Pesticide contamination in Lake Naivasha (Kenya)

Water, sediment, red swamp crayfish (Procambarus clarkii) and blackbass (Micropterus salmoides) From Lake Naivasha were analyzed for selected organochlorine and organophosphorus pesticide residues. The mean p,p´-DDT, o,p´-DDT and p,p´-DDE residue levels recorded in blackbass [28.3 ppb ((30.0 ppb SD), 34.2 (54.0) and 16.1 (16.1) ppb, respectively] and crayfish [4.6 (5.1), 3.2 (2.8), and 1.4 (1.1) ppb, respectively], were higher than recorded in previous works. This indicated recent usage of technical DDT in the lake´s catchment. Levels of p,p´-DDT higher than those of p,p´-DDE further emphasized this. Mean lindane, dieldrin, (-endosulfan and aldrin concentrations in blackbass were 100.5, 34.6, 21.6 and 16.7 ppb, respectively. The same residues were detected at lower concentrations in crayfish (2.0, 2.0, 2.0 and 1.9 ppb, respectively). The higher fat content 3.7 (2.7% SD) in blackbass (compared to 0.6 (0.3% in crayfish) accounted for the significantly higher residue concentrations in blackbass. Organophosphate pesticides were the most commonly used pesticides in the lake´s catchment, but none was detected in any of the samples