EFFECTS OF PETROLEUM HYDROCARBON CONCENTRATION AND BULK DENSITY ON THE HYDRAULIC PROPERTIES OF LEAN OIL SAND OVERBURDEN AND WATER STORAGE IN OVERLYING SOILS

Coarse textured soils with low water and nutrient retention are commonly the only available materials for reclamation of the projected 480,000 hectares of disturbed land in the Alberta oil sands. It is important to understand the processes in the soils being used for reclamation to be able to re-create conditions that occurred prior to disturbance. Extensive research has been conducted to understand the hydraulic processes in mineral soils, however much of the soils that are used for reclamation in the Alberta oil sands are impregnated with petroleum hydrocarbons (PHCs). Little is known of the effects of PHCs on soil hydraulic properties. Lean oil sand (LOS) is an overburden material that contains PHCs, and is considered mine waste. LOS must be reclaimed, and is currently being tested as the base soil layer for some of the reclamation being conducted in the Alberta oil sands. It is important to understand how the hydraulic properties in the LOS as well as in the overlying reclamation soils will be affected by PHCs. The main objective of this thesis is to determine the efficacy of using LOS as a base soil layer on the successful reclamation of disturbed land in the Alberta oil sands. This was done by: 1) Evaluating how PHCs and bulk density influence the hydraulic properties of LOS and 2) Determining how the soil hydraulic properties in the layers overlying the LOS are affected by the heterogeneity of PHC concentration and bulk density of the LOS. Soil cores were packed with LOS with varying PHC concentrations and bulk densities to test water retention curves and saturated hydraulic conductivity of the LOS. Soil columns were packed with a base LOS layer and reclamation cover soils that are used in the Alberta oil sands. The soil columns were used to test water and nutrient dynamics in the reclamation soil profile. It was found that both bulk density and PHC concentration had an effect on the hydraulic properties in LOS as well as in the overlying reclamation profile. The porosity of soil is largely affected by bulk density, so as bulk density of the LOS increased, it lead to lower water retention at saturation, but higher water retention at soil suctions associated with field capacity and permanent wilting point (PWP). This led to LOS at higher bulk densities having higher available water holding capacity (AWHC) and lower Ks, providing the overlying soil profile with more water and nutrients for a longer time for plants to access. Furthermore, PHCs reduced water retention in LOS due to plugging mainly the soil micropores pores and connecting porosity. This lead to lower Ks of the LOS, which resulted in an increased water and nutrient retention in the overlying soil profile. Results show that the use of LOS in the reclamation of coarse textured soils in the Alberta oil sands can aid in creating suitable soil conditions leading to reclamation success

The Impact of LFH Mineral Mix on the Function of Reclaimed Landscapes in the Athabasca Oil Sands Region, Alberta, Canada

The Athabasca Oil Sands Region (AOSR), located within the Western Boreal Plains (WBP) is characterized by a mosaic of boreal uplands and peatlands that dominate the terrain. These landscapes are underlain by oil-bearing formations (bituminous sands) and are disturbed or completely removed during resource exploration and extraction. Oil companies operating in the AOSR are mandated by the Government of Alberta to return their leased lands to an equivalent land capability. In doing so, new landscapes are constructed using materials salvaged from the pre-mined landscape and by-products from the mining process itself. Successful reclamation rests on an understanding of the soil physical properties that characterize these materials and how they impact intended function, both at the time of placement and in later years of reclamation. This research specifically focuses on the use of LFH mineral mix (hereafter referred to as LFH) as a cover soil in reclaimed landscapes and how its properties impact functionality. The temporal evolution of LFH was assessed using six reclamation study sites of six distinct ages (4 years post reclamation – 11 years post reclamation). A series of soil physical properties were analyzed in the top 10 cm of the LFH profile and while certain properties did follow a trend with time, other properties were likely an intrinsic property of the LFH upon placement. The dynamic nature of LFH captured within the time frame of this study contributes to an improvement in hydrological response with time (increasing α and maximum infiltration rates). Properties such as soil organic matter and bulk density, that would less readily change under biotic and abiotic forces impact the initial quality of LFH upon placement. And, while higher initial quality does improve the likelihood of success in early years of reclamation, sites of lower initial quality still performed as intended. Considering the entire soil profile, LFH over subsoil (glacial till or tailings sand) is likely to form a percolation barrier. The presence of these barriers (hydraulic or capillary) can be detected using easily obtained soil physical properties and they should be considered along with the intended function of a reclaimed landscape. Both types of barriers can benefit vegetation as water is held above the interface of the two materials, increasing field capacity and thus available water holding capacity. However, their behaviour in relation to increasing soil moisture conditions differs. While a hydraulic barrier is weakened, allowing more water to steadily move beyond the interface, a capillary barrier is broken through, and the two materials remain hydraulically connected until the barrier is restored. The behaviour of a capillary barrier could benefit landscapes where percolation into the subsurface is crucial to success

