Surface mining in the Athabasca oil sands region of Northern Alberta, Canada, results in the disturbance of significant areas of boreal forest landscape. The Aurora Soil Capping Study is a reclamation research project that aims to find the optimal soil capping (cover) material and thickness to re-establish a boreal forest ecosystem above a lean oil sands (LOS) disposal area at Syncrude's Aurora North mine. The objectives of this laboratory and field-based study are to (1) characterize the in-situ hydrocarbon composition of the LOS material, (2) determine the effect of temperature on rates of gas flux and the biodegradation potential of petroleum hydrocarbons (PHC) as a result of microbial activity and (3) determine the potential for PHC to leach into the groundwater system. The results of the laboratory-study show that temperature has a significant effect on the rate of PHC degradation as indicated by the linear relationship observed between temperature and CO2 gas flux rates. The respiratory results from the laboratory-based study were consistent and relatively comparable with data from the field study, which indicates that the column study could be useful in estimating in situ PHC degradation.

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In this field-scale study, air sparging (AS) system was applied at a petroleum-hydrocarbon spill site to remediate contaminated soil and groundwater in situ. The objective of this study was to evaluate the effectiveness of the AS system on volatile organic compounds (VOC) removal via the volatilization mechanism. Moreover, the AS system would also enhance the in situ bioremediation process due to the increased oxygen concentration in the subsurface. Results from the preliminary site characterization show that high concentrations of benzene and toluene were present in the subsurface in the western part of the site. Up to 15.62 and 30,957 mg/Kg of benzene and toluene were detected in soil samples, respectively. Moreover, up to 0.068 and 4.8 mg/L of benzene and toluene were observed in groundwater samples, respectively. The following remediation activities were conducted during the one-year investigation and remediation period: 1. Construction of four recovery wells were for light non-aqueous phase liquid (LNAPL) and contaminated groundwater extraction to prevent the expansion of VOC plume. The extracted groundwater was delivered to the wastewater treatment plant for treatment before discharge. 2. Installation of ten air sparging wells to enhance the removal of VOC through volatilization and biodegradation processes. 3. Conduction of (1) soil gas survey, (2) soil and groundwater sampling and analyses, and microbial enumeration periodically to evaluate the effectiveness of AS on VOC removal. Results from the field-scale study indicate that the AS system is able to effectively contain the plume. This can be confirmed by the following findings: (1) decrease in VOC concentrations in both soil and groundwater, (2) increase in carbon dioxide and increase in oxygen concentrations in the soil gas samples, and (3) increase in bacterial population in soil samples. Results from this study indicate that AS system can effectively contain the plume and manage this petroleum hydrocarbon spill site.

In this study, the biodegradation potential of MTBE in uncontaminated and previously contaminated aquifer sediments under aerobic conditions was investigated. Laboratory microcosms were constructed using aquifer samples collected from three different areas of a shallow gasoline-contaminated aquifer in eastern Fairfax Co., Va in the Atlantic Coastal Plain province. Uncontaminated aquifer samples were collected upgradient of the plume, and contaminated aquifer samples were collected in the source area and in an area downgradient of the source. Biodegradation of MTBE was observed in microcosms that contained previously contaminated aquifer sediments. More complete degradation was observed in aquifer sediments containing a low level of petroleum contamination than in heavily contaminated aquifer sediments. Biodegradation of MTBE appeared to be limited by a lack of oxygen in heavily contaminated soils. When degradation was discernible it appeared to follow a first order pattern with a rate constant (l) of between 0.037 and 0.066 d-1, following a lag period of 20 to 40 days. In microcosms containing lightly contaminated aquifer material, MTBE was respiked during active metabolism, and degradation occurred with no lag or acclimation period. Results indicated that little or no degradation occurred in the microcosms containing uncontaminated soil. The results of this research suggest that the availability and level of petroleum hydrocarbon compounds influence indigenous microorganisms capable of degrading MTBE. / Master of Science

