Monitoring pesticides residues in water resources of the Lake Naivasha catchment using passive sampling

Passive samplersare able to recoverthe detectionof low concentrations usingcontinuous gatheringthe pollutants.While these contaminants might beundetected withtheconventional grab samplingwhich is anonce-off time-point sampling.In this study,Silicone rubber sheet samplers were used as the passive sampler to monitor the residue of some organochlorine pesticides, notably; α-HCH, β-HCH, γ-HCH, δ-HCH, Heptachlor, Aldrin, Heptachlor Epoxide, pp-DDE, Endrin, Dieldrin, α-endosulfan, β-endosulfan, pp-DDD, Endrin aldehyde, pp-DDT, Endosulfan Sulphate and Methoxychlor in the Lake Naivasha basin, Kenya.The samplers were deployed in the water for one month after which the concentration of the pesticides was measured by analyzing the extraction of samplers using the GC-ECD. Determiningthe organochlorine pesticidesresidues by means ofthe Silicone rubbersamplers demonstrated thatthe maximumcontamination occurredat the lake sitewith the total sum concentration of 81ng/L which is the final accumulation location for surficial hydrological,chemical and sediment transport through the river basin. The total organochlorine residue changed to 71.5ng/L for the Middle Malewa and 59ng/L for the Upper Malewa river sampling sites.Finally, comparing the concentration of the studied pesticides with the maximum standard limit showed that the concentrations were below the limit. However, because of the risk of these pesticides continued monitoring of pesticides residues in the catchment remains highly recommended.