Contaminant migration of oil-and-gas drilling fluids within the glaciated sediments of north-central North Dakota

A common practice during oil and gas well-site reclamation in North Dakota is to bury the drilling muds in shallow trenches near the borehole. These muds are saltwater based (between 100,000 and 300,000 mg/L of NaCl) and can contain high concentrations of chromium, lead, and other. toxic trace metals. Two reclaimed oil and gas well sites were chosen for study in north-central North Dakota: the Winderl site in southeastern Renville County, and the Fossum site in west-central Bottineau County. The Winderl oil well was drilled in 1959, and the drilling fluids were disposed of in a shallow pit excavated in Pleistocene glaciofluvial deposits. The Fossum oil well was drilled in 1978 and the drilling fluids were disposed of in trenches excavated in Pleistocene till. A total of 41 shallow piezometers (maximum depth is 62 feet {18.9 m)) and 13 pressure-vacuum lysimeters were installed in and around the two disposal sites to obtain groundwater and pore-water samples. Vertical electrode sounding resistivity profiles were conducted at both sites utilizing 14 electrode spacings down to a depth of 100 feet (30.5 m). Sediment samples were obtained with Shelby tubes for x-ray fluorescence and x-ray diffraction analyses. Additional chemical analyses were performed on saturated-paste extracts from the Shelby-tube samples. The results of chemical analyses of pore water, groundwater, saturated-paste extracts, and the earth resistivity surveys indicate that leachate is being generated from buried drilling fluid at both study sites. At the Winderl site, contaminants have migrated beyond 400 feet (122 m), the extent of the monitored area, which has resulted in degradation of the Spring Coulee Creek Aquifer. A one-dimensional analytical solute transport equation was utilized to illustrate the potential for contaminant migration at the site. The equation predicts high concentration of contaminants over 3300 feet (1000 m) from the source area. Contaminant migration within the till at the Fossum site is believed to occur along fractures directly below the water table. The estimated groundwater velocity through these fractures is 3.8 m/day {12.8 ft/day) compared to 7.2 x 10-7 (2.4 x 10-6 ft/day) estimated for the till matrix. However, it has been reported that molecular diffusion is an important retardation mechanism that reduces the concentration of contaminants along these fractures with distance from the source. Also, the fractures constitute a small volume of pore space; ·therefore, the quantity {or flux) of water flowing along the fractures is small. Disposal of drilling fluids in glaciofluvial sediments is not recommended. The study at the Winderl site is evidence of the adverse environmental impact such disposal can lead to. The impact of drilling fluid disposal in till is dependent upon the geologic setting. Migration of the drilling fluid constituents will occur along fractures in the till; widespread contamination could result if these contaminants intersect penneable lenses. A subsurface investigation is necessary at the disposal sites in till to identify these permeable lenses and to determine if any nearby aquifers exist

