Attenuation of petroleum hydrocarbons by weathering: a case study

Possible alterations in the distribution and composition of total petroleum hydrocarbon (TPH), polycyclic aromatic hydrocarbons (PAHs), and benzene, toluene, ethyl benzene, and xylene isomers (BTEX) in the released oil at Idu-Ekpeye in Niger Delta (Nigeria) were studied within two seasonal variations of two months and six months, with a view to assessing the level of attenuation of these hydrocarbons in impacted soils. Although there were significant contaminations in the kerosene range (n-C10-n-C14) two months after, especially of the n-C12 and n-C13 fractions, the complete disappearance of the n-C8 to n-C23 hydrocarbons, including the acyclic isoprenoids (pristane and phytane), and the reduced amounts of PAHs, and BTEX, six months after, provided substantial evidence of attenuation as indicated in the reduction in total hydrocarbon content (THC) from 61.17 to 42.86%. Soil physicochemical properties such as pH, moisture content, heavy metal, TOC, and TOM, all provided corroborative evidence of hydrocarbon attenuation. The pristane/phytane ratio of the spill samples suggests that the spilled oil was genetically oxic.