Abstract:
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.
