Abstract

This study set out to survey pesticide usage and concentrations of their residues in lowerYala/Nzoia catchment areas of Lake Victoria, Kenya during the dry and rainy seasons of 2009. Water and sediment samples were analyzed for selected organochlorine and organophosphorus pesticide residues using gas chromatography equipped with electron capture detector. The findings of the survey showed that the banned organochlorines are still being used in the catchment. Pesticide residue levels of organochlorines in water samples from Yala/Nzoia Basin were below detection limit (BDL) both during the rainy and dry seasons. The residue levels detected in sediment samples collected during the rainy season ranged from 0.05 to 59.01 µgkg^-1, whereas during the dry season, they ranged from BDL-24.54 µgkg^-1. The concentrations of dieldrin and p,p’-DDD were notably higher (p < 0.05) than aldrin and p,p’DDT, respectively, in most of the samples. No organophosphates were detected in any of the water and sediment samples. Organochlorine residues detected in sediment in both seasons were below the World Health Organization recommended guidelines. Therefore, it was concluded that there were neither environmental nor human health hazards posed by these compounds in the water and sediments.

Key words: Organochlorine, organophosphorus, residues, Lake Victoria