Influence of nutrients addition and bioaugmentation on the hydrocarbon biodegradation of a chronically contaminated Antarctic soil.

Complexity involved in the transport of soils and the restrictive legislation for the area makes on-site bioremediation the strategy of choice to reduce hydrocarbons contamination in Antarctica. The effect of biostimulation (with N and P) and bioaugmentation (with two bacterial consortia and a mix of bacterial strains) was analysed by using microcosms set up on metal trays containing 2.5 kg of contaminated soil from Marambio Station. At the end of the assay (45 days), all biostimulated systems showed significant increases in total heterotrophic aerobic and hydrocarbon-degrading bacterial counts. However, no differences were detected between bioaugmented and nonbioaugmented systems, except for J13 system which seemed to exert a negative effect on the natural bacterial flora. Hydrocarbons removal efficiencies agreed with changes in bacterial counts reaching 86 and 81% in M10 (bioaugmented) and CC (biostimulated only) systems. Results confirmed the feasibility of the application of bioremediation strategies to reduce hydrocarbon contamination in Antarctic soils and showed that, when soils are chronically contaminated, biostimulation is the best option. Bioaugmentation with hydrocarbon-degrading bacteria at numbers comparable to the total heterotrophic aerobic counts showed by the natural microflora did not improve the process and showed that they would turn the procedure unnecessarily more complex.