Type of Document Master's Thesis Author Smartt, Helen Anne URN etd-10312002-174650 Title Effects of the Desorption and Dissolution of Polycyclic Aromatic Hydrocarbons on Phytoremediation at a Creosote-Contaminated Site Degree Master of Science Department Civil Engineering Advisory Committee
Advisor Name Title Novak, John T. Committee Co-Chair Widdowson, Mark A. Committee Co-Chair Berry, Duane F. Committee Member Keywords
- groundwater contamination
- non-aqueous phase liquid
- recalcitrant compound
Date of Defense 2002-10-14 Availability restricted AbstractCreosote, containing many high molecular weight hydrophobic polycyclic aromatic
hydrocarbons (PAH's), is present in the subsurface environment at the Oneida Tie-Yard
in Oneida, Tennessee. Phytoremediation using hybrid poplar trees was chosen as the
remedial technology on-site. Since monitoring began, the contaminant plume has been
shrinking consistently and evidence has shown that remediation is taking place.
However, remediation may be rate-limited by the desorption and dissolution kinetics of
the PAH's on-site.
The objectives of this research are to: (1) estimate the desorption and dissolution rates
of 10 PAH's found in the subsurface and (2) estimate the amount of each PAH and total
mass of contaminant that is irreversibly sorbed to the soil. Three laboratory desorption
and dissolution experiments were performed using contaminated soil samples from the
Oneida Tie-Yard site. The first experiment was a batch desorption equilibrium
experiment, the second was a batch desorption kinetics experiment, and the third was a
soil column dissolution kinetics experiment. The target compounds in this study were:
naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene,
fluoranthene, pyrene, chrysene, and benzo(b)fluoranthene.
The resulting data for the desorption equilibrium experiment revealed that rates of
equilibrium were truly not instantaneous in the systems studied. However, because
approximately 76% of PAH's desorbed by the first sampling event (3 days), an
equilibrium isotherm was considered appropriate. Results showed that there is a sorbed
reversible concentration that readily desorbs to the aqueous phase for each PAH.
Additionally, it was determined that the percent removal of sorbed PAH's decreases with
increasing molecular weight. Desorption curves based on experimental data were found
to exhibit linear behavior over large variations in aqueous concentration, but showed
exponential behavior as concentrations approached zero. Freundlich sorption equilibrium
isotherms for the 10 monitored PAH's on-site were generally found to have N coefficient
values over 1, especially over large variations in solution phase concentration, indicating
a non-uniform sorbent.
Dissolution of resistant PAH's under field-like conditions was determined to occur
over long periods of time. Dissolution rates calculated from experimental data were
shown to generally decrease with increasing molecular weight. Overall, desorption and
dissolution kinetics of PAH's were shown to be rate-limiting factors to remediation at the
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