Preliminary assessment of greenhouse gas emissions from a constructed fen on post-mining landscape in the Athabasca oil sands region, Alberta, Canada

The ongoing reclamation of boreal forest areas that are impacted by oil sands mining involves the construction of wetlands as desirable land uses. Constructed wetlands receiving peat-mining runoff are known to be major sources of greenhouse gas (GHG) emissions to the atmosphere. However, the GHG fluxes of a fen that is constructed with drained peat substrate and receives runoff containing effluents of salt and naphthenic acids is not known. Using a fen constructed in the post-mining landscape of the Athabasca oil sands region, a study was conducted to quantify the fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) during the peak growing seasons over the first two years following revegetation. The specific objective of this study was to evaluate the effect of revegetation strategies and other environmental characteristics on the fen GHG emissions over the growing season. Relative to a natural fen, our results show significantly lower fluxes of CH4 (p < 0.001), which correlate with higher bulk density, lower organic matter content, and higher pH and SO42− concentration in the constructed fen. Revegetation did not stimulate CH4 production, but increased CO2 uptake and reduced N2O emissions relative to the non-vegetated control. These results suggest that revegetation strategies and water chemistry might be more important controls on GHG fluxes than substrate quality in a constructed fen. Although the current edaphic conditions in the constructed fen support the potential for a net uptake of GHGs over the growing season, additional monitoring is required to evaluate if these conditions will persist in the long-term. We recommend that future reclamation projects should consider the potential effects of construction materials on water chemistry prior to use in fen reclamation.