Determination of organochlorine pesticides in the agricultural soil of Oke-Osun farm settlement, Osogbo, Nigeria

Abstract

This study was conducted to evaluate the levels and seasonal variations of some organochlorine pesticides (OCPs) in the cultivated land of Oke-Osun farm settlement, Osogbo, Nigeria. A field sampling programme was conducted in the rainy and dry seasons for 4 months each resulting in the analysis of a total of 40 samples. Soil samples collected at 20-m intervals were air-dried to a constant weight, sieved through a mesh of 2.0-mm pore size and selected by coning and quartering method. Solid-liquid extraction was used to extract OCPs from the soil. Qualitative identifications and quantitative evaluation of the OCPs were carried out with the aid of a Perkin Elmer gas chromatograph coupled with electron capture detector. Seasonal mean ranges of OCPs in soil (μg/kg) were 13.09 ± 21.66 β-BHC-42.01 ± 17.50 p, p(')-DDT in rainy season and 30.74 ± 17.38 α-BHC-82.88 ± 32.24 p, p(')-DDT in the dry season. The results obtained from this study revealed that agricultural soil samples of Oke-Osun farm settlement were contaminated with persistent organochlorine pesticides mainly as a result of their applications by farmers. Higher levels of OCPs were obtained for dry season than the rainy season. There were indications from this study that pesticides that have deleterious health effects on humans previously placed under legal restrictions by regulatory agencies were still being used by the farmers of Oke-Osun farm settlement and this gives cause for environmental concern.