Composition and Origins of Polycyclic Aromatic Hydrocarbons in the Mackenzie River and on the Beaufort Sea Shelf

Abstract

Polycyclic aromatic hydrocarbon (PAH) concentrations in suspended particulate samples from the Mackenzie River delta and shelf sediments from the Beaufort Sea are higher than expected for a pristine area. Low concentrations of combustion PAHs indicate that anthropogenic inputs are low. Alkyl PAH distributions indicate that a significant component of the lower molecular weight parent (unsubstituted) PAH fraction is petrogenic. The majority of the high molecular weight PAHs, together with the petrogenic PAHs, have a principal source in the Mackenzie River. Despite the high PAH content, we consider the area still to be pristine. Although PAH concentrations are below the concentrations believed to induce toxic effects on biota, the high natural concentrations may make this region of the Arctic sensitive to additional PAHs from human activities. Key words: polycyclic aromatic hydrocarbon (PAH), Arctic, baseline, sediment, effects threshold, principal components analysis RÉSUMÉ. Les concentrations d'hydrocarbures aromatiques polycycliques (HAP) dans des échantillons de particules en suspension venant du delta du Mackenzie et de sédiments du plateau continental de la mer de Beaufort sont plus élevées qu'on pourrait s'y attendre pour une zone vierge. Les faibles concentrations de HAP de combustion suggèrent que l'apport anthropique est faible. La distribution des HAP alkyles indique qu'une composante importante de la fraction de HAP-mère (non substitué) à bas poids moléculaire est pétrogénétique. La majorité des HAP à haut poids moléculaire, ainsi que les HAP pétrogénétiques, ont leur source principale dans le fleuve Mackenzie. Malgré la teneur élevée en HAP, la région est toujours considérée comme vierge. Bien que les concentrations d'HAP soient inférieures aux valeurs qui pourraient avoir des effets toxiques sur le biote, les fortes concentrations naturelles peuvent rendre cette région de l'Arctique sensible aux HAP supplémentaires venant des activités humaines. Mots clés: hydrocarbure aromatique polycyclique (HAP), Arctique, données de base, sédiment, seuil des effets, analyse des principaux composants Traduit pour la revue Arctic par Nésida Loyer.

Aliphatic and aromatic hydrocarbons in tropical recent sediments of Campos dos Goytacazes, RJ, Brazil

“…This can be confirmed by the phenanthrene/alkylphenanthrenes and fluoranthene/pyrene rates (Figure 3) that characterize the organic matter from combustion origin. 5 The main compounds in this aromatic fraction are: 1,2,4a,9 -tetramethyl -1,2,3,4,4a,5,6,14b -octahydropicene (2); 2,2,4a-tetramethyl -1,2,3,4,4a,5,6,14b -octahydropicene and a tetramethyl octahydropicene. These likely were formed by diagenetic processes of precursors from higher plants.…”

“…6 For instance, the ratio between the alkyl-substituted PAH and the parent PAH can also be used to distinguish a petroleum or petrogenic source from a combustion source. 5 Biogenic PAH, detected in recent and ancient sediments have increasingly been attracting attention. Such aromatic molecular markers have mainly been identified as aromatic derivatives of natural precursors originating from bacterial lipids (hopane series), or terrestrial higher plant terpenoids 7 (amyrin series).…”

“…They can be considered biogenic PAH. 5,12,45 As may be seen in Table 2, many alkyl -tetrahydrochrysenes and alkyl -tetraoctahydropicenes were also identified. They are probably products from diagenesis, from progressive aromatization, or from loss of the A-ring followed by aromatizations of α-or β-amyrine.…”

“…1 The occurrence of polycyclic aromatic hydrocarbons (PAH) in recent materials such as soil, sediment, aerosols, water, animals and plants is of increasing environmental concern because these compounds may exhibit mutagenic and carcinogenic effects. 4 With the exception of a few minor PAH, such as cadalene, simonellite and retene, derived from higher plants, 5 the presence of these compounds in recent sediments is usually attributed to an anthropogenic origin such as car exhaust or industrial emissions. 4 The differentiation of polycyclic aromatic hydrocarbons with anthropogenic origins from those which are derived from natural sources, or by natural processes is however necessary.…”

Sedimentary record of PAHs in the Barigui River and its relation to the socioeconomic development of Curitiba, Brazil

“…Hence, the formation of PAHs depends on the reaction temperature. At relatively low temperatures (catagenesis), the distribution of PAHs is governed by thermodynamic properties, while at elevated temperatures (pyrolysis) the distribution of these compounds is dominated by kinetic characteristics (Yunker et al, 2002(Yunker et al, , 1999Yunker and Macndonald, 1995). For example, high concentrations of PAHs with more than four aromatic rings are indicative of the formation of the compounds during the pyrolysis of fossil fuels (Gogou et al, 2000) while forest, grass and prairie fires have distinct isomeric PAH distributions (Yunker et al, 2002).…”