Toxicity of bitumen on soil fertility bacteria - Nitrobacter and Nitrosomonas from Tekulu Waterside, Rivers State, Nigeria

Toxicity of bitumen on Nitrosomonas and Nitrobacter from Tekulu Waterside, Bodo in Gokana Local government area of Ogoni, Rivers State, Nigeria was carried out using standard analytical procedures. The density, API and flash point of the bitumen used in this study at 15°C was 0.9898 g/cm³, API at 60°F value of 11.46 and >200°C respectively. The total TPH and PAH constituent of the bitumen was 20,549.77 mg/L and 924.09 mg/L respectively. Analysis of the effect of different concentration (50 mg/L, 250 mg/L, 500 mg/L, 750 mg/L and 1000 mg/L) of bitumen on Nitrosomonas sp. over a period (24hrs, 48hrs. 72hrs and 96hrs) revealed that the mortality of the organism increased as the concentration of the toxicant. The mortality was also affected by the duration of exposure. The probit analysis on the lethal concentration (LC₁₀, LC₂₀ and LC₅₀) of the bitumen on Nitrosomonas sp. was 223.32 mg/L, 369.682 mg/L and 969.622 mg/L respectively and Nitrobacter sp. 587.837 mg/L, 765.74 mg/L and 1269.841 mg/L respectively, when exposed for 96 hours revealed a varying mortality status. The LC₅₀ of the bitumen on Nitrosomonas sp. peaked at 48hrs. The study shows that bitumen was more toxic to Nitrosomonas than Nitrobacter sp. based on the findings of the study, it is recommended that test organisms (Nitrosomonas sp. and Nitrobacter sp.) could serve as a potential tool for eco-toxicological assay and pollution biomarker.