Improving bioremediation of phenanthrene-contaminated Antarctic soils by addition of surfactants, organic source of nutrients and a bacterial consortium

RUBERTO LAM, VAZQUEZ SC, CURTOSI A, PELLETIER E, LOBALBO A, MESTRE MC, MAC CORMACK WP

Buenos Aires

Simposio; VI Simposio Argentino y III Latinoamericanosobre Investigaciones Antárticas; 2007

Instituto Antártico Argentino

Polycyclic aromatic hydrocarbons (PAHs) are formed during low temperature combustion reactions and are widespread pollutants in the environment possessing known or suspected mutagenic and carcinogenic properties. Previous studies performed in the surroundings of Jubany station, showed a low but significant PAHs concentration in samples from 75-cm depth soils phenanthrene being one of the most represented PAHs in these soils. Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in Antarctic soils is limited by low temperatures, lack of adequate levels of nutrients, low number of PAHs-tolerant members in the autochthonous microbiota and low bioavailability of contaminants. In this way, low environmental temperature and international agreement (Antarctic Treaty) imposed the use of autochthonous cold adapted microorganisms. The addition of nutrients, mainly N and P is a common as a bioremediation strategy. Inorganic salt solutions are the most used source of nutrients. However, under environmental conditions, they could be washed quickly by rain or snow. Is for this reason that new sources of nutrients should be tested. In addition, the nutrient source should be non-toxic. In the present work, microcosms systems (performed in 1-liter glass-flasks containing Antarctic soil supplemented with 1744 ppm of phenanthrene) were used to study the effect of biostimulation with a complex organic source of nutrients (fish meal) combined with a surfactant (Brij®700).  The mixture was applied in two systems that were very different in the microorganisms content. One of them is those containing only the indigenous microflora. The other is those containing an inoculum of an Antarctic PAHs-degrading bacterial consortium.  Previous results suggested that a soil which has a previous exposition to the contaminant, as is the case of the soil involved in this study, would not require the addition of microorganism in order to improve the removal of the contaminant. We found that the combination of biostimulation with the nutrients and the surfactant and the inoculum with the bacterial consortium (bioaugmentation) caused a significant removal (46.6 %) of phenanthrene after 56 d under Antarctic environmental conditions. When bioaugmentation or biostimulation were applied separately, non-significant reduction in phenanthrene concentration was observed. Microtox® test showed a low increase in toxicity only in the most efficient system. The present results showed that “in situ” bioremediation process of phenanthrene-contaminated soils is feasible in Antarctic stations. In addition, inoculation with a psychrotolerant PAHs-degrading bacterial consortium in association with a mix of fish meal and a high molecular weight surfactant improved phenanthrene removal and should be the selected strategy when the number of hydrocarbons degrading bacteria in the target soil is low. Studies focusing in the different way of inoculation as well as in the scale- up of the culture of the bacterial consortium are in development nowadays.