Diesel #2 is used to heat nearly 400,000 dwellings in Virginia. Home heating oil released from leaking underground tanks located adjacent to homes and residing in unsaturated soil adjacent to houses poses a potentially serious health risk. Specifically, the migration of hazardous vapors into buildings, known as vapor intrusion, can negatively impact indoor air quality in homes and public buildings (USEPA 2015). In this look-back study, we assessed the potential for petroleum vapor intrusion by sampling soil vapor at 25 previously remediated spill sites. Residual contaminants, in particular total petroleum hydrocarbons (TPH) and naphthalene, were detected in approximately 1/3 of the samples. Concentration levels were correlated to site variables (building type, remediation time, physiographic region) including previous abatement measures. Spill category as assigned by the remediation contractor was investigated in conjunction with these three site variables. Remediation time was the most promising predictive site variable, with visible trends downward in DEQ Category 2 sites with increased remediation time. Higher contaminant concentrations were found near basement-style dwellings, which we hypothesize is due to the wall of the basement blocking horizontal migration of contaminants and the flow of oxygen to the release source zone. We found that many sites exceeded the sub-slab risk target threshold in naphthalene concentration, which has negative implications on previous abatement strategy efficacy. / Master of Science / Diesel is used to heat nearly 400,000 residences in Virginia. Diesel released from leaking underground tanks located adjacent to homes and residing in soil adjacent to houses poses a potentially serious health risk. Specifically, the migration of hazardous vapors into buildings can negatively impact indoor air quality in homes and public buildings (USEPA 2015). In this study, we assessed the potential for vapor migration by sampling soil vapor at 25 previously remediated spill sites. Residual contaminants were detected in approximately 1/3 of the samples. Concentration levels were compared to site variables (building type, time since spill, soil type) including previous remediation activity. Spill category as assigned by the remediation contractor was investigated in conjunction with these three site variables. Remediation time was the most promising as a predictive site variable. Higher contaminant concentrations were found near dwellings with basements, which we hypothesize is due to the wall of the basement blocking horizontal migration of vapors. We found that many sites exceeded the target threshold in naphthalene concentration, which has negative implications on previous remediation effectiveness.

Phytoremediation systems for petroleum hydrocarbons rely on a synergistic relationship between plants and their root-associated microbial communities. Plants exude organic compounds through their roots, which increase the density, diversity and activity of plant-associated microorganisms, which in turn degrade hydrocarbons. Understanding the mechanisms driving this relationship poses one of the more intriguing challenges in phytoremediation research. This study was designed to address that challenge. Plant-microbe interactions in a weathered-hydrocarbon contaminated soil were examined under controlled growth chamber, and field conditions. In both environments single-species grass treatments initially facilitated greater total petroleum hydrocarbon (TPH) degradation than <i> Medicago sativa </i> (alfalfa), mixed species, or control treatments. In growth chamber studies increased degradation was linked to increased aliphatic-hydrocarbon degrader populations within the rhizosphere. Under field conditions, specific recruitment of endophytic aliphatic-hydrocarbon degraders in response to high TPH levels may have facilitated increased degradation by the grass <i> Elymus angustus</i>(Altai wild rye, AWR). AWR stably maintained these communities during times of local drought, enabling them to act as subsequent source populations for rhizosphere communities. The broad phylogenetic diversity of AWR endophytes, compared to the <i> Pseudomonas</i>-dominated communities of other plants, contributed to the observed stability. The relative composition of exudates released by plants also impacted both degradation activity and potential. Alfalfa released higher concentrations of malonate, which hindered degradation by decreasing metabolic activity and concomitantly inhibiting catabolic plasmid transfer. In contrast, AWR exudates contained high levels of succinate, which was linked to increased catabolic gene expression and plasmid transfer. A reciprocal relationship between exudation patterns and endophytic community structure likely exists, and both parameters have a specific influence on rhizosphere degradation capacity. In this study, grasses were more successful in maintaining the specific balance of all parameters required for the transfer, preservation, and stimulation of hydrocarbon catabolic competency.

