LEVELS OF ORGANOCHLORINE PESTICIDE RESIDUES IN SOIL, WATER AND SEDIMENT FROM SOME SELECTED COCOA FARMS IN ONDO STATE, NIGERIA

Abstract

This research project investigated the level of Organo-Chlorine Pesticides (OCPs) residues in in cocoa farms from three major cocoa-producing Local Government Areas including Akure-South, Ifedore, and Idanre, in Ondo State Central Senatorial District. Soil, stream water, and sediment samples from selected cocoa farms in the areas were sampled and analysed with the modern Shimadzu GC-MS QP-2010, following extraction with organic solvent mixtures and clean-up in silica micro-column. Endosulfan I occurred most frequently in the samples and at very high concentrations of 350.10 mg/kg in the soil samples, 6.49 mg/L in water and 127.14 mg/kg in the sediment. Endosulfan II was also detected in most of the samples but at much lower concentrations compared to endosulfan I. The three isomers of Benzene hexachloride: α-BHC, β-BHC, and δ-BHC were detected in some samples from Akure-South and Ifedore areas, and their concentrations were found to be associated with the application of the Ƴ-isomer (lindane); which occurred at concentration of 0.037mg/L in the water sample from Akure South, and this is above the WHO guideline limit of 0.002 mg/L for lindane in water. Lindane was also found in all the sediment samples from Ifedore area, with a mean concentration of 2.1335 mg/kg. Varied concentrations of heptachlor, heptachlor epoxide, aldrin and dieldrin were also measured in the various samples. The sum total concentration of the Organochlorine Pesticides (mg/kg) in the soil samples was found to show a positive correlation with the total organic matter contents of the soil, with high correlation coefficients (> 90%) in all the areas. The research thus, provides information on the current and health risk residue levels of organochlorine pesticides in soil, water and sediment of the study areas with which future environmental performance on the use of pesticides on cocoa farms could be progressively monitored.