Study the effect of kerosene contamination on desert and farmland soil microbial community

Introduction: Kerosene is colorless liquid and slightly heavier than gasoline that specific odor removes after evaporation. The majority fraction of kerosene contains hydrocarbons between 11 to 15 carbon molecules. Farmland ecosystems may be polluted with petroleum hydrocarbons via different ways such as transportation and spill of crude oil from resource of petroleum storage. These pollutants have some effect on the texture of the soil and microbial community. The aim of this research is understands the effect of kerosene pollution on two different soils.
Material and Methods: two different soils samples were collected from desert and farmland soils. Six microcosms were designed. Indeed each soil has three microcosms such as: unpolluted microcosm, polluted microcosm, and polluted microcosm with nutrient (Nitrogen and Phosphor). Some factors were assayed in each microcosm during 120 day of experiment. These factors include: total heterotrophic bacteria, total Kerosene degrading bacteria, dehydrogenase enzyme and Kerosene biodegradation. For enumeration of heterotrophic bacteria nutrient agar medium was used. In this method serial dilutions were done from each soil and spread on nutrient agar medium then different colonies were counted. For enumeration of degrading bacteria Bushnel-Hass (BH) medium were used.
Results and Discussion:
The results of this study show that the highest quantity of heterotrophic bacteria related to farmland soil (1 × 1010). The quantities of degradative bacteria significantly were lower than heterotrophic bacteria in all soil microcosms. By passing the time if treatment from zero to 120 days two different patterns were seen in soils. In desert soil from the beginning of experiment until day 30 the increment pattern were recorded but in day 60 the remarkable decrease were observed in the quantity of bacteria. The quantity of degradative bacteria have decrement pattern until 60th day of experiment but after this day these bacteria have increment pattern. In desert soil increase in the quantity of degrading bacteria in all microcosms were recorded in day 30 of experiment. After this time the decrement pattern were observed. In farmlands soil increase in the quantity of bacteria were started from day 90 and continue until the end of experiment. The highest quantity of degrading bacteria related to farmland soil (2 × 10 6) and the lowest quantity related to desert soil ( 3 × 104). The best deydrogenase activity between different microcosms related to pollute microcosm with nutrient. The highest biodegradation of Kerosene in all studied soil belong to farmland microcosm (95 %). Statistical analysis of the results shows that there is a significant correlation between MPN quantity of heterotrophic bacteria and other assayed factors.
Conclusion: The results of this study confirmed that the selection of best bioremediation strategies belong to type of soil and in this research it was confirmed that the type of soil have significant in the percentage of degradation.