Abstract

Water samples were collected from 6 different locations of the Lagos lagoon at 0.5 and 2.5 m depths, respectively and from 2 other river bodies in Lagos and analyzed for the presence of 9 OCPs (organochlorine pesticides) residues. Samples were extracted using solid phase extraction method and were analyzed with gas chromatography. The analytes quantified included chlordane (0.006 to 0.950 µg/L), heptachlor (N.D: 0.067 µg/L), methoxychlor (N.D: 0.123 µg/L), hexachlorobenzene (0.015 to 0.774 µg/L), endosulfan (0.015 to 0.996 µg/L), dichlorodiphenyltrichloroethane (0.012 to 0.910 µg/L), Dichlorodiphenyldichloroethylene (0.005 to 0.477 µg/L), dieldrin (0.015 to 0.996 µg/L) and aldrin (0.080 to 0.790 µg/L). The ratio of DDE/∑DDT obtained was 0.812 and this indicates that the degraded metabolite formed a significant proportion of the total DDTs. The overall mean total concentration of aldrin was the highest while heptachlor was the lowest. Concentration of methoxychlor and heptachlor were relatively low and below the detection limit in 50 and 57% of samples analysed respectively. The mean concentrations of organochlorine pesticides were higher than European Community allowable residual limit (0.1 µg/L) for individual OCPs in drinking water in 37.3% of samples analyzed.

Key words: Organochlorine, pesticides, Lagos, gas-chromatography, solid phase extraction.