Fate, Distribution and Sources of Polycyclic Aromatic Hydrocarbons (PAHs) in Contaminated Soils in Parts of Calabar Metropolis, South Eastern Nigeria

T N Nganje,C I Adamu,K A Ibe,P A Neji,A Edet

doi:10.4314/jasem.v18i2.23

Abstract

The paper is aimed at the investigation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soils collected at depths of 15 to 100cm from two spilled sites in the vicinity of a leaking pipeline (Calabar, Nigeria). The soils were prepared in the laboratory using standard procedure and were analyzed for sixteen priority PAHs using Gas Chromatography – Mass Spectrophotometer (GC - MS).The concentration of total PAHs (TPAHs) in the contaminated soils ranged from 4.28 to 29.77mg/Kg and decreased with depth. These levels are higher than values obtained from rural and semi urban soils but lower than values obtained from soils in the vicinity of some petroleum handling facilities in part of the study area. Generally the soils were relatively enriched with medium- and lower-molecular-weight PAHs. Phenanthrene/Anthracene, Fluoranthene/Pyrene, Fluorantine/Fluorantine+Pyrene and Benzo(A)Anthracene/Chrysene ratios and the relative abundance of PAHs according to the number of rings were used to access the sources of PAHs. In addition, the main mechanism of PAHs transport in the study area was proposed.Keywords: Fate; Distribution; Sources; PAHs; Soils; contaminated soils; Calabar

Highlights

Polycyclic aromatic hydrocarbons (PAH) are widely distributed in the environment, and some are carcinogenic to human beings even at very low concentrations (Franco, 2008; Sabate et al, 2006 ;Petterson, 1989)
Concentrations of total PAHs (TPAHs) in soil: The sum of concentration of PAHs decreased with depth at the spilled sites (Fig.1) with ranges from 4.28 to 24.87mg/Kg and 6.76 to 29.77mg/Kg(site 2)
The results from the present study were compared with total PAH concentrations in soils in part of the study area (Table 1), The present study showed relatively higher total PAH concentrations than values reported by Nganje et al (2007b) and Ibe et al (2013) in the vicinities of petrol station, kerosene tank, rural and semi-urban soils, but less than values

Summary

Introduction

Polycyclic aromatic hydrocarbons (PAH) are widely distributed in the environment, and some are carcinogenic to human beings even at very low concentrations (Franco, 2008; Sabate et al, 2006 ;Petterson, 1989). PAHs are derived from natural or petrogenic sources (including geogenic, forest fires and volcanic activities) and anthropogenic or pyrogenic sources (including oil leakages, oil spills and combustion of fossil fuels). In the study area fuel spills and leakages, bush fires and refuse combustion or burning are sources through which polycyclic aromatic hydrocarbons (PAHs) are released into the environment. The release of the PAHs could take the form of major oil spillages or minor leakages of petrol from fuel storage tanks and pipelines, mechanic worksops and petrol stations (Nganje et al 2012 ,2007a)

Objectives

Methods

Results

Conclusion