Distribution Trends and Source Diagnosis of Polycyclic Aromatic Hydrocarbons (PAHs) in Sediments of Imiringi River

Ayobami Omozemoje Aigberua,Enetimi Idah Seiyaboh

doi:10.12944/cwe.16.2.25

Abstract

The environmental menace caused by hydrocarbon releasing activities on water bodies have remained a cause for great concern. Such activities are accompanied by the release of highly toxic and carcinogenic polycyclic aromatic hydrocarbons (PAH), which are easily biomagnified across the food chain, ultimately aggravating adverse health conditions in human. This study was aimed at identifying the most important environmental contributors of PAHs in sediments of the Imiringi river. Owing to the activities of oil facilities among other anthropogenic influences, water bodies are inundated with hydrocarbon pollutants which settle within river bed sediments, thereby, playing an important role in the redistribution of contaminants. The applied diagnostic ratios (Phenanthrene/Anthracene, Fluorene/Fluorene + Pyrene, Fluoranthene/Fluoranthene + Pyrene, pyrogenic index and total index) revealed the presence of mixed source of PAHs (pyrogenic and petrogenic). PAH concentrations ranged from <0.01 to 3,965.4 µg/kg with most detected compounds exceeding regulatory limits. The high molecular mass PAHs (4 - 6 ring HPAHs) represents the primary source showing 94.29% distribution, while the low molecular mass PAHs (2 - 3 ring LPAHs) recorded trace concentrations of about 5.71% of total PAHs. Principal component analysis (PCA) revealed Indeno(1,2,3-cd)pyrene and Dibenz(a,h)anthracene as principal PAH components in the environment. In addition, Pearson correlation showed Benzo(k)fluoranthene and Benzo(b)fluoranthene as the most positively correlating PAH species in sediment. Overall, the midstream section of the river was relatively more polluted than the up and down-river locations. Most notably, HPAHs recorded higher concentrations than the LPAHs. This may be due to intensive agricultural practices such as bush incineration, while waste dumps along the river bank remain tangible pyrogenic PAH contributors. On the other hand, trace amounts of observed petrogenic PAHs in some locations are possibly spill-over’s from oil bunkering activities and infiltrations from nearby oil installations.

Highlights

With around 240,000 barrels of crude oil being spilled across the Niger Delta on annual basis,[1] the water bodies of coastal communities within most of Nigeria’s offshore oil and gas installations are often faced with a myriad of environmental and infrastructure-damaging occurrences stemming from associated activities such as crude oil transport and spillage via corroded surface or under-water pipelines, boating emissions, oil bunkering, refuse dumping, industrial effluent discharges, and runoffs from coastal or riverine farmlands, amongst others
polycyclic aromatic hydrocarbons (PAH) Source Identification Ratios Ratios that were applied for the delineation of PAH sources in the environment included Phe/Ant, Flu/ Pyr, Fla/Pyr and low molecular weight PAHs (LPAHs)/HPAH (PI) (Table 1)
The reasonable level of HPAHs in the midstream section can be attributed to the high tidal movement of organic pollutants from the oil installations located upstream, coupled with the effect of bush burning from nearby farmlands, as well as leachates from waste dumps along river banks

Summary

Introduction

With around 240,000 barrels of crude oil being spilled across the Niger Delta on annual basis,[1] the water bodies of coastal communities within most of Nigeria’s offshore oil and gas installations are often faced with a myriad of environmental and infrastructure-damaging occurrences stemming from associated activities such as crude oil transport and spillage via corroded surface or under-water pipelines, boating emissions, oil bunkering, refuse dumping, industrial effluent discharges, and runoffs from coastal or riverine farmlands, amongst others These scenarios tend to elevate the levels of micro-pollutants in the aquatic ecosystem, thereby negatively impacting the overall quality of the habitat,[2,3,4,5,6,7,8] with the sediment acting as reservoir for organic and inorganic contaminants deposition. The exploration of crude oil in the region has continued to pose significant socio-economic burden on the wellbeing of local inhabitants of host communities, thereby leading to the degradation of agricultural lands and fishing zones, causing food shortage, as well as leading to communal agitations or unrest .9

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