Residues and Risk Assessment of Organochlorine Pesticides in Surface Sediment of Afram River of Ghana

Abstract

The Afram River is a major tributary of the Volta Lake in Ghana that has experienced intensive agricultural activities along its banks for over 50 years. Increased agricultural activities has raised concerns of contaminants entering the river ecosystem. Sediment being a major sink of chemical pollutants in aquatic systems is therefore the target of analysis in this research. Sediment samples were analysed for organochlorine pesticide (OCP) residues. Their concentration levels and possible risk they pose to aquatic biota were assessed. Sediment samples in acetonitrile medium were sonicated on ultrasonic bath, electronically shaken, cleaned by solid phase extraction and analysed by Gas Chromatograph equipped with electron capture detector. The mean concentration ranged from 1.55 µg/kg dry weight (dieldrin) to 42.69 µg/kg dry weight (γ-chlordane).  Gamma Lindane recorded the highest incident rate of 97%. Based on sediment quality criteria of the United States National Oceanic and Atmospheric Administration (NOAA) and Canadian Sediment Quality Guidelines (CSQG), the concentrations of p,p-DDE and γ-lindane were assessed to have reached toxic levels that could present health and developmental hazards to aquatic fauna and therefore require priority remediation actions. The risk levels of p,p’-DDD, γ-chlordane, dieldrin, and endrin were also  significant enough and constitute hazard.