GEOENVIRONMENTAL ASSESSMENT OF TOTAL PETROLEUM HYDROCARBON CONTENT IN OLOGBO FIELD, NIGER DELTA, NIGERIA

Résumé

Hydrocarbon contamination is a common phenomenon associated with oil and gas exploitation in the Niger Delta area of south-south geopolitical region of Nigeria. The aim of this paper is to assess the geoenvironmental impact of hydrocarbon spill in Ologbo area of Edo state in the Niger Delta basin using GIS with a view to drawing attention to the remediation of the area. The study area lies between longitude 05° 38’ 36.47”E to 05°4’ 26.56” E and latitude 06° 4’ 28.17”N to 06° 4’ 33.79”N. 1km2 of the study area was georeferenced, digitized and gridded at 100 m interval using Google earth imagery. Soil samples were collected at the grid intersections, at depth ranging from 0-15 cm (topsoil), 15-30 cm (mid depth) and 30-60 cm (last depth). Soil samples were analyzed using Gas Chromatogram – Flame Ionization Detector (GC-FID) instrument. The result showed that Total Petroleum Hydrocarbon (TPH) concentration at the subsurface ranged from 96.88±3.74 to 870.01 ±102.43 mg/kg, mid depth concentration was between 46.92±7.13 to 404.03±7.10 mg/kg while the last depth is between 10.74±6.62 to 106.52±23.04 mg/kg. Due to severe pollution level at intersections C, D
and E; matlab curve fitting was used to predict the maximum depth at which hydrocarbon contaminant seized to exist in the soil; the results showed that at maximum vertical depth of 460m, TPH seizes to exist in the soil (below detection level).