Levels, Distribution and Sources of Polycyclic Aromatic Hydrocarbons in Surface Water in the Lower Reach of Qua Iboe River Estuary, Nigeria

Abstract

Abstract:The lower reach of Qua Iboe River estuary houses one of the largest crude oil production facility in the Niger Delta region of Nigeria. Frequent oil spills has led to severe deterioration of the water system, This study determined 16 polycyclic hydrocarbons (PAHs) in surface waters of sites across the estuary in the wet and dry seasons. Gas chromatography with flame ionization detector (GC / FID) was used to measure PAHs in water samples following extraction. The sum of PAHs ranged from7.827E-04 for the wet season to 1.500E -02 mg/l for the dry season with significantly higher (P<0.05) PAH concentration in the wet season. Total PAHs for the water sample at all sampling sites were above the permissible limit. The composition pattern of PAHs were dominated by high molecular weight PAHs, constituting 4-6 ring compounds. Diagnostic ratios of Fluoranthene/Fluoranthene + Pyrene, Anthracene/Anthracene + Phenanthrene and low molecular weight-PAH to high molecular weight PAH were calculated to evaluate possible sources of PAH compounds These ratios reflected predominantly pyrogenic sources of PAH to the water body originating from gas flaring from a petrochemical facility located close to the sampled stations. Cluster analysis was used to assess similarities between individual PAHs in water from QIRE for the dry and wet seasons. It revealed three primary PAH clusters in both seasons indicating different levels of anthropogenic activities in the cluster areas. There is a need for appropriate regulatory legislation on the control, treatment and discharge of oilfield effluents into QIRE and its adjourning creeks.