Associated petroleum hydrocarbons and heavy metals of an oil spilled site in the Niger Delta, Nigeria

Abstract

Soil samples were collected from an oil polluted site in the Niger - Delta, of the southern region of Nigeria, and were analyzed for petroleum hydrocarbons and heavy metals, which may have been introduced to the soil as a result of the oil spillage that was incidence at the site. The total extractable hydrocarbon content (THC) of 1.13×105±2.91 ×104 mg/kg of the affected soil revealed a high level of petroleum hydrocarbon contamination that far exceeds compliance limits. The gas chromatographic analyses conducted on the samples showed significant contamination in the n-C12 - n-C17 range, especially the n-C13 and n-C17 fractions, and pristane being more abundant than phytane. It also showed a significant concentration of the polycyclic aromatic hydrocarbons (PAHs) with naphthalene which may actually be oxidized before many saturates which are the most prone to biodegradation and attenuation, while
indeno 1, 2, 3 cd pyrene was the most abundant. The results also depicted a substantial concentration of the benzene, toluene, ethyl benzene and xylene (BTEX) fractions with 1, 3, dichlorobenzene as the most abundant
fraction while o-xylene had the least concentration. Heavy metals were detected in varying concentration in polluted soils. Zinc had the highest concentration of 9.84 ± 0.93mg/kg while Arsenic had the least concentration of 0.12± 0.04mg/kg. These results suggest that as at the time of sample collection, the spilled oil was still fresh on site. That
pristane was more abundant than phytane inferred an oxic depositional environment of a probable non-waxy, marine derived organic matter and a phytoplankton input for the spilled oil.