Phytoremediation systems for petroleum hydrocarbons rely on a synergistic relationship between plants and their root-associated microbial communities. Plants exude organic compounds through their roots, which increase the density, diversity and activity of plant-associated microorganisms, which in turn degrade hydrocarbons. Understanding the mechanisms driving this relationship poses one of the more intriguing challenges in phytoremediation research. This study was designed to address that challenge. Plant-microbe interactions in a weathered-hydrocarbon contaminated soil were examined under controlled growth chamber, and field conditions. In both environments single-species grass treatments initially facilitated greater total petroleum hydrocarbon (TPH) degradation than <i> Medicago sativa </i> (alfalfa), mixed species, or control treatments. In growth chamber studies increased degradation was linked to increased aliphatic-hydrocarbon degrader populations within the rhizosphere. Under field conditions, specific recruitment of endophytic aliphatic-hydrocarbon degraders in response to high TPH levels may have facilitated increased degradation by the grass <i> Elymus angustus</i>(Altai wild rye, AWR). AWR stably maintained these communities during times of local drought, enabling them to act as subsequent source populations for rhizosphere communities. The broad phylogenetic diversity of AWR endophytes, compared to the <i> Pseudomonas</i>-dominated communities of other plants, contributed to the observed stability. The relative composition of exudates released by plants also impacted both degradation activity and potential. Alfalfa released higher concentrations of malonate, which hindered degradation by decreasing metabolic activity and concomitantly inhibiting catabolic plasmid transfer. In contrast, AWR exudates contained high levels of succinate, which was linked to increased catabolic gene expression and plasmid transfer. A reciprocal relationship between exudation patterns and endophytic community structure likely exists, and both parameters have a specific influence on rhizosphere degradation capacity. In this study, grasses were more successful in maintaining the specific balance of all parameters required for the transfer, preservation, and stimulation of hydrocarbon catabolic competency.

Leaking of petroleum products from storage tanks is a commonly found cause of soil contamination. Among those petroleum products, diesel-oil contaminated soils are more difficult to treat compared to gasoline (a more volatile petroleum product). With the growing interest in environmental remediation, various approaches have been proposed for treating petroleum-hydrocarbon (PH) contaminated sites. Given that it is often not possible to remove the released oil or remediate the site completely within a short period of time, using the in situ remedial technology, soil excavation followed by more cost-effective technology should be applied to accelerate the efficiency of site cleanup. In the first-part of this study, laboratory degradation experiments were conducted to determine the optimal operational conditions to effectively and economically bioremediate diesel-fuel contaminated soils. In the second part of this study, a combined full-scale landfarming and biopile system was operated to cleanup diesel fuel-contaminated soils. In the laboratory study, except of frequent soil tilling for air replacement, different additives were added in the laboratory bioreactors to enhance the total petroleum hydrocarbon (TPH) removal efficiency. The additives included nutrients, TPH-degrading bacteria, activated sludge, fern chips, and kitchen waste composts. PH-degrading bacteria were isolated from PH-contaminated soils and activated sludge was collected from a wastewater treatment plant containing PH in the influent. PH-degrading bacteria and sludge were added to increase the microbial population and diversity. Fern chips and kitchen waste composts were added to increase the soil permeability. Results indicate that the bioreactor with kitchen waste compost addition had the highest TPH removal rate. The observed TPH-removal ratios for the compost, activated sludge, PH-degrading bacteria, fern chips, nutrients, TPH-degrading bacteria addition, and control (with HgCl2 addition) groups were 80.5%, 78.6%, 77.4%, 75.1%, 73.3%, 66.1%, and 1.6% respectively. In the field study, activated sludge was selected as the additive from the engineering point of view. With the addition of activated sludge, an increase of 20% was observed for TPH removal ratio. Results from the denaturing gradient gel electrophoresis (DGGE) tests show that the detected PH-degrading bacteria in the activated sludge included the following: Pseudomonas sp., Pseudoxanthomonas sp., Rhodocyclaceae bacterium, Variovorax sp., Acidovorax sp., Leptothrix sp., Alcaligenaceae bacterium, and Burkholderia sp. Some of these bacteria became dominant species in the field after a long-term operation, which was beneficial to the soil bioremediation. Results indicate that the in situ bioremediation has the potential to be developed into an environmentally and economically acceptable remediation technology.

