Asyeih Sabernejad , Abdolhadi Bashar, Marhab Rihan, Nadi Kazem, and Mehdi Hassanshahian* 1 Department of Biology, Faculty of Sciences, Shahid Bahonar University of Kerman, Kerman, Iran * Corresponding author: Mehdi Hassanshahian, Department of Biology, Faculty of Sciences, Shahid Bahonar University of Kerman, Kerman, Iran Email: mshahi@uk.ac.ir
Abstract:
Introduction: Diesel oil is the most used petroleum product in Iran and other countries. The majority of diesel oil is stored in underground reservoirs and Fuel stations. This product can heavily pollute the adjacent soil. Diesel oil pollution has some ecological effects on soil that disturb the composition and diversity of the microbial community. The present research aimed to investigate the effects of diesel oil pollution on two different types of soil. Materials and Methods: To examine the effects of diesel oil on microbial communities, two different types of soil (industrial and forest types) were collected from Kerman province, Iran. Six microcosms were designed based on three microcosms existing in each type of soil, including unpolluted microcosm, polluted microcosm, and polluted microcosm with nutrients (Nitrogen and Phosphor). Some factors were assayed in each microcosm during 120 days of the experiment. These factors included total heterotrophic bacteria, total diesel oil-degrading bacteria, dehydrogenase enzyme, and diesel oil biodegradation. Results: The quantity of diesel oil-degrading bacteria was significantly lower than heterotrophic bacteria in all soil microcosms. The quantity of diesel oil-degrading bacteria had a decrement pattern until day 60 of the experiment, but after that, these bacteria had an increment pattern. The best dehydrogenase activity between different microcosms was related to polluting microcosms with diesel oil except for farmland soil. The highest biodegradation of diesel oil in all studied soil types belonged to the industrial microcosm (95%). Statistical analysis of the results indicated a significant correlation between the most probable number quantity of heterotrophic bacteria and other assayed factors. Forest soil was significantly different from other soil types. Conclusion: Given the obtained results of the current research, that forest soil is more sensitive to diesel oil pollution, compared to industrial soil. It is, therefore, possible to propose appropriate strategies for the bioremediation of different studied soil types.
1.Introduction:
Diesel fuels are complex mixtures of saturated hydrocarbons (primarily paraffin, including n, iso, and cycloparaffins) and aromatic hydrocarbons (including naphthalene and alkylbenzene) obtained from the middledistillate, gas-oil fraction during petroleum separation1. Diesel oil pollution is an environmental problem of increasing importance. Diesel oil spills from pipeline ruptures, tank failures, various production storage problems, and transportation accidents are the most frequent causes of soil and groundwater pollution2. Soil contamination with diesel oil negatively affects the soil ecosystem, food cycle, and microbial communities3. Iran is one of the world’s oil-rich countries, and every year large amounts of diesel oil from the southern parts are extracted and refined in other areas. The release of diesel oil into the soil during transportation and refining causes pollution of soil and thus causes environmental contamination. Diesel oil pollution causes a decrease in the diversity of soil fauna and flora. Moreover, the spread of the contamination through rainwater cause polluted agricultural areas and underground water. A variety of methods have been developed to treat diesel oil contamination. While many established physical and chemical methods are efficient, they are also expensive and can cause recontamination by secondary contaminants4. Remediation of affected areas with the use of microorganisms can offer a cost-effective solution for restoring the ecosystem and can ensure clean groundwater supplies. Several researchers have reported microorganisms with enhanced oil-degrading abilities isolated from natural habitats historically contaminated with oil5. Bioremediation processes are significantly affected by the inherent capabilities of the microorganisms, their ability to overcome the bioavailability limitations in multiphase environmental scenarios (oil–water–soil), and environmental factors, such as temperature, pH, nutrients, and electron acceptor availability6. The current study aimed to study the response of the soil microbial community to diesel oil contamination. In this study, two types of soil, namely forest and industrial soil, were selected, and the response of each type of soil to diesel oil contamination was measured separately. To compare the effect of diesel oil contamination on these types of soil, some microbial and biochemical factors were assayed.
