Is bog water chemistry affected by increasing N and S deposition from oil sands development in Northern Alberta, Canada?

Abstract

Nitrogen and sulfur emissions from oil sands operations in northern Alberta, Canada have resulted in increasing deposition of N and S to the region’s ecosystems. To assess whether a changing N and S deposition regime affects bog porewater chemistry, we sampled bog porewater at sites at different distances from the oil sands industrial center from 2009 to 2012 (10-cm intervals to a depth of 1 m) and from 2009 to 2019 (top of the bog water table only). We hypothesized that: (1) as atmospheric N and S deposition increases with increasing proximity to the oil sands industrial center, surface porewater concentrations of NH 4 + , NO 3 − , DON, and SO 4 2− would increase and (2) with increasing N and S deposition, elevated porewater concentrations of NH 4 + , NO 3 − , DON, and SO 4 2− would be manifested increasingly deeper into the peat profile. We found weak evidence that oil sands N and S emissions affect bog porewater NH 4 + -N, NO 3 − -N, or DON concentrations. We found mixed evidence that increasing SO 4 2− deposition results in increasing porewater SO 4 2− concentrations. Current SO 4 2− deposition, especially at bogs closest to the oil sands industrial center, likely exceeds the ability of the Sphagnum moss layer to retain S through net primary production, such that atmospherically deposited SO 4 2− infiltrates downward into the peat column. Increasing porewater SO 4 2− availability may stimulate dissimilatory sulfate reduction and/or inhibit CH 4 production, potentially affecting carbon cycling and gaseous fluxes in these bogs.

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