Levels of Some Polyaromatic Hydrocarbons, Heavy Metals and Capacity of Microbes Isolated from Soil Contaminated with Diesel to Utilize Hexadecane

Abstract

Soil samples contaminated with diesel were analysed to determine the bacterial and fungal diversity together with the concentration of polyaromatic hydrocarbons (PAHs) and some selected metals which are often targets in environmental checks. Bacteria and fungi were isolated and identified using standard microbiological methods. Identification and quantification of PAH, metal was accomplished using standard methods. A total of fifteen fungal species were isolated and identified. Enterobacter xiangfangensis isolated was identified using molecular tools. Degradation test using Rhizopus stolonifer and Enterobacter xiangfangensis separately was done. The fungal growth pattern revealed that there was an increase in viable cell number from 0.05 to 0.25 (80%) at 84ppm of nickel nitrate (highest). The highest bacterial count was 18.0× 10⁶ cfu/ml. The results showed that six of the USEPA target PAH assayed were detected. The concentrations of the priority pollutants in the soil samples varied from 2.08 mg/kg to 1.28 mg/kg for site 1 and 1.99 mg/kg to 1.03 mg/kg in site 2. Cd was found below detection limit. These results are valuable in addition to other reports on decontamination of sites co-contaminated. Future efforts will be aimed at determining the extent that microorganisms can utilise both heavy metals and hydrocarbons.