An emplaced source of coal tar creosote within the sandy Borden research aquifer has provided an opportunity to document the long term (5140 days) natural attenuation for this complex mixture. Plumes of dissolved chemicals were produced by the essentially horizontal groundwater flowing at about 9 cm/day. Eleven chemicals were extensively sampled seven times using a monitoring network of ~280 14-point multilevel samplers. A model of source dissolution using Raoult’s Law adequately predicted the dissolution of nine of eleven compounds analysed. Mass transformation has limited the extent of the plumes as groundwater flowed more than 500 m yet the plumes are no longer than 50 m. Phenol and xylenes were removed and naphthalene was attenuated from its maximum extent on day 1357. Some compound plumes reached an apparent steady state and the plumes of other compounds (dibenzofuran and phenanthrene) are expected to continue to expand due to an increasing mass flux and limited degradation potential. Biotransformation is the major process controlling natural attenuation at the site. The greatest organic mass loss is associated with the high solubility compounds. However, the majority of the mass loss for most compounds has occurred in the source zone. Oxygen is the main electron acceptor yet the amount of organics lost cannot be accounted for by aerobic mineralization or partial mineralization alone. After 10 years the source zone was treated with permanganate in situ to reduce the flux of contaminants into the dissolved plume and to permit natural attenuation to further reduce the plume extent. A sufficient mass of permanganate was injected to oxidize ~10% of the residual source. Laboratory experiments demonstrated that eight of ten of the study compounds were readily oxidized by permanganate. Once treated oxidized compounds displayed a reduced plume mass and mass discharge while they migrated through the monitoring network. Once beyond the monitoring network the mass discharge and plume mass of these compounds returned to pre-treatment trends. Non-reactive compounds displayed no significant decrease in mass discharge or plume mass. Overall the partial in situ chemical oxidation of the coal tar creosote source produced no long-term effect on the dissolved plumes emanating from the source.

No description available.

Currently, creosote-treated wood waste is mainly landfilled but the Province of Nova Scotia would prefer to see the waste converted to a valuable product. Bioremediation provides a treatment option for creosote-treated wood waste and the production of a value-added product that would have economic and environmental benefits. Composting technique can be used to degrade the contaminants and convert wood waste into humus and nutrients rich product and reduces the waste volume. The aim of this study was, therefore, to test the efficiency of the composting process in degrading the creosote in the contaminated wood waste. A laboratory scale bioremediation process was carried out in three specially designed in-vessel bioreactors equipped with thermo-insulating outer layer, mixing units, controlled aeration units, thermocouples a data logger and a computer. The three bioreactors were used as replicates. The ability of three thermophilic and cellulolytic microorganisms (T. curvata, T. aurantiacus and T. fusca) to degrade lignocellulose substrate was tested.

No description available.

No description available.

In 1990, creosote contamination was discovered at the location of a railroad tie treatment facility active in the 1950s until 1973. In 1997, a phytoremediation field study was implemented with the planting of 1,026 hybrid poplar trees and 36 cells of vegetated and unvegetated grass and legume treatments. The hybrid poplar tree phytoremediation system was designed to control infiltration and groundwater flow and enhance subsurface remediation. The grass phytoremediation system was designed to control erosion and enhance surface soil remediation. The overall objectives of this study were to: (1) assess the extent of subsurface remediation, (2) determine the mechanisms of remediation attributable to the hybrid poplar tree phytoremediation system and microbial degradation, (3) assess the effects of the grass phytoremediation system on surface soil remediation, and (4) determine the mechanisms of surface soil remediation resulting from the grass phytoremediation system. / Master of Science

Ten strategically placed push-pull wells were installed to determine in-situ degradation rates at a creosote contaminated site and to assess the contribution of hybrid poplar trees to polynuclear aromatic hydrocarbon (PAH) remediation. Well positioning enabled comparison between contaminated and non-contaminated locations, as well as comparisons between locations with and without trees. Comparison of areas with and without trees enabled an improved understanding of the role that the phytoremediation system has on the overall degradation of PAHs at the site. Bromide, a conservative, non-reactive tracer, was injected in solution along with dissolved oxygen. Twelve push-pull tests (PPTs) were performed, of which three did not include naphthalene in the injection solution, so that the developed method could be evaluated, tested, and yield an initial set of rates to make seasonal and spatial varying in-situ comparisons. Method comparison used for rate analysis found the highest confidence in the method of Snodgrass and Kitanidis (1998) for zero order rates and the method of Haggerty et al. (1998) for first order rates. The largest zero and first order rates, 2.43 mgnaphthalene/L-hr and 1.25 1/hr, respectively, occurred at treed regions in June. Zero and first order winter rates at treed regions were greater by a factor of at least 2.5 when compared to non-treed regions. Degradation rates at treed regions were found to steadily increase by over four times from winter to summer. Results validate that decay variations attributed to phytoremediation can be detected with the push-pull method. PPTs performed at the Oneida site verified observed trends determined from six years of monitoring data, microbial characterization, and microcosm studies. / Master of Science

