11 - Biodegradation of oil hydrocarbons and its implications for source identification

Abstract

Biodegradation puts a major impact on the composition of petroleum products and crude oils. This chapter discusses the fundamentals of hydrocarbon biodegradation, especially of liquid fossil fuels, and attempts to bring together the conclusions from two rather disparate areas of research. One is from the community of microbiologists and environmental scientists studying biodegradation in the laboratory and the field. The other is from the community of geochemists studying petroleum in reservoirs. Significant routes for hydrocarbons to leave the biosphere are combustion and photochemical oxidation. Photo oxidation is a very important process in the atmosphere, and while it does convert aromatic compounds in slicks to oxygenated species, it accounts for relatively little loss of nonvolatile hydrocarbons. Oxygen is both an essential reactant in the initial activation of hydrocarbons under aerobic conditions and the terminal electron acceptor for microbial growth. Most natural petroleum contains only trace amounts of alkenes. A few crude oils contain minor amounts from radiolysis, but alkenes can be quite abundant in refined products such as gasoline.