Behavior of a chemically dispersed oil in a wetland environment

An experiment was conducted at a wetland research facility, investigating the behavior and effects of chemically dispersed oil (CDO) using an oil-spill dispersant. The research site is located on the San Jacinto River near Houston, TX. The replicated treatments included oiled control, “high-dose” CDO (1:10 dispersant-to-oil ratio (DOR)), “low-dose” CDO (1:20 DOR), as well as an unoiled control. Known amounts of oil or dispersed oil were added to the respective plots. Sediment samples were taken over a 99-day period using a 5-cm-diameter coring device. The GC/MS results for both “total target saturate hydrocarbons” and “total target aromatic hydrocarbons” were plotted over time and data were modeled using nonlinear regression. The overall (including abiotic and biotic) petroleum loss rates for the dispersed-oil treatments were not statistically different when compared to the oiled control. However, the initial concentrations for the dispersed-oil treatments were statically lower (95% confidence) than for the oiled control. From this, it can be inferred that the dispersed oil was more prone to flush off the sediments, as was visually observed. Biodegradation rates were also determined for all treatments; it was concluded that there were no differences when comparing each dispersed-oil treatment to the oiled control. The sediments from each plot were also analyzed for microbial population numbers (most-probable-number) and acute toxicity (Microtox ® 100% Test). Statistical analyses for both sets of data found no significant differences for the dispersed-oil treatments when compared to the oiled control.