Assessment and Treatment of Hydrocarbon Inundated Soils Using Inorganic Nutrient (N-P-K) Supplements: II. A Case Study of Eneka Oil Spillage in Niger Delta, Nigeria

Polluted soils from Eneka oil field in the Niger delta region of Nigeria were collected two months after recorded incidence of oil spillage as part of a two-site reclamation programme. The soils were taken on the second day of reconnaissance from three replicate quadrats, at surface (0–15 cm) and subsurface (15–30 cm) depths, using the grid sampling technique. Total extractable hydrocarbon content (THC) of the polluted soils ranged from 1.006×10³–5.540× 10⁴ mg/kg at surface and subsurface depths (no overlap in Standard Errors at 95% Confidence Level). Greenhouse trials for possible reclamation were later carried out using (NH₄)₂SO₄, KH₂PO₄ and KCl (N-P-K) fertilizer as nutrient supplements. Nitrogen as NO₃-N and potassium were optimally enhanced at 2% (w/w) and 3% (w/w) of the N-P-K supplementation respectively. Phosphorus, which was inherently more enhanced in the soils than the other nutrients, maintained same level impact after 20 g treatment with the N-P-K fertilizer. Total organic carbon (%TOC), total organic matter (%TOM), pH and % moisture content all provided evidence of enhanced mineralization in the fertilizer treated soils. If reclamation of the crude oil inundated soils is construed as the return to normal levels of metabolic activities of the soils, then the application of the inorganic fertilizers at such prescribed levels would duly accelerate the remediation process. This would be, however, limited to levels of pollution empirically defined by such THC values obtained in this study. The data on the molecular compositional changes of the total petroleum hydrocarbon content (TPH) of the spilled-oil showed the depletion of the fingerprints of the n-paraffins, nC₈–nC₁₀, and complete disappearance of C₁₂–C₁₇ as well as the acyclic isoprenoid, pristane, all of which provided substantial evidence of degradation.