Groundwater contamination by petroleum hydrocarbons has become one of the serious environmental problems in many countries. The sources of petroleum-hydrocarbon contaminants may be released from above ground and underground storage tanks, and pipelines. Petroleum hydrocarbons are mainly composed of benzene, toluene, ethyl- benzene, and xylems (BTEX), and other constituents such as methyl-tert-butyl ether (MTBE), naphthalene, 1,3,5-trimethylbenzene (1,3,5-TMB), and 1,2,4-trimethylbenzene (1,2,4-TMB). It is generally recognized that petroleum hydrocarbons have high risks to environmental receptors when hydrocarbon releases occur. Various biological, physical, and chemical remediation technologies (e.g. pump and treat, air sparging, enhanced bioremediation, and chemical oxidation) can be used to remediate petroleum-hydrocarbon contaminated groundwater. However, many of these techniques are typically costly or have limited applications. Permeable reactive barriers (PRBs) are a promising technology for the passive and in situ treatment of contaminated groundwater. A PRB can be defined as ¡§an emplacement of reactive materials in the subsurface designed to intercept a contaminant plume, provide a preferential flow path through the reactive media, and transform the contaminant(s) into environmentally acceptable forms to attain remediation concentration goals at points of compliance.¡¨ The oxygen release materials can be emplaced in the PRBs to passive increase dissolved oxygen (DO) in the subsurface to enhance the intrinsic biodegradation of dissolved hydrocarbons. In the first part of this study, guidelines for PRBs installation have been developed for the remediation of petroleum hydrocarbons, heavy metals, and organic solvents contaminated groundwater. PRB is a cost-effective approach for the remediation of contaminated aquifers. As contaminated groundwater moves through a permeable reactive barrier, the contaminants are scavenged or degraded, and uncontaminated groundwater emerges from the downgradient side of the reactive zone. The permeable reactive barrier concept has several advantages over other remediation technologies currently in use (e.g., pump and treat, air sparging), including absence of mechanical facilities and the electric power, no groundwater extraction and reinjection, treatment in situ, and cost-effective. The first part of this study presents the designs, applications, and case studies of PRB systems on groundwater remediation. In the second part of this study, oxygen release materials have been constructed and evaluated for the appropriate components in batch experiments. Microbial degradation of petroleum hydrocarbons in groundwater can occur naturally. Since the petroleum-hydrocarbons are generally degraded faster under aerobic conditions, aerobic bioremediation can be applied to enhance the biodegradation of petroleum-hydrocarbons within of the plume if oxygen can be provided to the subsurface economically. Batch experiments were conducted to design and identify the components of the oxygen-releasing materials. Cement and gypsum were used as a binder in this mixtures experments. (1) using cement as the binding material The mixtures of the oxygen release material were prepared by blending cement, peat, sand, ethylene-vinyl acetate copolymer(EVA), calcium peroxide (CaO2), and water together at a ratio of 1.0¡G0.18¡G0.20¡G0.10¡G1.12¡G1.74 by weight. Cement was used as a binder and regular medium filter sand was used to increase the permeability of the mixture. Calcium peroxide releases oxygen upon contact water. The designed material with a density of 1.9 g/cm3 was made of 3.5 cm cube for the batch experiment. Results show that the oxygen release rate of the material is 0.046 mg O2/day/g rock. The oxygen release material was able to remain active in oxygen release for more than three months. (2) using gypsum as the binding material The mixtures of the oxygen release material were prepared by blending gypsum, CaO2, sand, and water together at a ratio of 1¡G0.5¡G0.14¡G0.75 by weight. Gypsum was used as a binder and regular medium filter sand was used to increase the permeability of the mixture. Calcium peroxide releases oxygen upon contact water. The designed material with a density of 1.1 g/cm3 was made of 3.5 cm cube for the batch experiment. Results show that the oxygen release rate of the material is 0.031 mg/day/g. The oxygen release material was able to remain active in oxygen release for more than three months. In the third part of this study, immobilization technology was applied to produce the low permeability wrapping film for the construction of oxygen-releasing granular materials. The mixtures of the oxygen release material were prepared by blending alginate, CaO2, and sand together at a ratio of 8.3¡G1.0¡G1 by weight. The low permeability wrapping film of the oxygen release material was able to remain active in oxygen release for two months. In the fourth part of this study, a laboratory-scale column experiment was conducted to evaluate the feasibility of this proposed system on the bioremediation of petroleum-hydrocarbon contaminated groundwater. This system was performed using a series of continuous-flow glass columns including four consecutive soil columns. Simulated petroleum-hydrocarbons contaminated groundwater with a flow rate of 0.263 m/day was pumped into this system. In the column experiment, the samples of column influent and specified sampling ports were collected and analyzed for pH, DO, BTEX, MTBE, and microbial populations. Results show that up to 99% of BTEX removal was observed in this passive system. Results from this study would be useful in designing an efficient and cost-effective passive oxygen-releasing and bioremediation system to remediate petroleum- hydrocarbon contaminated aquifer.