tailieunhanh - Environmental Forensics: Principles and Applications - Chapter 2

2 Chemistry and Transport of Petroleum Hydrocarbons 3800 . First documented use of asphalt for caulking reed boats INTRODUCTION An understanding of the chemistry and transport of petroleum hydrocarbons provides the foundation for forensically reviewing information dealing with petroleum hydrocarbon contamination. This chapter provides basic terminology and concepts associated with the transport and fate of crude oil and refined products in the subsurface. CHEMISTRY OF CRUDE OIL There are over one million types of hydrocarbons in crude oil, ranging from light gases to heavy residues. No two crude oils are identical. Crude oil is defined by Philip (1998) as extremely complex mixtures of saturated and. | 2 Chemistry and Transport of Petroleum Hydrocarbons 3800 . First documented use of asphalt for caulking reed boats INTRODUCTION An understanding of the chemistry and transport of petroleum hydrocarbons provides the foundation for forensically reviewing information dealing with petroleum hydrocarbon contamination. This chapter provides basic terminology and concepts associated with the transport and fate of crude oil and refined products in the subsurface. CHEMISTRY OF CRUDE OIL There are over one million types of hydrocarbons in crude oil ranging from light gases to heavy residues. No two crude oils are identical. Crude oil is defined by Philip 1998 as. .extremely complex mixtures of saturated and aromatic hydrocarbons ranging from C1toCW0 or higher plus a wide variety of compounds containing nitrogen sulfur and exycen. In addition there is also a fraction called the asphaltene fraction which is basically insoluble in ntpentane and contains a very complex matrix of high molecular weight polar compounds. Inmost cases 90 to 98 by weight of crude petroleum consists of hydrocarbons whtle the remaining materials include sulfur oxygen nitrogen and other organic eompounds. Variations in crude oil composition occur due to the nature of the source of the organic material the geologic and thermal history chemical changes that occur haring oil formation and migration and chemical alteration due to biodegradation oxidation or selective dissolution. Despite wide variations in the chemistry of crude oil the elemental compositions fall within a narrow range of elements as shown on Table 1A Neumann et al. 1981 . Crude oils have normal paraffins n-paraffins 2000 CRC Press LLC TABLE Elemental Composition of Crude Oil Element Carbon Hydrogen Sulfur Nitrogen Oxygen Composition 84-87 11-14 0-3 0-1 0-2 ranging from Cj to higher carbon numbers exist in crude oils most crude oils fall within the c5 to C30 range Schmidt 1998 . The predominant hydrocarbon classes