Title page for ETD etd-0701102-111853

Type of Document Master's Thesis
Author Enock, Julius
Author's Email Address jenock1@lsu.edu
URN etd-0701102-111853
Title Intrinsic Biodegradation Potential of Crude Oil in Salt Marshes
Degree Master of Science in Civil Engineering (M.S.C.E.)
Department Civil and Environmental Engineering
Advisory Committee
Advisor Name Title
John H. Pardue Committee Chair
Clinton S. Willson Committee Member
William M. Moe Committee Member
  • heterotrophic microbial activity
  • soluble organic carbon
  • crude oil
  • tidal flooding
  • oil spill recurrence
  • salt marshes
Date of Defense 2002-06-21
Availability unrestricted
Understanding the influence of different perturbations on the fate of spilled oil in marine ecosystems is useful in assessing the environmental impact and remedial investigation. The effect of flooding and spill recurrence on the fate of an experimental crude oil spill (2 L/m2) was investigated using salt marsh intact cores, incubated for about 3 months, by monitoring residual petroleum hydrocarbons, heterotrophic microbial activity (fluorescein diacetate assay) and soluble organic carbon (SOC).

For the flooding study, biodegradation rate of crude oil (with half-lives varying between 16.50 and 49.51 days and turnover times between 23.81 and 71.43 days) and microbial activity increased significantly (P>0.05) in the order from continuously-flooded (CF), intermittently-flooded (IF) to non-flooded (NF) regime. The SOC increased significantly (P>0.05) in the opposite order. The results signify the influence of flooding on microbial activity and indirectly affecting biodegradation of crude oil and decomposition and accumulation of organic matter in salt marshes.

For the oil spill recurrence study (single, two, three and four successive oilings; each totaling to 2 L/m2), biodegradation rate of crude oil (with half-lives varying between 11.95 and 69.31 days and turnover times between 17.24 and 100.00 days), microbial activity and SOC increased significantly (P>0.05) with each subsequent oiling. The results suggest that, microbial degradation might not be significant in a pristine tidal marsh particularly immediate to an oil spill event as opposed to a previously contaminated one.

The lack of significant linear relationships (P>0.05) among the parameters measured in both experiments, as indicated by both (forward) stepwise regression and Pearson correlation, reflects the challenge in understanding the complex interaction of environmental factors and microbial ecology in predicting the fate of spilled crude oil in the salt marshes at least under the experimental conditions.

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