Thesis (Ph. D.)--Mississippi State University. Department of Civil Engineering. / Title from title screen. Includes bibliographical references.

Thesis (Ph.D.)--University of Alberta, 2009. / Title from PDF file main screen (viewed on Feb. 19, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Geotechnical Engineering, [Department of] Civil and Environmental Engineering, University of Alberta. Includes bibliographical references.

Respirometric experiments were performed to evaluate the role of nitrogen in aerobic diesel biodegradation. Specific objectives included 1) evaluating the effects of water potential induced by various nitrogen amendments on diesel biodegradation rates in arid region soils, 2) comparing concurrent effects of C:N ratios and soil water potential on diesel degradation rates, and 3), measuring gross rates of nitrogen cycling processes in diesel-contaminated soil to determine duration of fertilizer bioavailability. In all studies, increasing nitrogen fertilization resulted in a decrease in total water potential and correlated with an increase in lag phase and overall reduction in microbial respiration. Highest respiration and estimated diesel degradation was observed in the 250 mg N/kg soil treatments regardless of diesel concentration, nitrogen source, or soil used, suggesting an inhibitory osmotic effect from higher rates of nitrogen application. The depression of water potential resulting in a 50% reduction in respiration was much greater than that observed in humid region soil, suggesting higher salt tolerance by microbial populations of arid region soils. Due to the dependence on contaminant concentrations, use of C:N ratios was problematic in optimizing nitrogen augmentation, leading to over-fertilization in highly contaminated soils. Optimal C:N levels among those tested were 17:1, 34:1, and 68:1 for 5,000, 10,000 and 20,000 mg/kg diesel treatments respectively. Determining nitrogen augmentation on the basis of soil pore water nitrogen (mg N/kg soil H₂0) is independent of hydrocarbon concentration but takes into account soil moisture content. In the soil studied, optimal nitrogen fertilization was observed at an average soil pore water nitrogen level of 1950 mg N/kg H₂0 at all levels of diesel contamination. Based on the nitrogen transformation rates estimated, the duration of fertilizer contribution to the inorganic nitrogen pool at 5,000 mg/kg diesel was estimated at 0.9, 1.9, and 3.2 years in the 250, 500, and 1000 mg/kg nitrogen treatments respectively. The estimation was conservative as ammonium fixation, gross nitrogen immobilization, and nitrification were assumed as losses of fertilizer with only gross mineralization of native organic nitrogen contributing to the most active portion of the nitrogen pool.

Improving food safety and food security is imperative to adequately feed a growing population that is expected to exceed 9 billion people by 2050. Mushroom cultivation provides unique opportunities to take advantage of underutilized resources and produce high-quality food from otherwise inedible or unsafe food sources. Pleurotus ostreatus is a ligninolytic and biotechnologically relevant fungus that can be cultivated on a diverse array of lignocellulosic byproducts. Prosopis spp. are abundant in the Sonoran Desert and broadly distributed in semi-arid to arid regions around the globe. Prosopis spp. legumes (pods), and approximately 25% of all commonly cultivated crops, are susceptible to aflatoxin contamination, a highly carcinogenic and potentially lethal mycotoxin. This work aimed to (1) identify novel lignocellulosic byproducts from the Sonoran Desert for use as substrate materials in Pleurotus ostreatus (oyster mushroom) cultivation; (2) evaluate the safety of mushrooms cultivated on plant products that are contaminated with aflatoxin; and (3) measure the amount of aflatoxin that is degraded by P. ostreatus after the contaminated products have been colonized by the fungus. Prosopis spp. pods were identified as suitable substrate component for P. ostreatus production by conducting yield evaluations and finding that the biological efficiency increased with increasing percentages of pods. No detectable quantity of aflatoxin could be measured in mushrooms that were cultivated on maize that was naturally contaminated with aflatoxin B1 at concentrations up to 2500 ng g⁻¹. P. ostreatus degraded AFB₁ by >85% in maize with initial concentrations of 2500 ng g⁻¹ AFB₁ in repeated experiments. Thus, the cultivation of P. ostreatus on aflatoxin-contaminated products may be a viable method to produce a safe and high quality food from an otherwise unsafe food source, and may double as a means to reduce the aflatoxin concentration in contaminated plant products to levels that are acceptable for use as livestock feed.