COLLOID MEDIATED TRANSPORT OF HEAVY METALS IN SOILS FOLLOWING RECLAMATION WITH AND WITHOUT BIOSOLID APPLICATION

Soils disturbed by strip mining practices may have increased colloid loads moving to groundwater resources, also enhancing the transport of contaminants into our water resources. We hypothesize that contaminant transport within soils following mining is enhanced by colloid mobility. Two sites were chosen for this study, a 30-year old reclaimed strip mine in southwest Virginia and a recently mined area from eastern Kentucky. Intact reclaimed soil monoliths were retrieved from sandstone derived soils in southwestern Virginia. Reclaimed monoliths from eastern Kentucky were recreated in the lab. Intact undisturbed (native) soil monoliths representing the soils before mining were also sampled for comparison. Biosolids were added to an additional reclaimed monolith at a rate of 20 T/acre. Leaching experiments with deionized water at a rate of 1.0 cm/h involved 6 cycles of 8 hours each, giving each monolith at least 2 pore volumes of leaching. Native soil monoliths from Virginia had an average colloid elution of 857 mg over all cycles, reclaimed soil monoliths had an elution of 1460 mg, reclaimed soil monoliths with spoil material had a colloid elution of 76 mg, and when biosolids were amended to reclaimed soil and spoil monoliths, 870 mg colloids were eluted. Native soil monoliths from eastern Kentucky eluted 7269 mg colloids, reclaimed monoliths from eastern Kentucky eluted 10,935 mg colloids, and reclaimed soils with spoil material eluted no colloids. Lime stabilized biosolids enhanced colloid elution due to high pH dispersing material within the monoliths, while spoil materials with high density and salt content reduced colloid elution. Metal loads in solution were mobilized by DOC, particularly in low sulfate environments, while colloid bound metals increased the total metal loads in the order of Pb \u3e Ni \u3e Cu \u3e Cd \u3e Zn \u3e Cr

Evaluation of Preferential Flow Processes in Reclamation Soil Covers

To predict the effectiveness of land reclamation, it is important to understand how water and solutes are transported within reconstructed landscapes. The objective of this study was to examine the influence of preferential flow on salt leaching in reclamation soil covers. The study site was a reconstructed landscape where saline-sodic minespoil from oil sands mining was capped with layers of glacial and peat mix soil. Preferential flow was investigated using laboratory column experiments and in situ adsorptive dye and conservative tracer experiments. Results from column experiments and dye tracer experiments indicate that preferential flow is an important and prevalent mechanism of solute transport. Column experiments, which used time-domain reflectometry to monitor the transport of a chloride tracer through an undisturbed core of peat mix soil, determined immobile water fractions (èim/è) ranging from 80-99% and diffusive mass transfer rates (á) between 0.15 - 2.0 h-1. Breakthrough curves showed the early arrival of chloride and extended tailing. Dye tracer experiments, in which Brilliant Blue dye was applied in solution to the soil surface, were carried out at 6 hillslopes plots. Approximately 24 hours after dye application, a vertical soil face was excavated to reveal stained flow patterns. Preferential flow as macropore flow, fingering, and / or funneling was observed at each plot. Results from the conservative tracer field study indicated soil solutes were flushed by a combination of vertical and lateral flow processes. A large pulse of bromide and chloride was applied across the lower slope of the 0.35-m cover. Soil sampling at approximately 1 and 2 years later determined vertical leaching, lateral translocation downslope, and upwards movement of soil solutes. Matrix flow during the spring melt, combined with matrix flow and / or preferential flow during summer and fall periods, was responsible for the vertical leaching of solutes. Subsurface flow generated in response to the spring melt or due to differences in soil hydraulic conductivity was responsible for the lateral transport of solutes. As a result of advective or diffusive processes, solutes were transported upwards into the overlying soil. These results suggested that despite the existence of preferential flow, there were other mechanisms of solute transport which served to leach and flush salts from the soil

Impact of Soil Properties on Removal of Emerging Contaminants from Wastewater Effluent During Soil Aquifer Treatment

