ASSESSMENT OF PHTHALATE ESTERS IN THE SEDIMENT OF OBA RIVER AND THE ASSOCIATED ECOLOGICAL RISK

Phthalate esters (PEs) are esters of benzene 1-2-dicarboxylic acid. They are widely used as plasticizers in plastic production for flexibility and durability. The contamination of sedimante by phthalate esters is a growing global concern due to ita toxicity and jertential biscumulation in aquatic ecosystems. Oba River is at risk of phthalate esters pollution as a result of discharge of agricultural rumort, and indiscriminate disposal of plastic wastes along the course. This study therefore aimed to assess the pollution load of phthalate esters and associated ecologiest niek in Oha River at Ohada, Onitinrin, Ajaawa and Huju, Ogbormoso, Southwest, Nigeria Two composite sediment samples were collected from upstream and downstream at each sampling location 200m away from each other. These samples were analyzed for their physicochemical parameters like Potential of Hydrogen (p1), Electrical Conductivity (C) Organic Carbon (OC), and Alkalinity, using electrometrie method, while phthalate esters were determined by Gas Chromatograph Mass Spectrometer (OCMS). Pollution index was calculated to evaluate extent of pollution. Risk Quotient was also calculated to evaluate the associated ecological risk using Universal Standard Environmental Protection Agency (USEPA) model. The mean concentration of physicochemical parameters in Huju, Onitinrin, Obada and Ajaawa, ranged from pll (6.5-7.1), EC (0.01-0.02ms/cm), OC (1.86-2.13%), Alkalinity (12.5-22.5mg/L) which indicate that all were within the USUPA permissible range across all sites except alkalinity which is within the USEPA permissible range (20-200 mg/L) in two out of the four locations, with lujo (15 mg/L) and Onitinrin (12.5 mg/L) slightly below the permissible limit. The levels of Phthalate Esters across all the four sites were in the range of DMP (0.01-0.09mg/L), DEP (0.29-0.92mg/L), DBP (2.95.7.92mg/L), BBP (0.36-1.92mg/L), DEHP (261.68-715.65mg / L ), DnOP (15.97- 68 .19mg / L) for all sites (Iluju, Onitinrin, Obada and Ajaawa). Therefore all DEHP. DnOP, DBP and BBP levels were above the USEPA limit indicating that the sediment can pose danger to aquatic life while DMP and DEP levels are relatively low, suggesting low contamination levels with respect to two congeners. The risk quotient ranged (0.046 * 1786.76mg / l) (0.026 - 1274.81mg / l) (0.3 - 1394.38mg / 1) and (0.02 - 1134.81mg / l) in Iluju, Onitinrin, Obada, and Ajaawa respectively. Therefore, the results indicate significant risks associated with phthalate esters in sediments at all sites, particularly due to DEHP. In conclusion, the sediment contains significant levels of phthalates esters which are above the USEPA acceptable limits. Hence it is recommended that regular monitoring and possible remediation efforts are necessary, particularly in the sites with high DEHE concentrations.