RESEARCH during the last decade has demonstrate
that hydrocarbons are ubiquitous in nature. They
occur in enormous structural diversity, and the hydrocarbon
mixtures in different source materials vary
greatly in the relative contribution of their individual
components. In terms of environmental stability, hyherons
span a wide range, but most are su~ciently
persistent to participate in complex processes of dispersal,
involving transport by air, by water, by particulates
and by the food web.
Much of the past research on hydrocarbons in
nature has concentrated on saturated and olefinic
hydro~r~ns, pr~ncipalIy because of the relative ease
of analysis. By comparison, the study of aromatic
hydrocarbons has been neglected, but intensified
research efforts are now arising from the environmental
and public health questions posed by the toxicity
of many aromatics.
The terms ‘aromatic’ hydrocarbons and ‘polycyclic’
or ‘polynuclear’ aromatics (PAH) are commonly used
in an operational sense. They imply C-H compounds
containing benzenoid structures; the remainder of the
molecu&--often the largest part of it-may consist
of straight or branched chains, of olefinic groups or
of saturated rings.
This is a convenient