A study was conducted over three different seasons in which organochlorine pesticides (OCP) residue water and sediment samples were collected from 14 purposefully selected riverine and earthen fish pond representative sites within Lake Victoria Basin, Kenya, catchment. Extrusion liquids were analyzed for contamination levels using gas chromatograph (equipped with an auto sampler and an electron capture detector (ECD) and confirmed using GC/MS. Main aim was to find out if locally banned or restricted pesticides still find their way into our environment, hence implication on the fragile aquatic ecosystem and human health. Mean concentrations of DDTs, cyclodienes and HCHs in earthen fish ponds’ waters were in undetectable to 0.27±0.03mgL-1, undetectable to 0.11±0.00mgL-1, and 4.39±1.01mgL-1 levels respectively; and those in receiving waters were undetectable to 0.23±0.01mgL-1, 1.20±0.005mg L-1, and 1.71±0.02mgL-1 respectively. Further, mean contamination by OCPs in sediment samples were noted to be significantly (p<0.05) higher in dieldrin (11.043±0.43mgkg-1), endrin (4.16±0.460mgkg-1), Heptachlor (1.61±0.02mgkg-1) DDT (128.97±1.32mgkg-1), endosulphan (12.27±1.051mgkg-1), methoxychlor (37.51± 1.641mgkg-1) and lindane (8.96±1.32mgkg-1), respectively. An obvious spatial distribution pattern was noted both in water and sediment readings over the sampling period. This demonstrates that cyclodienes are the predominant contaminants and some non-point sources in water courses. Taking p< 0.05 as the alpha level, it was observed that there was a statistical significant difference in the residue levels between seasons. The pollution levels in study sites were compared with other studies, suggesting the extraction and analysis method is suitable for long-term on-line monitoring of trace OCPs in aquatic ecosystems. Therefore, continuous studies monitoring OCPs in upstream catchment areas is essential to further understand the future trend of contamination for appropriate policy and management.
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Keywords: organochlorine pesticides, Lake Victoria Basin, residues, EC-GCD, human health