Concentration of Organophosphorous Pesticide Residues in Water and Sediment Samples from River Ilaje, Nigeria

The levels of organophosphorous pesticide residues were determined form water and sediment samples collected from two sampling point within river Ilaje during the dry and rainy seasons. The extracts were analyzed for the presence of organophosphorous pesticide residues using a Gas chromatography coupled with Mass Spectrometer (GC-MS) to identify and quantify the various organophosphorous pesticide residues. The result shows that all the samples analyzed were contaminated with some levels of organophosphorous pesticide residues. The pesticides detected include Diazinon, Phosphamidon, Dichlofenthion, Methyl Parathion, Pirimiphos-methyl, Parathion, Bromophos-ethyl, Ethion, Carbofenothion, Carbaryl and Fenthion. The mean concentration of the pesticide residue in water samples ranges from not detected to 7.087 mg/l (Phosphamidon) during the dry season and from not detected to 4.456 mg/l (Ethion) during the rainy season. For the sediment samples the mean concentration ranges from not detected to 2.256 µg/g (Phosphamidon) during the dry season and from not detected to 1.717 µg/g (Phosphamidon) during the rainy season. This shows that in the water samples, the concentration of Phosphamidon was highest during the dry season while the concentration of Ethion was highest during the rainy season. The concentration of Phosphamidon was the highest in the sediment samples for both seasons.