Bioremediation as a potential alternative for soils of EACF contaminated with petroleum hydrocarbons

Abstract

Natural environments have been affected by oil spills around the world for decades. In some cases, the attempt to cleanup can be made using physical and chemical methods. However, for the Antarctic environments this is not so simple. Displacement of the machinery necessary for the application of physical methods would be very expensive whereas the application of chemical methods would be dangerous considering the risks of additional environmental impacts. Bioremediation techniques are relatively more costeffective and benign. This technique is based on the ability of some microorganisms (especially some bacteria) to use the petroleum hydrocarbons as energy source. Considering the low-risk, the best cost-effective choice to be applied in oil-contaminated sites, presenting high rates of hydrocarbon degradation, is the monitored natural attenuation. However, in some cases, environmental factors can cause the recalcitrance of the pollutant. The more frequent cause of recalcitrance is the depletion of nutrients (especially N and P) due to input of large quantities of carbon sources (petroleum hydrocarbons). An alternative to overcome this problem is the addition of fertilizers (e.g. N-P-K, MAP, DAP). This technique is known as biostimulation. However, some precautions must be taken. For the biostimulation the most important aspect is to avoid the excess of fertilizer, which could cause side effects like eutrophication. Temperature is a critical factor for bioremediation success. In Antarctic soils, low temperatures can decrease the rate of biodegradation even when nutrients are available in satisfactory concentrations. An alternative to overcome this difficulty is to increase the number of cells of a consortium of degraders in artificial mediums under conditions of optimum growth before the introduction in nutrient-amended polluted soils. This technique is known as bioaugmentation. Theoretically, bioaugmentation is a more promising technique than biostimulation. However, the effectiveness of bioaugmentation is variable due to the low rates of survival and degrading capability of introduced microorganisms. Furthermore, in Antarctic soils the implementation of this technique is not feasible since the introduction of alien species should be avoided. An alternative to overcome these difficulties is to introduce indigenous microorganisms capable of degrading oil to the contaminated site. The purpose of the work that is being implemented is to test different doses of fertilizer in microcosms and mesocosms and to isolate and cultivate microorganisms 3