Sedimentary Records of Pyrogenic PAH Emissions from Fossil Fuel and Biomass Sources

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9708478 Eglinton This proposal was submitted in response to the Environmental Geochemistry & Biogeochemistry (EGB) solicitation, NSF 96-152. It is being jointly funded by the Divisions of Earth Sciences and Ocean Sciences and Atmospheric Sciences. The objective of this proposal is to use a newly developed method for molecular-level radiocarbon analysis to establish a 200 year record of combustion-derived (pyrogenic) polycyclic aromatic hydrocarbon (PAH) inputs to aquatic sediments. Radiocarbon represents an ideal parameter to distinguish fossil fuel (infinite 14C age)from modern biomass (contemporary 14C age) combustion sources. Exploiting these isotopic characteristics we seek to determine (a) the extent to which the proportion of fossil fuel derived pyrogenic PAH have varied since the pre-industrial age; (b) which PAH represent the most effective tracers of modern and fossil combustion sources; and c the source(s) of selected PAH of uncertain origin (perylene). Radiometrically-dated sediments with established PAH profiles from Lake Siskiwit (MI) and the Pettaquamscutt River (RI) have been selected for this study. By virtue of their remote/rural location the PAH burden in these sediments is a function of atmospheric deposition (i.e. exclusively combustion-derived inputs). Down-core PAH isotopic profiles will be used in two ways: (I)isotopic mass balance calculations will provide quantitative constraints on the contributions from different source materials; (ii) molecular 14C data will be used as a new source discrimination "vector" when plotted against concentration or compound specific 13C composition in property-property plots. The product of this novel study will be a refined assessment of the impact of anthropogenic activity on the provenance of this important class of contaminants. The data obtained may also place constraints upon temporal variations in the source(s) of other combustion products which are introduced into the environment via atmospheric transp ort, but are harder to trace (e.g. CO2, "soot" or "elemental" carbon). Finally, this study will lead to improved source apportionment capabilities and an unprecedented level of understanding of the distribution and fate of PAH in the environment. This project impinges on several aspects of environmental chemistry; it will bring together sediment, aquatic and atmospheric chemists and will employ novel molecular isotopic tools. As such we believe this study is central to the goals of the Environmental Geochemistry and Biogeochemistry program.***