| Résumé | In July 2013, a tragic incident occurred in Lac Mégantic (LM), Quebec, which led to crude oil contamination of regional surface water,soil and sediment in the LM Lake. The purpose of this study is to investigate spilled crude oil degradation potential by using the sediments from the LM Lake. In the present study, sediments collected from the spill site were used as a source of microorganisms. An aliquot of collected sediment was sterilized and used as the control of the study. Two oils having similar physicochemical properties, the LM spill source oil and Alberta Sweet Mix Blend oil (ASMB) as a reference oil, were tested for comparison purpose. This biodegradation study was performed at two different temperatures and incubation period: 22°C for 4 weeks, and 4°C for 8 weeks. The chemical composition, including total petroleum hydrocarbons (TPH), total saturate hydrocarbons (TSH), total aromatic hydrocarbons (TAH), unresolved complex mixture (UCM), polycyclic aromatic hydrocarbons (PAHs) and their alkylated congeners (APAHs), n-alkanes, and selected petroleum biomarkers, was analyzed and assessed to evaluate their potential degradation ability. Results show that there is no significant difference in degradation efficiency for the two oils used; while different incubation conditions had an impact on their biodegradation potential. For the two oils, the degradation rates followed the order of resolved components > TSH > UCM >TAH. The degradation of TPH in different carbon range followed the C10− C16 >the C16− C34 >the > C34 range. Higher temperature is favorable to the degradation of all petroleum hydrocarbons, despite that biomarker are far less biodegradable than other petroleum hydrocarbons. Specifically, almost 100% normal alkanes were degraded at 22 oC, but the degradation rates at 4 oC was less than at 22 oC, especially for pristine, phytane and some high molecular weight n-alkanes. For PAHs and APAHs, their degradation rates generally decreased with the increased number of aromatic rings and alkylated degree under the two incubation conditions, while their degradation was limited for the other 3−6 ring parent PAHs at 4 oC due to the limited bacteria activity. LM sediment can degrade contaminated petroleum hydrocarbons effectively if appropriate ambient temperature is supplied for the growth of the in-situ natural bacteria. |
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