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WP20 Contaminated Harbor and River Sediment
(ARE-1118-165593) Modeling the effects of water-washing and evaporation on petroleum hydrocarbon mixture composition using comprehensive two-dimensional gas chromatography.
Arey, Jeremy1, Nelson, Robert1, Xu, Li1, Reddy, Christopher1, 1 Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, United States
ABSTRACT- Phase transfer processes such as water-washing and evaporation may drastically affect the composition and persistence of residual oil and fuel contamination in the environment. However, changes in the complex chemical compositions of petroleum mixtures resulting from these processes have not been quantitatively deconvolved or methodically distinguished from other weathering effects. By relating comprehensive two-dimensional gas chromatography (GCxGC) retention data of petroleum mixture compounds to their phase partitioning properties, we studied the impacts of water-washing and evaporation on the detailed chemical compositions of residual petroleum mixtures found in contaminated sediments of Cape Cod, MA. GCxGC provides nearly complete composition data for some complex mixtures such as petroleum hydrocarbons. However, the potential wealth of physical property information contained in the corresponding two-dimensional chromatograms has remained largely untapped. We developed a simple but robust method to estimate GCxGC retention indices for diesel-range hydrocarbons. The resulting two-dimensional retention indices were used to estimate the liquid vapor pressures, aqueous solubilities, octanol-water partition coefficients, and vaporization enthalpies of a complete set of diesel fuel hydrocarbons. Partitioning properties were typically estimated within a factor of two; this is not as accurate as previous estimation or measurement methods. However, these relationships allowed powerful and incisive analysis of phase transfer processes affecting petroleum hydrocarbon mixtures in the environment. The effects of volatilization and water-washing on petroleum mixtures were separately modeled and distinguished from other environmentally important removal processes such as biodegradation and phototransformation. Consequently, the increased resolution and physical property estimates afforded by GCxGC could significantly advance our understanding of processes that act on petroleum hydrocarbons in the environment.
Key words: petroleum, evaporation, water-washing, GCxGC
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