Abstract

The levels of organochlorine pesticide residues in water and fish from some rivers in Edo State were determined. The water samples were extracted with 15% diethyl ether in hexane, the extracts were treated with copper tunings for the elimination of sulphur interference and analyzed using a gas chromatograph fitted with an electron capture detector. In all the water samples analyzed, the organochlorine pesticide residues determined (Lindane, Aldrin, pp-DDE, op-DDD, pp-DDD, op-DDT, and pp-DDT) were present, except in Ikoro River, where the water samples exhibited non-detectable levels of pp-DDE and pp-DDT.  The level of pp-DDT, (0.7442 ppb) was highest in Ogba River, followed by Lindane (0.7130 ppb), Aldrin (0.5985ppb). Lindane (0.7928 and 0.5912ppb) was found to be highest in river Ovia and Ikoro respectively followed by Aldrin (0.7731 and 0.4867 ppb). The other organochlorine pesticides were present in varied levels from 0.3097 - 0.4860 ppb in Ogba River; ND-0.3100 ppb in Ikoro River and 0.3019 - 0.5557 ppb in Ovia River. The pesticides residues in fish samples were extracted by Soxhlet extraction process using a mixture of hexane and acetone, the extracts cleaned and analyzed using a gas chromatograph fitted with an electron capture detector. The organochlorine pesticide residues detected in water were also present in the fishes but at higher concentrations. This can be due to OCPs being lipophilic. The concentrations of these OCP residues were more in the bottom to middle feeders (Cts) than in the top to middle feeders (Tzs). Lindane levels (0.063 mg/g); 0.054 and 0.039 mg/g were detected in fish from Ovia, Ogba and Ikoro rivers respectively. While Aldrin was found present in 0.059 and 0.027 mg/g in the bottom and top feeders from Ovia river. However these levels were quite high when compared with the allowable Federal Environmental Protection Agency (FEPA) now Federal Ministry of Environment limits and can be harmful if the trend is not checked.  

Key words: Organochlorine, pesticide residues, rivers, fishes, safety, water, seafood.