There are many methods for cleaning up contaminated soil and groundwater. Phytoremediation is an engineered method that utilizes plants and trees to remove or immobilize inorganic and organic contaminants. The plants and trees can contain contaminant plumes, uptake the contaminants, or aid in the degradation of the contaminants through several poorly understood mechanisms. Hybrid poplar trees were planted to contain a creosote contaminant plume at the study-site in Oneida, Tennessee. This research looks at how the trees will affect groundwater flow in the site. This is accomplished with the groundwater modeling program MODFLOW. The trees are simulated using the Evapotranspiration Package within MODFLOW, within the GMS modeling platform, to produce a two-dimensional unconfined aquifer viewpoint groundwater model. Site characterization, setup, and rationale are provided. The modeling methodology including calibration, sensitivity analysis, non-unique solution check, and verification are also provided. The modeling methodology included steady-state model calibration at the study-site to match observed field data; precursory steady-state and subsequent practice transient calibrations at the site; and incorporation of the simulation of evapotranspiration in the final transient model calibrations at the site. The results show that a phytoremediation system consisting of densely-planted hybrid poplar trees can indeed impact groundwater flow, although not to the extent that clearly would contain a creosote contaminant plume. Various input parameters including specific yield, transient recharge, starting heads, evapotranspiration rates, and evapotranspiration extinction depths impacted MODFLOW model sensitivity in transient calibrations. Varying the time steps in post-precipitation stress periods did not significantly impact the model output. The interception trench conductance played a minimal role in the calibration, but trench groundwater collection data was lacking, and the trench was frequently in need of maintenance. Further suggested data requirements include more frequently collected rainfall and piezometer data, as well as the installation of more piezometers outside the model domain contained in this study. Using the Evapotranspiration Package in MODFLOW provided more realistic and authentic results than using the Well Package (used in a previous study of the site by Panhorst in 2000) to simulate evapotranspiration. The Evapotranspiration Package in MODFLOW incorporates transpiration extinction depths that prevent transpiration when the water table drops below a certain depth. Further suggested program development includes incorporating an asymptotic function for transpiration rates and allowing the Evapotranspiration Package to import evapotranspiration rates, extinction depths, and elevations. It may be deduced from this impact of flow that the tree system will aid in containment of a contaminant plume, but at the trees current growth stage, and with the coal layer present at the site, the containment is limited. / Master of Science

Phenology of tetraploid Larrea tridentata was studied at four sites, one east and three west of Tucson, Pima County, Arizona in 1972-1974 and 1981. Leaf initiation, stem elongation, flower buds, flowers, maturing fruits and mature fruits were recorded at regular intervals on a sample of 10 tagged plants at each site. Quantitative production of maturing fruits on each sampled plant was estimated during the 1981 spring and summer seasons. The time required for individual new flowers to develop into mature fruits was determined for 1981. These phenological data were related to precipitation and temperature during 1972-1974 and 1981. Leaf initiation and stem elongation were continuously active on at least some parts of all sampled plants throughout the study, indicating year-round vegetative growth of Larrea in this part of the Sonoran Desert. One or more of the four reproductive phenophases were present throughout the 1972-1974 and 1981 periods. Flower buds were initiated during any time of the year. Spring flowering was the most dependable, summer flowering was frequent but less consistent and fall and winter flowerings were occasional, irregular and far more variable. Spring flowering persisted longer than summer flowering. Maturing fruit production was much greater in the spring than in the summer. Approximately 53 to 65 days were required in the spring and 42 to 47 days in the summer for new flowers to develop into mature fruits. Active vegetative growth invariably preceded the renewal of any reproductive activity. The emergence of flower buds appears to be triggered and sustained by the availability of sufficient soil moisture with minimal influence by temperature. However, higher temperatures tend to speed up the development of flower buds and flowers and fruit maturation. Differences in phenological responses among the four study sites appear to be caused mainly by local fluctuations in precipitation. The year-round vegetative growth activity and the frequent recurrence of reproductive activities observed in this study represent adaptive responses of Larrea to the biseasonal regime and the moderate winter temperatures characteristic of the northeastern portion of the Sonoran Desert.

No description available.