CONICET | Buscador de Institutos y Recursos Humanos

Bioremediation is the tool of choice to improve contaminant elimination in soils. Since temperature is one of the mains limiting factors of these processes, only psychrotrophic and psychrophilic microorganisms are adequate for developing bioremediation processes in Antarctica and other cold areas. Although bioaugmentation has been proposed as the most effective strategy by some researchers, others have reported that optimization of physical and chemical factors of soil matrix enhance the hydrocarbon-degrading activity of the natural microflora, making unnecessary the use of bioaugmentation techniques. In Antarctica, human activity has generated some highly polluted areas nearby scientific stations. Since the extreme climate conditions as well as the international regulations prevent the use of non indigenous microorganisms, the knowledge of the autochthonous microorganisms able to use hydrocarbons as sole carbon and energy source is essential to develop bioremediation techniques in this continent. The aim of this work was to analyze the effect of bioaugmentation and biostimulation on the efficiency of in situ hydrocarbon bioremediation of chronically contaminated Antarctic soils. For this purpose, microcosms (3 kg of chronically contaminated Antarctic soil) and mesocosms (1 m2 land plots) were designed and exposed to the Antarctic climate conditions in order to evaluate: abiotic elimination, activity of autochthonous microflora, biostimulation (addition of N and P) and bioaugmentation with bacterial strains and consortia). Viable counts, hydrocarbon-degrading microorganisms, total hydrocarbon concentration (IR spectrometry) and differences in hydrocarbon patterns among treatments (GC-MS) were determined. Changes in aliphatic and aromatic fractions were inferred from p-xylene and tetradecane concentration (GC-MS) which were used as marker compounds. We found that working with chronically contaminated soils, biostimulated autochthonous microflora showed high degradation activity (81%) and resulting in similar levels compared with those where bioaugmentation were applied. Bacterial consortia previously isolated from the same contaminated area under study showed higher hydrocarbon elimination efficiency (86%) than consortia isolated from other chronically polluted Antarctic region. On the contrary, when pristine soils (without previous exposure to the hydrocarbons) were contaminated, bioaugmentation showed to be effective to improve hydrocarbon elimination. Results showed the feasibility of in situ bioremediation processes in Antarctic soils. These processes would require different strategies according to the previous exposure antecedents of the soil. A site -specificity of the hydrocarbon-degrading bacterial consortia was suggested.

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