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HUMIC SUBSTANCES AS SOIL AMENDMENTS IN COAL MINE RECLAMATION

  • Author / Creator
    Yihan Zhao
  • Coal is mined for energy generation around the world, resulting in extensive disturbances to soil health and vegetation, and producing large amounts of waste. Heavy metals enter the environment through coal industry activities before being transmitted to the food chain. Reclaiming post mining sites covered by sandy soils with low nutrient and high heavy metal concentrations for agricultural uses is very challenging. Using coal waste derived humic substances as soil amendments may enhance soil reclamation outcomes due to their great potential as a soil conditioner, plant growth biostimulator, and heavy metal adsorbent.
    This research was undertaken in three greenhouse and laboratory experiments at the University of Alberta that ran for three months each, and two field experiments on a former underground coal mine (Shendong mining area) in China that ran for two years. The overall objective was to assess potential of a coal waste derived humic substance product called nano humus as a soil amendment for mined sandy soils in combination with other materials.
    Direct application of nano humus at the beginning of each growing season at 150 g/m2 was a suitable reclamation strategy. The beneficial effect of nano humus was expressed in year two in the field. As a soil conditioner, nano humus positively changed most soil variables, particularly soil cation exchange capacity (38 %), total organic carbon (49 %), and available nitrogen, phosphorus, and potassium (29 to 64 %). As a plant growth biostimulator, nano humus significantly enhanced the total biomass of alfalfa (Medicago ruthenica L.) by 749 %, barley (Hordeum vulgare L.) by 250 %, and sea buckthorn (Fructus Hippophae L.) by 147 %. As a heavy metal adsorbent, nano humus removed 89 % of cadmium from contaminated water after 15 minutes and 93 % after 24 hours at a high metal concentration of 100 mg/L; it reduced 25 % of thallium, 18 % of cadmium, and 3 % of arsenic from contaminated soils after two years. Beneficial effects were more pronounced with combined fertilizer and arbuscular mycorrhizal fungi than with sole applications of each.
    Our findings confirmed the great application potential of a lignite derived humic substance as a plant growth stimulator, soil conditioner, and heavy metal adsorbent in coal mine reclamation and remediation. The pronounced performance of combined applications with arbuscular mycorrhizal fungi and fertilizer provided insights for future reclamation strategies. Our research has global implications as it can be applied in other sandy soil regions facing similar reclamation challenges in the world where industrial released heavy metals pose a great risk to the environment and public health substantially.

  • Subjects / Keywords
  • Graduation date
    Spring 2022
  • Type of Item
    Thesis
  • Degree
    Doctor of Philosophy
  • DOI
    https://doi.org/10.7939/r3-fpzk-sp93
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.