Determination of organochlorine pesticide residue in sediment and water from the Densu river basin, Ghana

► OCPs in sediment and water sampled from the Densu river were determined to evaluate the status of contamination. ► Significant difference was observed among the samples collected from three locations along the river. ► Sediment samples recorded exceedingly higher concentrations of the pesticides compared to the water samples. ► Some of the organochlorine pesticides were above permissible limits set by WHO and Australia. ► Continuous monitoring program is recommended in view of the significant role the river plays in water supply purposes in Accra. The distribution of organochlorine pesticides in the aquatic ecosystem from the Densu river revealed varying levels of concentration in water and the sediment samples. Three locations were sampled along the river to evaluate the levels of organochlorine pesticide residue in the river. Sediment and surface water samples were extracted by soxhlet and liquid–liquid extraction respectively and analyzed using Gas Chromatograph coupled with electron capture detector. The detectable organochlorine pesticides were gamma-hexachlorocyclohexane (HCH), delta-hexachlorocyclohexane, heptachlor, aldrin and dieldrin. The other pesticides that were investigated are gamma-chlordane, alpha endosulfan, endosulfan sulfate, p,p′-DDT and its metabolite p,p′-DDE, methoxychlor, endrin and its metabolite endrin aldehyde and endrin ketone. The order of increasing frequency of detection of samples was higher in sediment than water. In sediment, the mean concentration ranged from 0.030 μg kg −1 dry weight (endrin) to 10.98 μg kg −1 dry weight (aldrin). The highest detected concentration of organochlorine in water was endosulfan sulfate with mean concentration of 0.185 μg L −1. Analysis of variance indicated significant differences for most organochlorine pesticide residue in the sediment sampled from the various locations. Some of the levels of organochlorine pesticides detected in water were relatively high compared to guideline values set by World Health Organization and Australia and thus could be harmful if the trend is not checked.