Agricultural Practice and Pesticide Residues in Soils and Pool Sediments from the Pendjari Biosphere Reserve Area in Benin, West Africa

Abstract

One consequence of the shift in land use from traditional food production to cotton production in West Africa is the application of different pesticides. The influence of this practice on the formation of pesticide residues in soils and sediments of seasonal dry pools was investigated in 2008 and 2009 in the region of the Pendjari biosphere reserve in Benin. The protected park area, the buffer zone with some sporadic agricultural practice and the agricultural zone of the Pendjari region were compared. GC–electron capture detector method was used to analyze selected pesticides covering the officially supplied pesticides and some organochlorine compounds. Residues of α‐ and β‐endosulfan, endosulfan sulfate, chlorpyrifos, p,p′‐dichlorodiphenyldichloroethane, p,p′‐dichlorodiphenyldichloroethylene (DDE) were detected in soils of cotton fields and in sediments from adjacent pools within the agricultural and buffer zone. Concentrations were in the range of below detection limit (DL) to 150 µg/kg dry mass (dm) for endosulfan and endosulfan sulfate together and of below DL to 12 µg/kg dm for chlorpyrifos. In pool sediments, concentrations of total endosulfan were in a range of below DL to 47 µg/kg dm. The occurrence of the pesticides was directly linked to the cotton growing season. No residues were detected at the beginning of cotton growing season. Concentration levels of p,p′‐DDE were in the range of below DL to 12 µg/kg dm. No pesticide residues were found in the protected park zone.