Dầu thô là một hỗn hợp rất phức tạp, có chứa hàng trăm hàng ngàn hydrocarbon (Cooney, 1980). Các hợp chất trong dầu thô có thể được chia thành ba lớp bao gồm các hydrocarbon bão hòa, các hydrocarbon thơm, và cực hữu cơ | Section 3 Biodegradation Mineralization Biotransformation Bioaccumulation of Petroleum Constituents and Associated Heavy Metals CHEMICAL COMPOSITION OF FUEL OILS NAPHTHA KEROSENE FUEL OIL AND DIESEL 2 Table lists organic compounds found in diesel fuel 2 as reported by Clewell 1981. GASOLINE Tables through list the organic compounds and trace elements found in gasoline as reported by different references. JP-5 Tables through list the organic compounds and trace elements found in JP-5 as reported by different references. JP-4 Tables through list the organic compounds and trace elements found in JP-4 as reported by different references. ORGANIC COMPOUNDS Crude oil is a highly complex mixture containing hundreds of thousands of hydrocarbons Cooney 1980 . Compounds in crude oil can be divided into three general classes consisting of saturated hydrocarbons aromatic hydrocarbons and polar organic compounds Huesemann and Moore 1993 . Saturated hydrocarbons can be separated further into straight-chain and branched alkanes as well as cyclic alkanes with varying numbers of saturated rings and side chains. Aromatic hydrocarbons contain one or more aromatic rings ranging from simple monoaromatic compounds such as benzene and toluene to polyaromatic compounds such as pyrene. The polar fraction is made of compounds containing polar heteroatoms such as nitrogen sulfur and oxygen. Refined oils are also complex for example kerosene may contain as many as 10 000 different hydrocarbons Sharpley 1964 . This complexity also extends to other petroleum products Atlas 1977 . For microorganisms to biodegrade petroleum completely or attack even simpler refined oils thousands of different compounds must be metabolized. The chemical nature of these petroleum components varies from the simple M-paraffin monoalicyclic and monoaromatic compounds to the much more complex branched chains and condensed ring structures Horowitz
