Soil contamination with petroleum hydrocarbons is a common problem. Toxic compounds such as BTEXs are present in gasoline derivatives. They can move through the soil and contaminate the groundwater, especially if methanol is present. This problem is critical in permeable soil. Although leaching of BTEX compounds from soil to the water is almost temperature dependent, movement of methanol through the soil is not. Methanol can move through the porous soil and reach the groundwater in a short time. It can also dissolve and carry BTEX compounds through the porous soil. Therefore, fast cleanup of the permeable soil which is contaminated with BTEX and methanol is crucial. Chlorine dioxide is an oxidizer, which is easy to use and safe to transport; and may be considered as a treatment technique for soil cleanup. Keywords: Groundwater, soil contamination, BTEX compounds, methanol, chlorine dioxide, soil cleanup

This study evaluated the efficacy of bioremediation as a treatment option for a hydrocarbon and heavy metal contaminated soil. Microbial degradation of hydrocarbons under aerobic, nitrate-reducing and sulphate-reducing conditions was examined. Nutrient supplementation with nitrogen and phosphate as well as aeration seemed to be the most important factors for enhancing biodegradation. From initial batch studies, a carbon: nitrogen ratio of 50: 1 was found to be optimal for biodegradation. However, very low carbon to nitrogen ratios were undesirable since these inhibited microbial activity. Manipulation of the pH did not seem to be beneficial with regard to hydrocarbon biodegradation. However, low pH values induced elevated concentrations of leachate heavy metals. Aerobic conditions provided optimal conditions for hydrocarbon catabolism with up to 54% of the original contaminant degraded after 2 months of treatment. Further treatment for up to 20 months did not significantly increase hydrocarbon biodegradation. Under nitrate- and sulphatereducing conditions, 6% and 31 % respectively of the initial contaminant was degraded after 2 months while after a further 20 months, 50% and 42%, respectively were degraded. The addition of soil bulking agents and the use of sparging did not significantly increase biodegradation. Similarly, the addition of inoculum did not influence biodegradation rates to any great degree. The presence of heavy metals up to concentrations of 400 mgt1 Mn, 176 mgt1 Zn and 94 mgt1 Ni did not reduce microbial activity within the soil. During the treatment phase, heavy metal and hydrocarbon migration were limited even under water saturation and low pH conditions. A Biodegradation Index was developed and evaluated and may, potentially, find use as an in situ assessment technique for microbial hydrocarbon catabolism. The iodonitrophenyltetrazolium salt assay was also found to be an effective and rapid alternative assay for monitoring bioremediation progress. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.

A variety of extractants were used to fractionate the trace metals Cd, Cu, Mn, Ni, Pb, and Zn in contaminated urban soils. The metals were mostly held in soil solid phases but not in soluble and exchangeable forms. Except for Mn, extractability of metals by selective chemicals was mainly a function of the contamination level. The speciation of these elements in water, 0.01 M CaCl2, and pH-adjusted water extra was calculated using the chemical equilibrium model MINEQL+. The free ions of Cd, Ni, and Zn were the predominant species in most of the water and 0.01 M CaCl2 extracts while PbCO30 was the main form of Pb. Organically complexed Cu accounted for over of the total dissolved Cu. The solubility of trace metals increased as solution pH was decreased. Metals Cd, Ni, Pb and Zn combined with Cl- at low pH (<5). Organically complexed Cu was shifted to Cu2+ when pH was decreased. / Except for Mn, the activities of the other metals in water, 0.01 M CaCl 2 extracts, and pH-adjusted water extracts were undersaturated with respect to established minerals in soils. MnHPO4 seems to be controlling the solubility of Mn in these extracts.

The work in this thesis demonstrates whether resins are better than conventional soil extractants at predicting plant metal concentrations, and whether low-cost soil treatments can effectively reduce metal content and concentrations in lettuce leaves. / Researchers have shown that ion exchange resins can simulate root metal uptake behaviour by acting as ion sinks. Chemical extractants on the other hand, generally do not behave in this manner. Thus, we would expect resins (in either bead or membrane form) to predict plant metal concentrations better than conventional extractants. For the first study, a procedure using anion exchange resin membranes (AEM) treated with either EDTA or DTPA chelators was chosen, since previous studies showed this method to be effective at predicting plant metal uptake, and practical for routine laboratory use. In addition, several conventional extractants were selected for comparison. / For the second part of the thesis, a study was undertaken to test the effectiveness of various food processing byproducts to stabilize metal contaminants in soils, and compare the results with those of a Na-based aluminosilicate (zeolite). (Abstract shortened by UMI.)

