Organochlorine pesticide residues in water and sediments in river Kibos-Nyamasaria in Kisumu County: An inlet river of Lake Victoria, Kenya

The misuse of organochlorine pesticides (OCPs) and the lack of adequate regulations have led to contamination of rivers and lakes. In this study, we determined the concentrations of OCPs that have either been banned or restricted for use in the Kibos-Nyamasaria River during two seasons: wet (April-May) and dry (February-March). OCPs were analyzed using GC-MS. Nineteen pesticide residues were detected in the river (water) and sediments. In water, aldrin had the highest concentration of 8.33±0.58 μg/L, dieldrin (8.67±0.5 μg/L), endosulfan sulphate (0.23±0.00 μg/L), α-endosulfan (0.19±0.00 μg/L), methoxychlor (4.57±0.03 μg/L) and α-HCH (3.47±0.00 μg/L) during the wet season, while dieldrin (6.03±5.1 μg/L), methoxychlor (3.43±0.06 μg/L), and α-HCH (8.27±0.06 μg/L) were above 0.1 μg/L detection limit during the dry season. In sediments, aldrin, methoxychlor, and δ-HCH were not detected in either season; however, dieldrin and β-endosulfan were detected only during the dry season. Additionally, OCPs were above 0.2 μg/kg (maximum residue level (MRLs). The concentration of OCPs increased downstream as the river approached Lake Victoria. Because some pesticides were present at levels beyond the recommended limits, strategies must be developed to reduce them and identify potential sources of banned pesticides.