Levels, distribution and characterization of Polycyclic Aromatic Hydrocarbons (PAHs) in Ovia river, Southern Nigeria Isioma Tongo*, Lawrence Ezemonye, Kingsley Akpeh Laboratory of Ecotoxicology and Environmental Forensics, Department of Animal and Environmental Biology, Faculty of Life Sciences, University of Benin, Nigeria A R T I C L E I N F O Article history: Received 9 September 2016 Received in revised form 8 December 2016 Accepted 20 December 2016 Available online 21 December 2016 Keywords: PAHs Water Sediment Fish Sources Health risk A B S T R A C T The concentration and distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in surface water, sediment, and fish (Clarias gariepinus) samples collected from Ovia River, Southern Nigeria were evaluated, to assess the contamination profile of the river. The concentrations of PAHs were measured to reflect the spatial and monthly distribution of PAHs in the matrices. Mean concentrations of total PAHs ( P PAHs) in surface water samples ranged from 2.33 to 25.83 mg/L sediment, 5.25 to 573.33 mg/kg-dry weight (dw) and fish (Clarias gariepinus), 10 to 914.17 mg/kg-wet weight (ww). There was a considerable predominance of the 2 and 3-rings PAHs in all the matrices. Spatial variations showed high concentrations of PAHs in Ekenwan, the downstream station, for all the matrices. The ratios of specific PAHs compounds in sediment reflected the predominance of petrogenic PAHs sources. PAH concentrations in water were observed to be above the guideline value (0.05 mg/L) for PAHs in drinking water which calls for serious pollution concern, as this river serves as drinking water source for people of the community. Published by Elsevier Ltd. 1. Introduction Polycyclic Aromatic Hydrocarbons (PAHs) includes a large heterogeneous group of organic ubiquitous contaminants, which are formed as a result of incomplete combustion of organic materials [1]. There are several possible sources of PAHs in the environment, which are mainly through natural and anthropo- genic combustion processes. Anthropogenic activities, however, are generally considered to be major sources of PAHs in the environment [2]. Among anthropogenic factors, petrogenic and pyrolytic sources are considered to be the most important. Pyrolytic PAHs are formed as a result of incomplete combustion while petrogenic PAHs are mainly from crude oil and its refined products [3,4]. These group of compounds is of great environmental concern because of their toxic, mutagenic, and carcinogenic characteristics [1,5,6]. The widespread occurrence and accumulation of PAHs in the environment has become an issue of global health concern [7– 9]. Levels of PAHs in different environmental matrices and its associated health hazards has been reported by several authors [1,7,10–17]. The Ovia River is an ecologically and an economically important inland water body in Southern Nigeria. The river supports a large area of mangrove forests and serves as an important source of water for drinking, domestic use, and fishing, it is, therefore, vulnerable to anthropogenic influence [18]. This water body is currently contaminated with a number of pollutants [19–21]. The downstream portion of the river contains a network of pipelines arising from oil exploration and production activities, these pipelines are often vandalized resulting in oil spills. Little or no data exists on the levels of PAHs in this aquatic environment. The study was therefore carried out to determine the concentrations and distribution of PAHs in surface water, sediment and fish (Clarias gariepinus) from Ovia River, Southern Nigeria, with a view to identifying possible sources for mitigation purposes. 2. Materials and methods 2.1. Study area The study area is Ovia River in Edo State, Nigeria. The area is composed of fresh and brackish environments. The river takes its source from Akpata hill in Ekiti and flows through Ovia North and South West Local Government Area in Southern Nigeria, over a distance of approximately 200 km. The river drains into the Benin * Corresponding author. E-mail address: isioma.tongo@uniben.edu (I. Tongo). http://dx.doi.org/10.1016/j.jece.2016.12.035 2213-3437/Published by Elsevier Ltd. Journal of Environmental Chemical Engineering 5 (2017) 504–512 Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/je ce