Characterizing Hydrological Balance and Hydrochemistry of a Chronosequence of Newly Formed Wetlands within the Athabasca Oil Sands Region using Isotopic and Geochemical Tracers
Date
2023-09-06
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Abstract
Wetlands account for approximately 65% of the land area of the oil sands surface mining region, many of which have been lost due to resource extraction. Mined areas are reclaimed using saline-sodic materials present in both surficial geology and residual tailings, affecting wetlands constructed or naturally (“opportunistically”) forming within reclaimed landscapes. Newly-forming wetlands’ hydrological properties and ecological trajectories are poorly known. As part of the Boreal Wetland Reclamation Assessment Program, a chronosequence study design was used to infer the trends in water balance and geochemistry of 80 wetlands aged 2 to 40 years and varying in hydroperiod, salinity, and degree of riparian disturbance. Half of the wetlands were in reclamation landscapes of oil sands lease areas. The other half, located outside of the mining lease, which were considered ‘reference’ comparators. The region’s low-relief and wetland-dominated landscapes rendered traditional hydrological methods difficult to implement, so stable isotopes and geochemical tracers were used to infer the water balances. Isotope hydrological balances measured as Evaporation: Inputs ratio (E/I) varied significantly among wetlands on the two types of landscapes. Ratios for wetlands found on-lease were significantly higher (0.08-1.23) than those found off-lease (0.01- 0.46). Radon concentration (a proxy for groundwater inputs) in surface water of wetlands showed no significant difference between disturbance type and age. Analysis of hydrochemical facies revealed that NaCl and Mixed-water types dominated on-lease wetland waters, while in off-lease wetlands, Ca/MgHCO3 water type was dominant. Total dissolved solids concentrations were significantly higher in on-lease wetlands (2239 ± 1437 mg/L) than off-lease wetlands (766 ± 484 mg/L). ANCOVA analysis indicated that the largest effects on both TDS and Na:Ca ratios were landscape type and E/I(18O), while age played a less significant role. In contrast, Cl:HCO3 ratios were only influenced significantly by wetland age. Thus, surficial geology and evaporation effects seem to drive the large differences between wetlands found on and off lease; wetland age may play a role in decreased salinity found on and off the mining landscape. These findings may provide a useful comparative metric for reclamation success in landscapes possessing similar hydrological and hydrochemical facies.
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Keywords
Isotope hydrology, Newly formed wetlands, Reclamation, Radon
Citation
Wendlandt, M. E. (2023). Characterizing hydrological balance and hydrochemistry of a chronosequence of newly formed wetlands within the Athabasca oil sands region using isotopic and geochemical tracers (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.