The area of secondarily salinized lands is increasing at a faster rate over time. Many irrigation districts around the world are shrinking as a result of secondarily salinized soils. This is resulting in crop yield losses. Irrigation practices with low drainage are intensifying this problem. Bioremediation of salinized soils with halophytes is one of the means of reversing this process. In these studies, we tested the growth and performance of four salt tolerant halophytes to varying levels of salinity. We analyzed the salt content of the plant tissues at different salinities, in order to determine how the plants' tissues reflect the increases in salinity. It was discovered that Allenrolfea occidentalis tolerates and grows well at higher salinities than the other plants tested. Furthermore, the concentration of salt in the aerial plant tissue was high and increased further in response to the external salt concentration. Halophytes such as A. occidentalis can be used to remediate abandoned salt affected lands and their biomass can have an added economic value. On the other hand, domestication of wild halophytes for agronomic purposes represents another opportunity to address the increasingly salinized soils and shortages of freshwater around the world. In these studies, we assessed the potential for improvement of an oilseed halophyte, Salicornia bigelovii, through selective breeding. We compared plant characteristics of S. bigelovii cultivars produced in breeding programs with wild germplasm in a green house common garden experiment. We concluded that S. bigelovii has sufficient genetic diversity among wild accessions and cultivars to support a crop improvement program to introduce desirable agronomic characteristics into this wild halophyte.

Site characterization methods for measuring the occurrence, magnitude, and rate of microbial mediated transformation processes were evaluated to assess the implementation of monitored natural attenuation (MNA) at chlorinated ethenes contaminated sites. A model site in Arizona, the Park-Euclid WQARF site in Tucson, was selected for the study. Field, geochemical, and compound specific carbon isotope fractionation (CSI) data confirm intrinsic biodegradation is occurring in the perched aquifer. Use of the BIOCHLOR model and a screening protocol support the potential for reductive dehalogenation found in the perched aquifer. Biotransformation of tetrachloroethene to cis-1,2-dichloroethene (cis-DCE) was achieved in microcosm studies. Transformation of cis-DCE to vinyl chloride and to ethene is, at the moment, the laboratory rate limiting step. PCR analysis established that the aquifer contains Dehalococcoides sp. and other dechlorinating microorganisms, though genes that encode for enzymes capable of achieving complete dehalogenation of the chlorinated contaminants were confirmed only in one monitoring well. The regional aquifer shows little evidence of intrinsic biodegradation. This study corroborates that CSI analysis can be used as an additional line of evidence to evaluate and verify MNA. Microbial analysis provides relevant information about the capabilities of native microbial communities to carry out reductive dehalogenation and thus, to naturally attenuate chlorinated compounds at a contaminated site. The combination of microcosm studies, CSI analysis, and bacterial DNA identification is becoming a convincing line of evidence for the assessment of MNA application to chloroethenes contaminated sites.

