Physical Properties of Tar Sand Tailings that Influence Their Ability to Sustain Plant Growth

• Main Author: Cole, Timothy
• Format: Others
• Published: TopSCHOLAR® 1985
• Subjects: Western Kentucky University; Conservation; Agriculture; Earth Sciences; Environmental Sciences; Life Sciences; Natural Resource Economics; Natural Resources Management and Policy; Physical Sciences and Mathematics; Soil Science
• Online Access: http://digitalcommons.wku.edu/theses/1900; http://digitalcommons.wku.edu/cgi/viewcontent.cgi?article=2903&context=theses

The mining of bituminous sandstone rock for the purpose of extracting bitumen has created a need for reclamation. One such mine is located in northern Logan County. Their mining operation involves removing large sections of sandstone, which is impregnated with bitumen, and crushing it to sand-sized material. The sand-sized material is then mixed with organic solvents which extract the bitumen. Once separated, the bitumen is stored for future refinement and the spent sand is stockpiled for later disposal. The spent sands or waste material are referred to as tar sand tailings. These tailings have particular properties which make reclamation efforts difficult. One restrictive property is the 30 percent swell factor, which prevents replacement of the tailings into their respective mined area. Another property is the tailings’ hydrophobicity. This water repellence prevents merely spreading the tailings onto the surface. Experiments were conducted at Western Kentucky University during 1984 and 1985 to determine methods to lessen the hydrophobic tendencies and allow for reclamation. These experiments included mixing the tailings with the existing soil and adding surfactants to the tailings. Water holding capacities, infiltration rates, and the ability to sustain plant life were determined and evaluated. It appears that the residual bitumen not removed by the extraction process causes the hydrophobic tendencies of the tailings. This conclusion was based on a comparison of pure tailings and tailings which were subjected to 500°C temperatures for 24 hours which could destroy all organic material, specifically the residual bitumen. The pure tar sand tailing held 0.44 percent moisture and the tailings with the organic material removed held 27.48 percent moisture. Mixtures of tailings and Zanesville soil were also evaluated and compared to the tailings with and without organic material. The percent moisture of the soil was not significantly different from the tailings without organic material. All mixtures were significantly lower than the soil or the tailings without organic material and significantly higher than the pure tar and tailings. However, the mixtures apparently can hold sufficient moisture for plant growth. Water infiltration rates through various mixtures of tailings and soil with and without surfactants were also evaluated. It was concluded that a tailings/soil mixture of 75/25 percent with and without surfactant and 90/10 percent mixture with surfactant allowed the fastest water infiltration. The rate of infiltration is important since the Logan County topography is favorable for runoff erosion. Rye (secale cereale) was grown in various mixtures of tailings and soil with and without surfactants to determine phytotoxic effects. Visual observations of the growing plants indicated no phytotoxic effects due to the bitumen or surfactants. However, dry matter yields of the plants differed significantly. The lower yield of some plants could be attributed to a lack of moisture since the lowest yields were in the pure tailings with and without surfactant. In conclusion, the results of this study revealed that tar sand tailings do have hydrophobic tendencies apparently due to residual bitumen. These tendencies can be buffered by mixing the waste material with an existing soil or by complete combustion of the residual organic material. Also it was concluded that vegetation could be established on the mixtures of tailings and soil and thus, the land reclaimed.