Environmental Engineering Reference
In-Depth Information
4
OIL AND RELATED CHEMICALS
What are the components of oil?
Oil is a complex combination of various hydrocarbons
(carbon-based compounds with hydrogen atoms attached).
Petroleum hydrocarbons are the primary constituents in oil,
gasoline, diesel, and a variety of solvents. Oil and related
substances don't generally mix with water (as you may have
heard) but float on the surface, although some lightweight
components (the water-soluble fraction) do dissolve, and some
evaporate. Hydrocarbons include straight-chain compounds of
various lengths, such as octane with eight carbons (Figure 4.1),
branched compounds, and compounds in which the carbons
form a ring. Aromatic hydrocarbons have alternating double
and single bonds between carbon atoms forming a six-part
ring. The configuration of six carbon atoms in aromatic com-
pounds is known as a benzene ring, after the simplest pos-
sible such hydrocarbon, benzene. Aromatic hydrocarbons can
have more than one ring, and are termed polycyclic aromatic
hydrocarbons (PAH). The smallest one is naphthalene, with
two rings (Figure 4.2).
What are polycyclic aromatic hydrocarbons (PAHs)?
Polycyclic aromatic hydrocarbons (PAHs) are major toxic com-
ponents of oil. There are thousands of different compounds
in this group; the larger molecules (with more rings) are less
soluble in water, more soluble in fats, and tend to be more
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