Hydrocarbon pollution in aquatic environments

Carbon dioxide and water are the major products from combustion of fossil fuels. Flowever, combustion is rarely totally efficient and among the products from oil 

Distributions of pyrolytic PAFls are characterized by the dominance of the non-alkylated species shown in Fig. 7.3. Particularly abundant are the highly peri-condensed compounds—such as pyrene, the benzopyrenes, benzo[gfe]perylene and coronene—that result from extensive angular fusion of benzenoid systems.The presence of such PAF1 distributions in the aromatic 

The immobilization of PAHs within the sedimentary matrix is important because many of these compounds are proven carcinogens and it would not be desirable for them to be readily released and subsequently incorporated into the aquatic food chain. Benzo[ j]pyrene is a particularly potent carcinogen and its concentration in sediments in the Severn Estuary (UK) has been estimated at 9 ppm (based on sediment 

It appears that a recognizable pyrolytic PAH fingerprint can survive over geological time-scales. Wild fires, primarily initiated by lightning strikes, are the most likely source of these PAHs in ancient sediments. Such fires have probably been a feature of terrestrial ecosystems from at least the Late Devonian (see Section 1.4.2), as suggested by the occurrence in sediments of fusinites and semifusinites (see Section 4.3.1b), the proposed products of vegetation fires (Chaloner 1989). Observed PAH distributions in ancient sediments are often like those seen in Recent sediments and are consistent with 

Pyrolytic PAH distributions in ancient sediments sometimes differ from those typical of Recent sediments in exhibiting enhanced levels of the more highly peri-condensed structures, especially benzofe]pyrene, benzo[gfe]perylene and coronene (Fig. 7.4 Killops Massoud 1992). The reasons are as yet unknown but may reflect the effects of either different formation conditions or varying geochemical processes over geological time periods. 

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