Effects of Surfactants on the Bioavailability and Biodegradation
of Contaminants in Soils
Principal Investigators
W.P. Inskeep and J.M. Wraith
Montana State University
E-mail: usswi@montana.edu
C.G. Johnston
Mycotech Corporation
Goal
This project is designed to improve understanding of fundamental
relationships between surfactant chemistry, contaminant solubilization,
and subsequent biodegradation rates in soils, while developing novel methods
which may be useful in the bioremediation of nonpolar organic compounds
in soils.
Rationale
During the past decade, much discussion has centered
on the unavailability of sorbed compounds to soil microorganisms; it is
generally now assumed that desorption and diffusion of bound contaminants
to the aqueous phase is required for microbial degradation. Furthermore,
with aging, many nonpolar contaminants form irreversibly bound residues
which are difficult to extract with nonpolar solvents and are essentially
unavailable to indigenous microbial communities or to those added as an
inoculum to stimulate biodegradation. In a recent workshop convened to
discuss major research needs in bioremediation, the bioavailability of
soil bound contaminants was consistently identified as a fundamental limitation
in enhancing rates of contaminant biodegradation in soils. One of the strategies
for enhancing desorption rates and subsequent biodegradation rates of nonpolar
contaminants in soils is the use of surfactants.
Approach
A series of contaminant partitioning studies using
a wide range of surfactants with varying structures will be performed.
Functional relationships between surfactant concentration, surfactant structure,
and extent of contaminant solubilized will be established using batch and
column studies. Effects of surfactants on subsequent biodegradation rates
of phenanthrene, PCP, DDT, and PCB will be studied under batch and transport
conditions using two representative bioremediation strategies: indigenous
microbial populations and addition of white-rot fungi. Degradation rates
will be determined under batch and transport conditions in previously unconates
fate of heavy metals in a vegetated soil and to use the model to develop
a protocol for determining the most effective vegetative planting strategies
for immobilizing heavy metals in contaminated soil.
Rationale
Abandoned sites associated with old heavy metal mining
and smelting activities often have a large proportion of their area without
vegetative cover. This allows erosional forces to proceed at a maximum
rate, and materials with high heavy metal concentrations are dispersed
by wintaminated soils with and without contaminant aging. In addition,
contaminant degradation in soil samples from several field sites contaminated
with PCP and polyaromatic hydrocarbons will be compared to controlled laboratory
experiments.
Status
Collection of eight contaminated soils has been completed
for use in surfactant experiments. These soils represent a range in
creosote/hydrocarbon
contamination. All soils are currently being characterized for chemical
content, microbiological activity, and microbial community analysis. Development
of laboratory methods for growing white-rot fungi in soil columns for use
in surfactant experiments has been conducted. A preliminary screening experiment
designed to determine the potential toxicity of biosurfactants on white-rot
fungi has been performed. To date, white-rot fungi appear to grow well
in the presence of biosurfactants. Several column transport experiments
showing enhanced transport of DDT in the presence of micelle and nonmicelle
forming surfactants have been conducted. Batch degradation experiments
of phenanthrene in the presence of model soil organic matter phases have
been performed. These experiments are designed to determine the extent
of bioavailability of sorbed phenanthrene to various substrates. This project
is in its first year.
Key Words
Surfactants, bioavailability, biodegradation, nonpolar
organic compounds.
Clients/Users
Results are of interest to other researchers,
private industry, and regulatory personnel.
Copyright © Georgia Tech Research Corporation, 1999.
All Rights
Reserved.
Make comments to: mark.hodges@gtri.gatech.edu
Last modified on: April 12, 1999.
URL: http://www.hsrc.org/