ABSTRACT
Polycyclic aromatic hydrocarbons (PAH) can be formed by thermal decomposition of any organic materials containing carbon and hydrogen. During incomplete combustion or pyrolysis, PAH are supposed to be generated from small fragments via radical pathways. Once formed, PAH may undergo further pyrolytic reactions to larger PAH by intermolecular condensation and cyclization. The absolute amount of PAH formed under defined pyrolysis conditions depends, however, on the temperature as well as the material. The profile of PAH contained in fossil fuels is clearly different from that obtained by incomplete combustion or pyrolysis of organic material. In any case, the amounts of PAH possibly formed in biosynthesis will hardly be of importance in comparison to the quantities formed abiotically. PAH in fossil fuels have been formed at low temperatures by a carbonization process over millions of years. The PAH profile contained in fossil fuels is clearly different from that obtained by pyrolysis. In petroleum, the alkylated PAH outnumber the parent PAH.
