Molecular and Isotopic Records of Combustion Inputs to the Environment Over the Last 250 Years
WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
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The most ubiquitous source of polycyclic aromatic hydrocarbons PARs to the environment is incomplete combustion. This study generated a high-resolution historical record of pyrogenic PAR emissions since pre-industrial times from anoxic aquatic sediments, allowing for detailed comparison with energy consumption data. We show that an increase in PAR 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 PARs derived from fossil fuel combustion has increased substantially during the 20th century. deltaexp13C and Deltaexp14C 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 andor 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. 206Pb207Pb profiles show a distinct peak in the mid-19th century, while a 137Cs peak was found to coincide with the 1986 Chernobyl accident.
- Organic Chemistry