Oil spillage measures caused drastic reduction in total petroleum hydrocarbon levels in petroleum depot in Ibadan, Southwestern Nigeria

Abstract The concentrations of total petroleum hydrocarbons (TPHs) in surface water samples from ten sampling sites in the streams around the Nigerian National Petroleum Corporation (NNPC) Depot, Apata, Nigeria were examined to evaluate the environmental quality and health risks of TPH using (ninety) 90 samples. Physicochemical parameters such as pH, temperature, acidity, alkalinity, nitrate, phosphate, total dissolved solid (TDS), electrical conductivity (EC) and chemical oxygen demand (COD) were determined using standard methods. Extraction of TPHs from the water samples was achieved by liquid-liquid extraction method and quantified by gas Chromatograph Mass Spectrometry (GC-MS). Results showed that physicochemical parameters determined were within the acceptable limit except phosphate. In addition, the even-numbered aliphatic hydrocarbons (C18-C22) were higher in concentration than their odd-numbered (C15-C19). Mean TPH concentrations ranged from 0.59 ± 0.01 to 34.60 ± 5.50 ng/L were generally below target values. The health risk assessment of non-carcinogenic effects showed HQ and HI values for benzo (a) pyrene and indeno (1,2,3-cd) pyrene were less than 1.0 for adults and children, indicating no adverse effects but the sum of CR was lower than the permissible limit of 1.0 × 10−4. Although pollution was low, there is a need for monitoring and regular checks to ensure public safety.