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Remediation of DDT Contaminated Soil: A Field StudyBadley , Joanne 07 1900 (has links)
<p> Point Pelee National Park in Leamington, Ontario, Canada contained a large component of private farming and recreation until the 1960's. DDT was applied at the park as pest control in the orchards and recreational areas between 1948 and 1960. Recent studies have shown that the compounds DDT, DDE and DDD are highly persistent in the shallow soils of Point Pelee National Park. A laboratory treatability
experiment has been effective in the removal of DDT, DDE and DDD from columns packed with soil collected from Point Pelee National Park, using hydroxypropyl-ß-cyclodextrin. Cyclodextrins are microbially produced cyclic oligosaccharides which have a unique hydrophilic shell and a hydrophobic cavity. They are able to form inclusion complexes and aid in the transport of relatively insoluble compounds. A pilotscale
field remediation experiment involving the application of hydroxypropyl-ß-cyclodextrin to a Random Latin-Squares design was completed at Point Pelee National Park over the course of five months. Systematic soil sampling and analyses provided DDT, DDE and DDD concentrations throughout the remediation experiment in order to assess the removal efficiency of hydroxypropyl-ß-cyclodextrin. In-Situ volumetric moisture content was monitored throughout the study with a TDR based system.
Systematic soil sampling and analyses at the conclusion of the study provided water content, organic matter content, bulk density, porosity, hydraulic conductivity as well as sampling with depth. The application of a hydroxypropyl-ß-cyclodextrin solution did result in a substantial decrease of the concentrations of DDT, DDE and DDD from the
surface soil at Point Pelee National Park. By the end of the experiment, the concentration of DDD was consistently below the regulatory limits set by the Ontario Ministry of Environment and Energy for Parkland/Recreational Land-Use. In addition to the observed decrease in concentration, there was a decrease in the degree of variation
between the measured concentrations, transport of the mass of DDT, DDE and DDD to depth and an observed tailing effect at late-times. There were also fundamental changes to the system due to the application of the cyclodextrin (HPCD) solution including an increase in moisture content and organic matter, a decrease in infiltration and a
corresponding decrease in field saturated hydraulic conductivity. There was no appreciable benefit of the application of a high concentration solution over a low concentration solution due to an observed "clogging" -effect. The results of this study indicates that further research is necessary to determine the extent of vertical mobilization
of DDT, DDE and DDD to groundwater and the role of biological matter in the observed fundamental changes responsible for the "clogging" -effect.</p> / Thesis / Master of Science (MSc)
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A Field and Modeling Study of DDT in Soil and Groundwater Following In-Situ Soil RemediationMironov, Marina 09 1900 (has links)
<p>The shallow soils of a former orchard area in Point Pelee National Park, near
Leamington, Ontario, Canada have elevated concentrations of chlorinated pesticides
above the regulatory limits. Previous studies in this area have shown that the DDT, DOE
and ODD are highly persistent with an estimated half-life of DDT in the range of 15-30
years. In 2002 a pilot-scale field remediation experiment involving the application of
cyclodextrin was conducted. This experiment resulted in substantial decrease of DDT,
DDE and DDD concentrations in the upper soil layer within the remediation grid. Soil
samples were collected within the treatment plots a year after the cyclodextrin application
was completed to assess any further changes in concentrations of DDT, DDE and DDD.
Groundwater samples were collected in the vicinity of the soil remediation grid which
provided DDT, DDE and DDD concentrations in groundwater to assess the vertical
mobilization of the compounds. Mass balance of the "soil - groundwater" system was
calculated in order to estimate the degradation rate of DDT within the remediation zone.
The 2-D unsaturated/saturated flow and solute transport numerical model
"HYDRUS 2-D" was used to gain a better estimation of DDT, DDE and DDD mass and
distribution in groundwater. The effectiveness of cyclodextrin application for remediation
of DDT contaminated soils was assessed. After remediation treatments had stopped, there
was no indication of further degradation of DDT and its metabolites in the upper layer of
soil. The groundwater concentration of DDT, DDE and DDD near the remediation grid
was 10-100 times higher than background value. This increase in groundwater
concentration is a direct indication of DDT, DDE and DDD mobilization by cyclodextrin.
The estimates of total mass of DDT in groundwater are less than 1% of mass leached
from the soil. It was concluded that the application of cyclodextrin promoted enhanced
co-metabolic biodegradation of DDT and it metabolites DDE and DDD. The estimated
half-life for the displaced DDT was less than 2 months. This work demonstrates that
cyclodextrin can be a highly effective agent for remediation of DDT contaminated soils.<p> / Thesis / Master of Science (MSc)
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