Title page for ETD etd-10312002-174650


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
  • bioavailability
  • non-aqueous phase liquid
  • recalcitrant compound
  • mass-transfer
Date of Defense 2002-10-14
Availability restricted
Abstract
Creosote, 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

Oneida Tie-Yard.

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