Q-206. Differential Changes in Microbial Communities during Bioremediation of Fuel Contaminated Desert Mining Soils in the Atacama Desert

A. Godoy-Faúndez1,2, B. Antizar-Ladislao3, L. Reyes-Bozo2, C. Sáez-Navarrete2;
1Univ. Andrés Bello, Santiago, CHILE, 2Pontificia Univ. Católica de Chile, Santiago, CHILE, 3Univ. of Edinburgh, Edinburgh, UNITED KINGDOM.

Background: The Atacama Desert has been used in a number of studies as a model of searching for life in extreme environmental conditions. Nevertheless, the effect of high loads of organic contaminants (TOC) on autochthonous microbial communities remains unknown. Fuel-contaminated areas in the Atacama Desert exist due to the occurrence of small, although repetitive spills of fuel oil during reparation and maintenance of machinery, which has been controlled using local soils and sawdust, and then contained prior to their final disposal. This study investigated the temporal changes of (i) microbial communities changes allowed to adapt to fuel contaminated soil and sawdust mixtures during two years and (ii) TOC during the bioremediation process. Methods: Composting reactors at laboratory scale, using five soil to sawdust ratios were treated under mesophilic temperature and controlled moisture content and ventilation. TOC concentration was monitored according to Standard Methods. Total microbial DNA was isolated. Terminal-restriction fragment length polymorphism and Biolog Ecoplate tests were conducted to determine: (i) the Operational Taxonomic Units (OTU), (ii) richness and (iii) diversity expressed as the Shannon-Wiener index (H´). The Average Well Color Development and profiles of utilization of C-source were determined too. Results: Different removal curves were obtained where the interaction between both sawdust and time parameters had a significant effect (p<0.050). The metabolic profiles presented correlations with the removal curves with a maximum of activity after 28 days of treatment. Differential consumption of C-sources was observed among reactors. The reactor with 100% soil presented the lowest efficiency and removal rate. Higher levels of sawdust corresponded with higher OTU numbers, diversity and removal’s rate. Conclusion: The bioremediation of an aged contaminated mixture of desert mining soils and sawdust with fuel oil is feasible. Autochthonous microbial communities adapted to fuel contaminated soils are capable of removing TOC but slowly. Metabolic profiles are an important monitoring tool presenting a differential consumption of organic sources.