Urban soils are often contaminated with trace metals and the toxicity of the metals depends, in part, on their speciation in soil solutions. The objectives of this project were to estimate the metal speciation in urban soils and to evaluate the predictability of soil metal pools on plant uptake. The chemical speciation of Cd, Cu, Ni, Pb and Zn was estimated by using the Windermere Humic Aqueous Model (WHAM). In soil solutions, Cd, Ni and Zn were present mainly as free ions when the solutions were acidic and their organic complexes were dominant as the pH was over 7.5. The other two metals mostly formed complexes with organic ligands. The activities of Cd2+, Cu2+, Ni2+, Pb2+ and Zn 2+ were affected by soil pH and total soil metal burdens. All five metals were under-saturated with respect to the minerals which could potentially control the metal solubility. / Metal uptake by plants in the contaminated railway yards was generally not correlated with free, dissolved and total soil metal pools. A pot experiment demonstrated better correlations between the metal pools and the metal content in wild chicory. Multiple regression analysis showed that the metals in the leaves and roots of wild chicory could be adequately predicted by the soil total metals and soil properties such as pH and exchangeable Ca.

The extensive agricultural usage of organohalogenated pesticides has raised many concerns about their potential hazards especially in the soil environment. Environmental metabolomics is an emerging field that investigates the changes in the metabolic profile of native organisms in their environment due to the presence of an environmental stressor. Research presented here explores the potential of Nuclear Magnetic Resonance (NMR)-based metabolomics to examine the sub-lethal exposure of the earthworm, Eisenia fetida to sub-lethal concentrations of organohalogenated pesticides. Various one-dimensional (1-D) and two dimensional (2-D) NMR techniques were compared in a contact filter paper test earthworm metabolomic study using endosulfan, a prevalent pesticide in the environment. The results determined that both the 1H Presaturation Utilizing Gradients and Echos (PURGE) and the 1H-13C Heteronuclear Single Quantum Coherence (HSQC) NMR techniques were most effective in discriminating and identifying significant metabolites in earthworms due to contaminant exposure. These two NMR techniques were further explored in another metabolomic study using various sub-lethal concentrations of endosulfan and an organofluorine pesticide, trifluralin to E. fetida. Principal component analysis (PCA) tests showed increasing separation between the exposed and unexposed earthworms as the concentrations for both contaminants increased. A neurotoxic mode of action (MOA) for endosulfan and a non-polar narcotic MOA for trifluralin were delineated as many significant metabolites, arising from exposure, were identified. The earthworm tissue extract is commonly used as the biological medium for metabolomic studies. However, many overlapping resonances are apparent in an earthworm tissue extract NMR spectrum due to the abundance of metabolites present. To mitigate this spectral overlap, the earthworm’s coelomic fluid (CF) was tested as a complementary biological medium to the tissue extract in an endosulfan exposure metabolomic study to identify additional metabolites of stress. Compared to tests on the tissue extract, a plethora of different metabolites were identified in the earthworm CF using 1-D PURGE and 2-D HSQC NMR techniques. In addition to the neurotoxic MOA identified previously, an apoptotic MOA was also postulated due to endosulfan exposure. This thesis also explored the application of 1-D and 2-D NMR techniques in a soil metabolomic study to understand the exposure of E. fetida to sub-lethal concentrations of endosulfan and its main degradation product, endosulfan sulfate. The earthworm’s CF and tissue extract were both analyzed to maximize the significant metabolites identified due to contaminant exposure. The PCA results identified similar toxicity for both organochlorine contaminants as the same separation, between exposed to the unexposed earthworms, were detected at various concentrations. Both neurotoxic and apopotic MOAs were observed as identical fluctuations of significant metabolites were found. This research demonstrates the potential of NMR-based metabolomics as a powerful environmental monitoring tool to understand sub-lethal organohalogenated pesticide exposure in soil using earthworms as living probes.

The work presented in this thesis represents a contribution to the area of modeling of the transport and fate of herbicides applied to cropped fields, and was part of a larger research effort geared towards better management of herbicides. The main objective of this thesis was to develop a graphical user interface (GUI) for PESTFADE, a process-based mathematical model of pesticide transport and degradation, and to provide documentation for the execution of PESTFADE. The model simulates changes in pesticide concentration at different depths in the soil, based on relevant physical, chemical, biological and meteorological factors. PESTFADE is considered to be one of the most comprehensive models of its kind. However, it was, until now, difficult to implement due to absence of a user manual and graphical interface suitable for exploitation in a Windows environment. The author developed the GUI in Visual Basic, created macros to facilitate certain calculations, rewrote the original FORTRAN 77 code and then validated the updated version against field data obtained from an experimental site (Eugene Whelan Farm, Woodslea, Ontario). A preliminary development of an artificial neural network (ANN) to perform the same simulation implicitly, with fewer input parameters and less computational time, was also done. / The thesis describes PESTFADE and the GUI, gives guidelines for implementing the package, and presents the results of the field validation of the revised version. During this work, the author discovered that there were problems in the parts of the code dealing with sorption phenomena. This can be solved by conventional kinetics or by Gamble kinetics.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2002. / Härtill 4 uppsatser.

Diss. (sammanfattning) Umeå : Umeå universitet, 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.