Date of Award

2001

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Advisor

John H. Pardue

Abstract

Two types of wetland plants, a woody species, black willow ( Salix nigra), and a non-woody, the macrophyte three-square bulrush (Scirpus olneyi), were used in laboratory studies to evaluate relationships between sorption, plant uptake, translocation and transpiration of phenanthrene, a model polycyclic aromatic hydrocarbon and chlorobenzene, a model chlorinated benzene from the reversible and desorption-resistant compartment of a sediment for Phenanthrene (PHEN) and a wetland soil for chlorobenzene (CB). The wetland soil is from The Petro Processors Inc. site (PPI), a 77-acre CERCLA facility located about 10 miles north of Baton Rouge, Louisiana. Other studies have evaluated the plant uptake of non-ionic organics from hydroponic systems, however, little information exists for plant uptake of "aged" desorption-resistant contaminants in sediments. Structure activity relationships for non-ionic organics suggest that plant uptake is only effective for compounds with log Kow's from 0.5 to approximately 4, below the log Kow of 4.4 reported for PHEN. The objective of the study was to determine the potential for plant uptake of PHEN and CB. Three treatments were utilized for studies: (1) sediment with PHEN and CB aged and resistant to desorption, (2) PHEN and CB in a sand-water matrix, presumed to be fully bioavailable and (3) sediment with freshly contaminated PHEN and CB. Wetland plants were exposed to these treatments using 14C-labeled chemicals as tracers. The 14C-chemical in the plant was converted to 14CO 2 using a biological oxidizer and the radioactivity was determined with scintillation counting. The laboratory results were compared against those produced by a mathematical model to predict plant uptake taking into account sorption hysteresis which has not been considered in all previous plant uptake models. Uptake is primarily in the root and stem tissue in the sediment, and is consistent with a repartitioning from sediment to plant tissue via a simple sorption reaction. Clean, fresh wetland plant tissue represents an effective sorption phase. Results were confirmed by measuring root-water partition coefficients and computing the potential uptake based on simple partitioning.

ISBN

9780493328409

Pages

116

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