Organochlorine and organophosphorous pesticide residues in the Oueme River catchment in the Republic of Benin

The Oueme River is one of the most important rivers in the Republic of Benin. It is 5 10 km long and its catchment drains 75% of the country. In this study, organochlorine and organophosphorous pesticide residues were measured in more than 35 sediment samples collected on nine locations along the Oueme River from upstream to downstream. Except for one location, Taneka-Koko, all areas were contaminated by more than 20 pesticides. Organochlorine pesticides identified in sediment samples included pp'-DDE, op'-DDD, pp'-DDD, op'-DDT, pp'-DDT, alpha-endosulfan, -endosulfan, beta-endosulfan sulphate, alpha-HCH, beta-HCH, lindane, aldrin, dieldrin, endrin, telodrin, isodrin, cis- and trans-heptachlorepoxide, hexachlorbutadiene, hexachlorobenzene and octachlorostyrene. The organophosphorous pesticide chlorpyrifos, used in a new formulation to protect cotton, was also identified. In some areas, the concentrations of organochlorine pesticides in the sediment of the Oueme River exceeded environmental quality standards and are reason for concern. (c) 2006 Elsevier Ltd. All rights reserved.