total deposition in 0-10 cm depth was found to be greatest at Ikogosi site with a value of 90.30 Bq m(-2). The results generally showed that more than 40 y after the first nuclear weapon tests, 137Cs still remains within the 25 cm upper layer of soil in the region with a migration velocity of 0.17-0.18 cm y(-1). The mean value of effective dose commitment due to the presence of cesium in soil in the entire region was found to be 10.77 microSv.