Bioremediacija suprantama kaip aplinką valanti technologija, kuri teršalų šalinimui naudoja biologinį potencialą. Apžvalgoje nagrinėjami įvairių polimerinių ir natūralios kilmės junginių biodegradacijos procesų ypatumai, mikrobiologinės grunto bioremediacijos efektyvumo priklausomybė nuo įvairių abiotinių ir biotinių veiksnių. Pateikta analizė apie žemiausios trofinės grandies-mikroorganizmų asociacijų formavimąsi ir funkcionavimą užterštame grunte, aptariamas bioaugmentacijos, biostimuliacijos, biopreparatų efektyvumas naftos produktais užteršto grunto bioremediacijai. Aptariamas naujas ištirtas termofilinių bakterijų naftaleno skaidymo kelias. Gautų duomenų pagrindu apžvalgoje daromos išvados, kad mikroorganizmai gali būti sėkmingai naudojami valant stipriai užterštą gruntą ex-situ sąlygomis. Bioremediacijos technologijos suteikia galimybes pagausinti vietines mikroorganizmų populiacijas, sustiprinti mikroorganizmų veiklą, naudojant papildomas maisto medžiagas, stimuliuoti aktyvių metabolitų sintezę. / Bioremediation is the application of biological processes for the clean up of pollutants present in the environment. The scope of the review encompasses the following subjects: biodegradation of various polymeric and natural origin compounds; the applications of microorganisms to laboratory scale and field scale soil bioremediation, with a focus on petroleum hydrocarbons; bioaugmentation and characterization of microbial communities; the factors affecting soil bioremediation processes including: availability of microbes, accessibility of contaminants, and a heterogeneous environment; the use of microbial metabolites, such as surfactants to improve availability of contaminants. From this review it can be concluded that microorganisms are an effective ex situ technology that can be used for bioremediation of problematic soils. Bioremediation technology allows for the convenient manipulation and control of several environmental parameters that could lead to enhanced and faster treatment of polluted soils: nutrient source (biostimulation), inocula (bioaugmentation), increased availability of pollutants by inducing biosurfactant production inside the microorganisms, etc. Bioremediation also encompasses ex situ methods like enzyme catalyzed pollutant breakdown. The data on the degradation of naphthalene by thermophilic bacteria via a novel pathway, through protocatechuate are presented.

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.

Weak organic acids and/or their salts were tested as soil washing or flushing agents for the ex- or in-situ remediation of soils polluted by heavy metals. Three soils naturally with heavy metals were used for the tea. / The three soils were characterized as a clay loam, loam and sandy clay loam. Their organic matter, pH, saturated hydraulic conductivity, cation exchange capacity, particle density and heavy metal contents were also characterized. The different retention forms of heavy metals in all 3 soils were studied by sequential extraction. The clay loam was contaminated with Cr, Hg, Mn and Pb while the loam and sandy clay loam were contaminated with Cd, Pb, Cu and Zn. Weak organic adds and/or their salts and chelating agents (EDTA and DTPA) were used at different pH, levels of concentration and leaching time in batch experiments to establish optimum conditions for maximum removal of heavy metals from the three soils. Citrate and tartarate were found to be quite effective, in leaching heavy metals from these soils. The rate of leaching of heavy metals from soils with citrate, tartarate and EDTA was modeled using two-reaction model at a constant pH and temperature. / Three contaminated soils of different textures were flushed in a column at optimum pH with a salt of weak organic acids, namely, citrate, tartarate, citrate+oxalate or a chelating agent such as EDTA and DTPA. The citrate and tartarate (ammonium salts) were found to be quite effective in removing heavy metals from the three contaminated soils while leaching little macronutrients and improving the soil's structure. An in-situ soil remediation simulation was also successfully tested using the sandy clay loam at large scale level in a tub (plastic container) using citrate as a flushing liquid. EDTA and DTPA were effective in removing the heavy metals except for Hg, but these strong chelating agents extracted important quantities of macronutrients from the soil. These chelating agents are also known to pollute the soil by being adsorbed on the soil particles. / A bioremediation process was developed using the fungus Aspergillus niger to produce weak organic acids (mainly citrate and partly oxalate depending on pH) for the leaching of heavy metals from contaminated soils. The fungus was cultivated on the surface of the three contaminated soils for 15 days at 30°C and a pH ≤ 4 to enhance the production of citric acid rather than oxalic acid which hinders Pb leaching. By extrapolating the result, the three contaminated soils were expected to be sufficiently remediated to meet the A category (Quebec clean up criteria for cleaning soils contaminated by heavy metals) after 20 to 25 days of leaching using this technique. / Finally, the leachate, collected following the soil remediation using weak organic acids and/or their salts, EDTA and DTPA was treated effectively using granular activated carbon.