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.

No abstract

No abstract

Rainfall is undoubtedly a determining agro-meteorological factor in the cultivation and production of cocoa. This work has revealed that rainfall has a constraining ability on cocoa yield in the core cocoa production areas of Ondo state, Nigeria. It was also established that cocoa production is in its best in areas like: Idanre, Ondo, Akure, Ile-Oluji, Owo e.t.c, which have yields above 1000MT per annum and rainfall lesser than 51.30mm. Cocoa yield was also shown to be the inverse of annual rainfall level. This was evident as cocoa yield increased in the early and latter months of the year when the rains are yet to fully come, and suffered in the mid year at the heart of raining season. A model of rainfall as it affected cocoa yields was achieved in this work.

Radon gas is by far the most important source of ionizing radiation among those that are of natural origin. In this study, radon was measured in some homes built of different types of building materials in Akoko region of Ondo state, Nigeria. The test was conducted using Accustar alpha track long term passive test devices containing CR-39 solid state nuclear track detector foil. The detectors were exposed for a period of six months. After removal the detectors were subsequently etched electrochemically and counted with computer aided image analysis system. The results show that radon concentration varies between 15.00 Bqm-3 to 141.00 Bqm-3 with a mean of 35.54 Bqm-3 and geometric mean of 29.95 Bqm-3. Annual exposure varied between 0.10 WLM to 0.17 WLM with a mean of 0.13 WLM, annual effective dose varied between 0.38 mSvy-1 to 0.69 mSvy-1 with a mean of 0.50 mSvy-1 and lifetime fatality risk varied between 0.50x10-4 to 0.85x10-4 with a mean of 0.64x10-4 in bedroom, living room, store and lobby. This study shows that the local soil origin greatly contributes to radon concentrations recorded in these areas.