Microbial degradation potential of some Ghanaian soils contaminated with diesel oil

The experiment was conducted in the laboratory to investigate the degradation of diesel oil in four soils obtained from semi-deciduous forest (Bekwai and Kokofu series) and savanna (Toje and Nyankpala series) zones with the aim to assess the degrading potential of these soils. The soils were contaminated with diesel oil at 10 g oil /kg soil. The contaminated soils were incubated under room temperature and sampled for total aerobic heterotrophic (TAH) bacterial counts, hydrocarbon utilizing bacterial (HUB) populations, and quantity of diesel oil degraded. The TAH bacteria and HUB counts in all the soils increased in response to diesel oil contamination. The TAH bacteria counts in the forest soils took a longer time to reach their peaks than the savanna soils. The cumulative diesel oil degraded gave an upward trend during the period of study. Between 15 and 40 days after incubation the forest soils (Bekwai and Kokofu) degraded more oil than the savanna soils (Toje and Nyankpala). This study revealed that the main factors responsible for differences in degrading abilities of these soils are presence of large populations of hydrocarbon utilizing bacteria, availability of organic carbon, nitrogen and phosphorus. The study also therefore indicated that the Ghanaian soils used in the present investigation have the potential of degrading diesel oil.