Surveillance and source diagnostic investigation of hydrocarbon residues in sediments.

The nature and seasonal distribution of hydrocarbons were studied in Ondo coastal region in Western Nigeria. The petroleum hydrocarbons were screened by gas chromatography with flame ionization detector (GC/FID) and gas chromatography-mass spectrometry (GC-MS). Complex series of compounds were identified. The overall molecular compositions obtained were characteristic of petrogenic origin with very little biogenic input. The concentrations of two important polycyclic aromatic hydrocarbons (PAHs); phenanthrene and anthracene exceeded the threshold level where adverse effects on biota would occasionally occur; a conclusion suggested to be clarified by site-specific studies on resident organisms. The study is useful for ecological risk assessment in the context of contaminant input, nature, pattern and trend.