Name
Spatial patterns and mass balance of sodium in near-surface peat of a constructed fen
Description
At the Nikanotee Fen Watershed, a pilot reclamation project in the Athabasca Oil Sands Region, Alberta, elevated sodium (Na+) in the porewater of mine-waste materials has been revealed to migrate to the fen through groundwater, likely affecting fen vegetation health and steering the ecological development of the fen. The goal of this research is to quantify the spatial distribution of Na+ and to characterize the Na+ mass balance of the surface and shallow subsurface of the fen. In general, the highest Na+ concentrations were found in the wettest part of the fen in the southwestern corner, and the lowest in the relatively dry northeast corner near the drainage outlet. Na+ concentrations in ponded surface water were responsive to rainfall-induced dilution and evapoconcentration, whereas porewater salinity in shallow groundwater was insensitive to meteorological conditions. Given the relatively small proportion of the Na+ mass outflow (average rate of 4 kg day−1 between June and August) controlled by surface discharge annually, and the greater rate of mass inflow relative to export, elevated salinity will likely be sustained for several decades. Since elevated Na+ concentrations are impacting the rooting zone of vegetation and have exceeded the salinity stress-threshold of mosses, targeting salt-tolerant vegetation will be important to maintain carbon accumulation in constructed systems.