Occurrence of natural radionuclides and fallout cesium-137 in dry-season agricultural land of South Western Nigeria

The radioactivity of the Opa river - irrigated farmlands in the south weste rn Nigeria was determined using an HpGe based, low-level passive gamma-coun ting system. With the exception of two isotopes, the main radionuclides ana lysed in the sample were the progenies of U-238 and Th-232. The other two i sotopes were the naturally occurring K-40 and the anthropogenic Cs-137. Th, result obtained showed elevated levels of radioactivity from all detected radionuclides compared to the published data for this area. Enhanced levels of naturally occurring radionuclides is attributed to the use of phosphati c fertilizers for dry season vegetable cultivation along this river banks. The presence of the fission product Cs-137 could be traced to the fallouts occasioned by the various French nuclear tests in the Sahara desert, and pr obably, some effect of the more recent nuclear reactor accident at Chernoby l in 1986.