Effects of an oil spill on soil physico-chemical properties of a spill site in a Typic Paleudult of Midwestern Nigeria

Physico-chemical analysis of soil samples at an oil spill site in a Typic Paleudult of midwestern Nigeria showed that the total hydrocarbon content of top soil layers ranged from 0.6 to 12.6 ppm in the heavy impact zone and the oil had penetrated to a depth of 9.2 m. Hydrocarbon concentration in the medium impact zone ranged from 0.36 ppm while hydrocarbons were not detected in 80% of samples from the unimpacted reference zone. Measurement of heavy metal concentrations in the soil revealed a significant build-up (p < 0.05) of lead, iron and zinc in the heavy impact zone. Other parameters including electrical conductivity, exchangeable cations, available phosphorus and total nitrogen in impacted soils were comparatively low while the total organic carbon was high, compared with the reference site. Textural class of soil from the different depths showed a predominantly brown sand at the topsoil, loamy sand and grey fine sand at medium depths and red sandy clay at greater depths.