摘要
Compositional distribution and sources of polycyclic aromatic hydrocarbons （PAHs） in Nigerian oil-based drill-cuttings have been studied for evidence of petrogenic and/or pyrogenic effects with recommendations for the strict enforcement of the ban on the use of oil-based mud in drilling by government regulatory agencies and prior bio-treatment of the drill cuttings before final fate. A 4000 g mass of the drill cuttings obtained from a mud-pit close to a just-completed crude-oil well in the Niger Delta of Nigeria, 920 g of top-soil, which served as microbes and nutrients carrier and 154g of saw dust and poultry droppings were homogenized in a 10-litre plastic container of very low thermal conductivity. The mix ratio of cuttings to top-soil to saw-dust and poultry＇ droppings was 26：6：1. Mixing and watering of the reactors were done at 3 days interval under ambient temperature of 30 ℃ for 42 days. GC-FID results showed that the total initial PAHs concentration of the drill-cuttings was 223.52 mg/kg while the initial individual PAHs concentrations ranged from 1.67 to 70.7 mg/kg, dry weight, with a 90% predominance of the combustion-specific 3-mng PAHs. The ratio of anthracene to （phenanthrene ＋ anthracene） = 0.31 was found to be greater than the 0.10 source-criterion for PAHs fraction of molar-mass 178 g/mol while the ratio of fluoranthene to （pyrene ＋ fluoranthene） = 0.40 was found to be less than the 0.50 source-criterion for fraction of molar-mass 202 g/mol suggesting that the PAHs were from pyrogenic and petrogenic sources. Pyrogenic PAHs might be from a possible local heat effect while petrogenic PAHs might be from anthropogenic petroleum fractions in proprietary oil-based mud used in drilling. However, after bioremediation by composting, the total PAHs remaining in the drill cuttings were 4.25 mg/kg （representing a 98.1% reduction）. The half-lives of the PAHs in the medium ranged from 8 to 43 days.
