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. Biodegradation of PAHs in Antarctic soils is limited by low temperatures, lack of adequate levels of nutrients, low number of PAHs-tolerants in the indigenous microbiota and low bioavailability of contaminants. In this way, low environmental temperature and international agreements (Antarctic Treaty) impose the use of autochthonous cold adapted microorganisms for in situ bioremediation. The addition of nutrients (N and P) is a common practice as bioremediation strategy. Inorganic salts are the most used source of nutrients. However, in the environment, salts could be early washed by rain or snow. For this reason, more suitable and non-toxic sources of nutrients should be tested. 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 on two different biological systems: one of them contained only the indigenous microflora and the other was inoculated with an Antarctic PAHs-degrading bacterial consortium (M10). Previous results suggested that soils having a long previous exposure to the contaminants, as is the case with the soil in this study, would not require the addition of microorganism to improve the contaminants removal. In this study we found that the simultaneous addition of nutrients, surfactant and the inoculum (bioaugmentation) caused a significant removal (46.6 %) of phenanthrene after 56 d under Antarctic environmental conditions. When bioaugmentation or biostimulation were applied separately, no significant reduction in phenanthrene concentration was observed. Microtox® test showed a slow 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 combination 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 PAHs-degrading bacteria in the target soil is low. Studies focusing on the different inoculation strategies as well as in the scale-up of the inoculum preparation are being developed nowadays.