Degradation of hydrocarbons in oxidized and reduced sediments

The oxidation-reduction status of Gulf Coast wetland sediment greatly influenced hydrocarbon breakdown. Degradation of ¹⁴C-labelled octadecane and ¹⁴C-labelled naphthalene was faster in oxidized (+500 mV) sediment compared with reduced (?200 mV) sediment. Naphthalene showed no breakdown in reduced anaerobic sediment. However, a shift from strict anaerobic to aerobic conditions markedly increased napthalene degradation. An oxidized layer of sediment overlying reduced sediment was identified in several zones in a Louisiana salt marsh. Hydrocarbon degradation is likely to be greater in the oxidized surface layer.