Comparative Ecotoxicological Evaluation of Locally Refined Diesel and Kerosene on Rhizopus stolonifer in Rivers State, Nigeria

Aim: To compare the effect of locally refined diesel and kerosene on Rhizopus stolonifer in tri aquatic bodies.

Study Design: The study employs experimental assay and statistical analysis of the data and interpretation.

Place of Study: Freshwater, brackish water, and marine water samples were collected in sterile bottles from Ugama Ekede Stream, Ugama Ekede River and at the foot of the Atlantic ocean in Udun Ama all in Andoni Local Government Area Rivers State, using sterile sampling bottles. These samples were transported to the microbiological laboratory with ice pack within 24 hours for both isolations of test organisms and toxicity.

Methodology: Standard microbiological techniques were used; toxicity testing procedures were carried out by preparing locally refined diesel and kerosene at concentrations of 0%, 5%, 10%, 25%, and 50%, tested for durations of 0 h, 24 h, 48 h, 72 h, 96 h. The cultures were incubated at 35ºC for 48 hours. LC50 was determined.

Results: The results indicate that logarithm of mortality of Rhizopus stolonifer increases with increased toxicants concentration and exposure time. The median lethal concentration (LC50) of the locally refined diesel and kerosene increases in the following order: (Note: the higher the LC50, the lower the toxic effect. Rhizopus stolonifer in locally refined diesel in fresh water (41.88%) <Rhizopus stolonifer in locally refined kerosene in fresh water (41.64.5%) < Rhizopus stolonifer in locally refined diesel in brackish water (43.28%) < Rhizopus stolonifer in locally refined kerosene in brackish water (33.41%) < Rhizopus stolonifer in locally refined diesel in marine water (40.17%) <Rhizopus stolonifer in locally refined kerosene in marine water (36.10%).

Conclusion: Locally refined kerosene in brackish water (LC50 = 33.41%) is the most toxic, having the lowest LC50 while locally refined diesel in brackish water (LC50 = 43.28%) have the lowest toxicity effect. These results show that locally refined diesel and kerosene can inhibit the growth of Rhizopus stolonifer in an aquatic ecosystem.