Compound-specific carbon isotope geochemistry of polycyclic aromatic hydrocarbons in eastern Newfoundland estuaries

O'Malley, Vincent Patrick (1994) Compound-specific carbon isotope geochemistry of polycyclic aromatic hydrocarbons in eastern Newfoundland estuaries. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (83MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Compound-specific carbon isotope analysis (CSIA) was performed on individual polycyclic (or polynuclear) aromatic hydrocarbons (PAH) isolated from a diverse range of environmental samples. These measurements were undertaken to determine whether CSIA could provide additional or complementary information to molecular signatures for quantitatively apportioning inputs of PAH to depositional environments. PAH extraction and purification methods suitable for CSIA were developed, and the isotopic integrity of the δ¹³C values of standard PAH taken through these work-up procedures and when exposed to a range of weathering reactions was assessed. The molecular and isotopic signatures of prominent primary and secondary sources of PAH were then characterized and quantitatively compared to the corresponding signatures isolated from St. John's Harbour and Conception Bay sediment samples. -- No significant isotopic fractionations were observed in a range of 3, 4 and 5- ring PAH taken through the sample work-up procedures. The δ¹³C values of a similar range of standard compounds was also unaffected when exposed to a series of .volatilization, photolytic and microbial degradation studies. -- The molecular signatures of the prominent primary combustion sources in eastern Newfoundland (fire and car soots) were characterized by the presence of 3, 4 and 5-ring parental PAH, whereas petroleum-related sources including crankcase oil were dominated by 2 and 3-ring parental and methylated PAH. The trend observed in the δ¹³C values of the 3, 4 and 5-ring PAH in the two combustion sources was postulated to be jointly controlled by precursor compounds in the original source material and a series of secondary reactions that occur during pyrolysis and pyrosynthesis (e.g., wood burning and car engine combustion). The significantly δ¹³C-depleted compounds observed in crankcase oil compared to the combustion sources, particularly phenanthrene and pyrene, was attributed to thermally-induced aromatization reactions of natural compounds in the oil. The aromatization of cyclic precursors (e.g., terpenoids) commonly found in virgin crankcase oil results in the production of some 3 and 4-ring PAH. -- Secondary source molecular signatures (road sweeps, untreated sewage and roadside snow) were comparable, and indicated PAH mainly of combustion origin. The application of two component (combustion vs. crankcase oil) mixing calculations using both the δ¹³C and the normalized molecular abundances indicated that PAH in the open-road sweeps and snow samples were influenced by approximately 30% inputs of crankcase oil while crankcase oil inputs to sewage were around 20%. -- PAH of combustion, petroleum and diagenetic origin were identified from the molecular characterization of St. John's Harbour sediments. From the two-component mixing calculations, approximately 70% of the overall input of PAH was identified to be of combustion origin, with vehicle emissions apparently being the dominant input source. Crankcase oil inputs account for the remaining 30% of the PAH in these sediments. However, intersample isotopic and molecular variations indicated a range of combustion contributions ranging from 50% to 90%. -- The molecular signatures of Conception Bay sediments were characterized by combustion and diagenetically-derived PAH. The observed δ¹³C variations in the 3, 4 and 5-ring compounds also indicated that the PAH were derived from a combination of at least two primary sources. However, the δ¹³C-depleted component is quite unlike crankcase oil and PAH contributions from other petroleum-related source or diagenetic origin are suggested as suitable candidates for this unknown component. -- CSIA of individual PAH was found to be highly complementary to molecular signatures in elucidating primary source inputs to depositional environments. Additionally, CSIA allows for a more quantitative approach to apportionment using the individual δ¹³C alone or in combination with the molecular abundance data and mass-balance models.

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