Comparing degradation of oil alone as well as with dispersant present is critical to determine the fate and transport of these materials in the ocean.Ĭitation: Morales-McDevitt ME, Shi D, Knap AH, Quigg A, Sweet ST, Sericano JL, et al. The presence of dispersant did not dramatically change the half-lives of oil. The heterogeneity observed in all treatments was likely due to the hydrophobicity of oil and weathering processes occurring at different rates and times. Biodegradation occurred in all treatments based on the temporal decrease of the nC 17/pristane and nC 18/phytane ratios. The aliphatic half-lives for CEWAF and DECWAF treatments ranged from 0.8 to 2.0 days, but no half-life for WAF could be calculated as concentrations were below the detection limits. WAF, CEWAF and DCEWAF (a 10X CEWAF dilution) treatments half-lives ranged from 0.9 to 3.2 days for EOE and 0.5 to 3.3 days for PAH, agreeing with estimates from previous mesocosm and field studies. EOE and PAH concentrations decreased exponentially following first-order decay rate kinetics. Environmental half-lives of estimated oil equivalents (EOE), polycyclic aromatic hydrocarbons (PAH), n-alkanes (C10-C35), isoprenoids pristane and phytane, and total petroleum hydrocarbons (TPH) were determined. The water accommodated fractions (WAF) and chemically enhanced WAF (CEWAF) produced using Macondo surrogate oil and Corexit were followed over 3–4 days in controlled environmental conditions.
Mesocosm studies employing coastal and open-ocean seawater from the Gulf of Mexico were undertaken to examine changes in oil concentration and composition with time. There is a lack of understanding of the removal of oil associated with flocculate materials to the sediment. Concerns on the timing and processes associated with petroleum degradation were raised after the use of Corexit during the Deepwater Horizon oil spill.
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