Doctor of Philosophy / Department of Civil Engineering / Alok Bhandari / Human activities generate large amounts of chlorinated phenolic chemicals that are often
introduced into the soil environment during pesticide and insecticide application, industrial
releases, and accidental spills. For example, 2,4-dichlorophenol (DCP), a derivative of the
herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) can been found in soil within 24 hours of 2,4-
D application. Horseradish peroxidase (HRP)-mediated polymerization has been proposed as an
approach to remediate soils and groundwater contaminated by phenolic pollutants. Treatment
with HRP results in the transformation of phenols into polyphenolic oligomers that sorb strongly
or precipitate on soils surfaces. Although HRP-mediated chlorophenol stabilization has been
studied extensively in surface soils, very limited scientific data is available that supports the
application of this technology in subsurface materials. Hence, the focus of this study was to
evaluate sorption and binding of DCP and products of HRP-mediated polymerization of DCP to
model geosorbents representing subsurface geomaterials. These sorbents included two humin-mineral
geomaterials and one mineral geosorbent derived from surface soils. Soil-water phase
distribution of total solute in the HRP-amended systems was observed to reach equilibrium
within 7 days in woodland humin-mineral soil (WHM), and within 1 day in agricultural humin-mineral
(AHM) and model mineral geomaterials. For all the geomaterials used, water extraction
data indicated the development of contact time-dependent resistance to extraction/dissolution of
soil-associated DCP and DPP. Solute associated with WHM geomaterial was higher at the end of
the study than that associated with AHM. Contact time increased DCP stabilization at all initial
aqueous DCP concentrations studied. Results of this study suggest that DCP stabilization in
organic geosorbents results from a combination of sorption and cross-coupling of DCP and
precipitation of DPP; in inorganic soils, precipitation of DPP macromolecules is the dominant
process. HRP-mediated stabilization of DCP in soils was effective and independent of the
solution ionic concentration. The amount of DCP stabilized in the mineral soil was comparable
to that stabilized in humin-mineral geomaterials. The research reported in this dissertation
demosntrates the potential of HRP enzyme to stabilize DCP in subsurface geomaterials under
variable contaminant and salt concentrations, thereby restricting its transport in the environment.
| Identifer | oai:union.ndltd.org:KSU/oai:krex.k-state.edu:2097/664 |
| Date | January 1900 |
| Creators | Palomo, Monica |
| Publisher | Kansas State University |
| Source Sets | K-State Research Exchange |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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