This study evaluates soil properties that impact the effectiveness of soil aquifer treatment (SAT) as a polishing step to the remove two classes of ECs from wastewater effluent: pharmaceuticals and personal care products (PPCPs), and engineering nanomaterials (ENMs). In recent years, it has been determined that elevated levels of emerging contaminants (ECs) are being released into the environment with wastewater effluent. ECs are proven to cause adverse environmental and health effects as a result of long-term exposure. It is important to evaluate sustainable solutions to improve the current methods of wastewater treatment to address these ECs. Soil aquifer treatment (SAT) is a sustainable, cost effect treatment alternative to advanced treatment at a wastewater treatment plant. SAT replenishes local groundwater supplies while allowing for indirect potable reuse, if contaminants of concern such as ECs can be effectively removed from the water. Since wastewater effluent can contain a variety of contaminants with myriad physical and chemical properties, understanding the potential of the aquifer itself to provide EC removal is a key step in establishing SAT as a viable treatment alternative. Peer-reviewed research studies were analyzed to determine the soil properties that affect the fate and transport of ECs in the aquifer environment. The data was complied to produce recommendations for an effective SAT site. Physical and chemical properties of the soil facilitate contaminant removal as the groundwater flows through the aquifer. This study determined that removal of ECs from effluent had a correlation with (1) high clay content, (2) small Darcy Velocity, (3) high soil organic matter content, and (4) low sand content. Based on the 6 peer-reviewed research studies reviewed, the removal of nanomaterials is affected by clay content and sand content, but not soil organic matter content. Conversely, the removal of PPCPs is affected by clay content and soil organic mater content, but not sand content. It can be concluded that two different removal mechanisms facilitate the removal of nanomaterials versus PPCPs; physical removal for nanomaterials and chemical removal (sorption) for PPCPs. Clay facilitates the removal of both contaminants. The small soil diameter of clay forms smaller pores in the soil media. This causes increased pore straining, while also restricting the flow through the soil, which increases the contact time between the soil particle and the ECs. Additionally, clay has a large surface area, which increases surface interactions, such as sorption, of the EC to the surface of the clay particle

Long-term phosphorus removal in land treatment systems: Evaluation, experiences, and opportunities

Excessive release of phosphorus (P) from urban wastewater into water bodies is a significant environmental concern. Land treatment systems (LTS) have been used for the last 150 years as a low-cost and low-energy tertiary wastewater treatment. However, their P removal capacity is limited by soil adsorption capacity. Accurate P-removal lifespan prediction is needed to provide confidence in this technology and to support long-term wastewater treatment planning. This review outlines the history of LTS, describes the main P removal processes in soils, and critically analyzes the research methods used to date to assess long-term P removal in soil. Finally, an assessment is made of the role that modeling tools can play in aiding our understanding of P processes in LTS soils and in forecasting system longevity

Fate and transport of chromium in industrial sites: dynamic simulation on soil profile

Direct discharge of chromium-containing waste water and improper disposal of waste residues in industrial sites may lead to the vertical migration of metals into aquifers, posing serious threat to soil-groundwater system. The heterogeneity in soil profile further aggravates the complexity and unpredictability of this transport process. However, topsoil was the main focus of most studies. Herein, the vertical transport and transformation of Cr in soils at different depths in three industrial sites (i.e., Shijiazhuang, Zhuzhou, and Guangzhou) were investigated to delineate Cr transport and retention characteristics under complex conditions. Regional and vertical differences in soil properties led to the specificity in Cr migration behaviors among these three sites. Correlation analysis showed that soil pH (r = −0.909, p r = 0.949, p 3 within 20 years. Heavier rainfall condition exacerbated the contamination due to an increased pollutant flux and enhanced convection. Specially, Cr was fixed in the topsoil of Zhuzhou site with the formation of PbCrO4 and presented least vertical migration risk. The conclusions above can provide scientific theoretical guidance for heavy metal pollution prevention and control in industrial contaminated regions.Environmental Biolog