Occurrence, source identification and risk assessment of polybrominated diphenyl ethers in water and sediments of Osun River, Nigeria

Abstract

In the present study, the concentrations of polybrominated diphenyl ethers (PBDEs) in water and sediments of Osun River, Nigeria were determined. The obtained water samples were subjected to liquid-liquid extraction while the sediment samples were subjected to extraction using n-hexane and acetone. The extracts were quantified using a Gas Chromatography-Mass Spectrometer to assess their distribution, source identification, and ecological risk assessments. The results of the study indicated that BDE-99, BDE-183, and BDE-209 were not detected in the water samples while BDE-28 had the most significant mean contribution (0.057 mg/L w.w) to the total PBDEs in the water samples. The sediment samples were dominated by enhanced concentrations of BDE-100 congener (mean concentration 0.184 mg/kg d.w). The compositional profiles of the PBDE congeners indicated the abundance of higher BDEs in the sediment samples compared to the water samples, a phenomenon attributed to the lower reduction rate and lower water solubility of the higher BDEs. Source identification indicated that commercial deca-BDE mixtures might represent the major source of PBDEs in the studied river. Risk assessment of PBDEs in water samples showed that the mean concentrations of tri-BDE, tetra-BDE, penta-BDE, and hexa-BDE exceeded the acceptable limits, suggesting adverse health risks to the public. Ecological risk assessment of PBDEs in sediment samples showed medium ecological risk by hexa-BDE (0.1 ≤ RQ ≤ 1) and high ecological risks due to tri-, tetra-, penta-, and deca-BDEs (RQ > 1). The study concludes that efficient and cost-effective remediation strategies should be developed and employed in the abatement of these persistent organic pollutants from the environment.