Total petroleum and aliphatic hydrocarbons profile of the River Niger surface water at Okpu and Iyiowa-Odekpe regions in South-Eastern, Nigeria

Total petroleum hydrocarbons (TPH) as well as the aliphatic profiles of surface water at the Okpu and Iyiowa-Odekpe sections of the River Niger in South-Eastern Nigeria were determined.  Composites samples taken from surface water at three different locations (ST-1, ST-2, & ST-3) for the months of June, September, December and February, were extracted with dichloromethane (DCM) by liquid-liquid partition and analyzed for TPH and aliphatic components using gas chromatography-flame ionization detection (GC-FID). The results reveal a TPH range of 1658.475-5435.742 µg/L with a mean of 2596.523±492.466 µg/L. The mean value for the raining season (3283.783±1253.99 µg/L) was significantly higher than that of the dry season (1909.429±190.866 µg/L). Values for all the months at all sampled locations were also much higher than the European Union (EU) standard limit of 300 µg/L. Aliphatic hydrocarbon source diagnostics ratios gave range of: even to odd numbered n-alkanes ratio (0.162–2.371), carbon preference index -CPI (0.702–1.581), sum of low molecular weight to high molecular weight n-alkanes (0.0275–1.152), nC31/nC19 (0.00–49.72), sum of long chain hydrocarbons to short chain hydrocarbons (0.824–38.03), and  pristane/phytane ratio (ND–0.26); indicating that the TPH in the water were from both biogenic and anthropogenic inputs with  biogenic sources that are largely terrestrial. This calls for necessary actions to reduce the anthropogenic inputs of TPH in the water so as to protect the aquatic ecosystem and sustain public health.