Assessment the pools and potential redistribution of sodium in a constructed fen peatland system

English Abstract:

A constructed fen peatland on a post-mined oil sands landscape in northern Alberta incorporates materials from the mining site into the constructed system. Peat is used for the fen, tailings sand is used for the upland and petroleum coke is used for a high permeability connecting basal layer. The use of these byproducts of oil production requires an understanding of the transport and attenuation mechanisms of potential solutes they may contain such as sodium (Na), since they may impact the plants and microbial community of the fen. To meet this goal we need a prior understanding of the type of solutes, their concentration and movement. We believe sodium (Na) to have the highest potential toxicity to plants. Material digestion results indicate that following construction peat contained the highest concentration of Na (445 mg/kg) compared with coke (215 mg/kg) and sand (80 mg/kg). However, results of a batch experiment showed that peat has the lowest range of available Na of the building materials examined. Using the results a mass balance of Na was done and the calculations indicate that a large pool of available Na exists in the created upland. This pool, which through groundwater flow is directed to the peatland, exceeds the adsorption capacity of the peat. If the outflow of Na in surface runoff from the fen is limited, as is expected, Na is likely to accumulate in the fen over the short- and medium-term, with implications for vegetation succession.