Quantification of Organochlorine Pesticides (ocps) Insurface Sediments

This study examines the concentrations and ecological risks of organochlorine pesticides (OCPs) in surface sediments of the lower Bomadi River. OCPs quantification was carried out using gas chromatography after extraction with 1:1 ratio of n-hexane and dichloromethane mixture by ultra-sonication. Analysis of 20 OCP congeners revealed significant variability in their concentrations across the study area. The total concentration of OCPs (Σ20 OCPs) ranged from 4.41 µg/kg at Agge to 41.8 µg/kg at Biekumogbene. Key findings include high levels of gamma-BHC at Peretorugbon, significant p,p'-DDT at Toru-Ndoro, and elevated heptachlor epoxide and endosulfan sulfate concentrations at Biekumogbene and Toru-Ndoro, respectively. The presence of these substances, alongside varying levels of DDT metabolites and chlordane isomers, indicates historical and ongoing pesticide use. Ecological risk assessment, based on the risk quotient (RQ) method, highlighted that beta-BHC, gamma-BHC, and several other OCPs pose low ecological risks (RQ < 1), while alpha -BHC, endrin, and other compounds showed moderate risks (RQ ≈ 1). Notably, delta- BHC, p,p'-DDT, and other OCPs exceeded environmental quality standards (EQS) with high RQs (> 1), signaling substantial ecological risks. These findings highlights the need for ongoing monitoring and management to mitigate the long-term ecological impacts of these persistent pollutants.