Assessment of Phthalate Esters in the Sediment of OBA River and the Associated Ecological Risks

<p><span lang="EN-IN">Phthalate esters (PEs), widely used as plasticizers, pose global environmental risks due to toxicity and bioaccumulation. The Oba River in Ogbomoso, Nigeria, is potentially vulnerable to PEs pollution from agricultural runoff and plastic waste disposal. This study assessed PEs concentrations and ecological risks in sediments from four locations along the river: Obada, Onitinrin, Ajaawa and Iluju, with upstream and downstream samples analyzed for physicochemical properties and PEs quantified using gas chromatography–mass spectrometry. The mean values for physicochemical parameters across the sampling sites were as follows: pH (6.5–7.1), EC (0.01–0.02 mS/cm), OC (1.86–2.13%), and alkalinity (12.5–22.5 mg/L). While most parameters were within U.S. Environmental Protection Agency (USEPA) acceptable limits, alkalinity at Iluju (15 mg/L) and Onitinrin (12.5 mg/L) fell slightly below the recommended range (20–200 mg/L). PEs concentrations ranged from: DMP (0.01–0.09 mg/kg), DEP (0.29–0.92 mg/kg), DBP (2.95–7.92 mg/kg), BBP (0.36–1.92 mg/kg), DEHP (261.68–715.65 mg/kg), and DnOP (15.97–68.19 mg/kg). Notably, DEHP, DnOP, DBP, and BBP exceeded USEPA sediment quality guidelines, suggesting potential ecological risk, while DMP and DEP were present at comparatively lower concentrations. Risk quotients (0.023–0.456) show significant ecological concern, with DBP as the main risk contributor; In conclusion, Oba River sediments contain high PEs, particularly DEHP levels, warranting monitoring and remediation</span><span>.</span></p>