Source identification of polycyclic aromatic hydrocarbons (PAHs) in soils around crude oil contaminated area in Ohaji/Egbema, Imo State

This study aims to determine the source of polycyclic aromatic hydrocarbons (PAHs) in the soils surrounding an area in Ohaji/Egbema, Imo State, that has been contaminated by crude oil. Soil samples were collected in the study area using a soil auger at a depth of 0-20 cm at three sampling locations (sample A, sample B, and sample C) in the Mmahu community in Ohaji/Egbema. In each of the sampling locations, twenty sub-samples were collected from twenty sampling points and pooled together to form representative samples for each of the sampling locations. Prior to GC-MS analysis, the composite samples were air-dried, sieved through a 2-mm mesh, and then kept in pet bottles that had been previously cleaned. The GC-MS investigations were carried out using a Shimadzu Model 2010 GC-MS (Shimadzu, Japan) fitted with an HP-5 MS fused silica column. This was used to quantify the 16 USEPA priority PAHs in the studied soils. The sum of the 16 USEPA priority PAHs in the sample locations ranged from 0.0192 mg/kg in the control sample to 10.73 mg/kg in sample A. Compared to high molecular weight PAHs (4-6 rings), the total concentration of low molecular weight PAHs (2-3 rings) was found to be substantially greater. According to the PAH molecular diagnostic ratio, all sampling points had low to high molecular mass ratios >1, which suggests that the origin of the PAH contamination was petrogenic. The petrogenic source of contamination was attributed to oil spillage around the study area. The knowledge of source identification of PAHs in soils helps in the determination of the most appropriate remediation strategy in order to prevent further contamination and minimise the risks to human health and the environment.