Effect of nickel on the mineralization of hydrocarbons by indigenous microbiota in Kuwait soils.

Assessment of nickel contents in soil samples in Kuwait indicated only a minor difference in concentration in hydrocarbon-contaminated (86 mg kg(-1) soil) and non-contaminated soils (84 mg kg(-1) soil). The potential inhibitory effects of nickel on the number of hydrocarbon degraders, and hydrocarbon utilization were investigated over a wide range of nickel concentrations to span concentrations observed in the soil. Nickel addition, as nickel sulphate, to soil samples reduced the number of hydrocarbon degraders in all samples by a wide range (15-96%) depending on concentration and the hydrocarbon substrate utilized. Similarly, the metabolic activities were affected as observed in mineralization (3-60%) of soils amended with various concentrations of nickel. The inhibitive effects of nickel on hexadecane and crude oil utilization were minimal but were significantly higher with naphthalene (P < 0.05) in both hydrocarbon-contaminated and non-contaminated soils. Polarographic determination of hydrocarbons induced oxygen uptake rate demonstrated the tendency of nickel to significantly inhibit (P < 0.05) the oxidation of polyaromatic hydrocarbons compared to aliphatic hydrocarbons.