Sorption and desorption of hydrocarbons to and from historically contaminated Lake Charles sediments
Tomson, Mason B.
Master of Science
The sorption and desorption behaviors of chlorinated hydrocarbons and naphthalene to and from Lake Charles sediments were studied. The sorption of 1,2- dichlorobenzene, 1,2,4-trichlorobenzene, and naphthalene was determined to be linear via hydrophobic effect, and the partition coefficients of these compounds were in the range of literature reported values. The desorption of chlorinated hydrocarbons and naphthalene were studied with two systems--a desorption with continuous removal of aqueous phase contaminants and a desorption by the repetitive water extraction. The desorption of both historically-existed and newly-added compounds showed great deviations from the equilibrium conditions. A biphasic desorption, with a labile phase and a resistant phase, has been observed to exist for both freshly- and aged-contaminated sediments. The desorption from the irreversible compartment reached a near-constant concentration, which was orders of magnitude lower than that predicted by equilibrium equations. The size of the resistant fractions seemed highly related to the initial solid phase concentration. Several factors, including pH, temperature, and competitive sorption, were found to significantly affect the release of historically-existed contaminants from the sediments. The laboratory observations in this study agreed well with other laboratory and field observations. The existence of the irreversible fraction may have a significant impact on regulatory, modeling and remediation activities.