Effect of dispersants on the biodegradation of South Louisiana crude oil at 5 and 25 °C

This article reports biodegradation rates for a commercial dispersant, JD-2000, South Louisiana crude oil (SLC) alone, and SLC dispersed with JD-2000 at 5 and 25 °C. Results from the biodegradation experiments revealed that Component X, a chemical marker for JD-2000, rapidly degraded at both temperatures. The application of JD-2000 decreased by half the overall biodegradation rate of aliphatic compounds at 25 °C. At 5 °C, a residual fraction consisting of iso- and n-alkanes (C29–C35) persisted after 56 d. The combination of dispersant and higher temperature resulted in faster removal rates for 2- and 3-ring polycyclic aromatic hydrocarbons. When compared with Corexit 9500, our results suggest that the chemistry of the surfactant (or surfactants) in JD-2000 might have favored oil dissolution (substrate transport to the aqueous phase) as an uptake mechanism over adhesion, which requires direct contact of the biomass with the oil. •Biodegradation of light crude oil dispersed with JD-2000 by indigenous microorganisms.•Comparison with tests conducted with Corexit 9500.•The different roles of the two dispersants in microbial degradation.•Biodegradability of surfactant ingredients in JD-2000 and Corexit 9500.