DISTRIBUTION PATTERN, SOURCES AND ECOLOGICAL RISK ASSESSMENT OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) IN SEDIMENTS OF WARRI RIVER, NIGER DELTA, NIGERIA

Abstract

The distribution, pollution sources and ecological risk of the 16 priority PAHs were investigated in surface sediments of the Warri River, Niger Delta Nigeria. Sediment samples were collected from six points along the river during the wet and dry seasons. The concentrations of PAHs were determined using gas chromatography equipped with flame ionization detector after ultra-sonication with hexane and dichloromethane. The mean concentrations of the ?16 PAHs in the sediments ranged from 1158 to 1993 µg/kg for the entire study period. The concentrations of ?16 PAHs during the wet season were significantly higher than those of the dry season. The 3-ring PAHs were the dominant PAH compounds in the sediments. The sources and ecological risk of PAHs were assessed using diagnostic ratios and sediment quality guidelines (SQGs) respectively. The diagnostic ratios revealed that PAHs in the sediment of Warri River originated mainly from pyrogenic and petrogenic sources with greater inputs from pyrogenic sources. The ecological risk evaluation of PAHs in these sediments indicated low toxicity and that they would pose little or no ecological risk.