Publication Date:
2022-05-26
Description:
Submitted in partial fulfillment of the requirements for the degree of
Doctor of Philosophy
at the Massachusetts Institute of Technology
and the Woods Hole Oceanographic Institution
June 2004
Description:
The most ubiquitous source of polycyclic aromatic hydrocarbons (PAHs) to the
environment is incomplete combustion. This study generated a high-resolution historical
record of pyrogenic PAH emissions since pre-industrial times from anoxic aquatic
sediments, allowing for detailed comparison with energy consumption data. We show
that an increase in PAH concentrations over the last decade may be due to a rise in
emissions from diesel-powered vehicles. Compound-specific radiocarbon measurements
demonstrated unequivocally that the proportion of PAHs derived from fossil fuel
combustion has increased substantially during the 20th century. δ13C and Δ14C
measurements were also used to constrain the relative importance of combustion versus
in situ production as sources of perylene. In addition, a comparison of the down-core
concentration and isotopic profiles of black carbon (BC) generated by a combination of
chemical and/or thermal oxidation methods highlighted the limitations of these methods
when applied to sedimentary matrices. Finally, parallel lead and cesium isotopic records
revealed two new potential stratigraphic markers in North American sedimentary records.
206Pb/207Pb profiles show a distinct peak in the mid-19th century, while a 137Cs peak was
found to coincide with the 1986 Chernobyl accident.
Description:
Funding for this research was provided by the National Science Foundation (OCE-9708478 and CHE-0089172). The author also acknowledges support from the Brazilian
Council for Research (CNPq).
Keywords:
Carbon
;
Isotopes
;
Combustion
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
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