Can Plant or Lichen Natural Abundance 15N Ratios Indicate the Influence of Oil Sands N Emissions on Bogs?

Kelman Wieder
Melanie Vile
Dale Vitt
Kimberli Scott
Bin Xu
James Quinn
Cara Albright
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The 140,329 km2 Athabasca Oil Sands Administrative Area (OSAA), which contains
8982 km2 of bogs. Since the late 1970s, N emissions from oil sands development in the OSAA have steadily increased, reaching over 80,000 metric tonnes yr-1 in 2017.
If oil sands N emissions have distinct stable isotopic signatures, it may be possible to
quantify the extent to which these emissions have affected N cycling in surrounding aquatic, wetland, and terrestrial ecosystems. To assess the potential for 15N as a tracer of oil sands N emissions, we measured natural abundance 15N ratios and tissue N concentrations in 10 plant or lichen species at 6 peatland sites at different distances from the oil sands region, collected on 17 sampling dates over three years (2009–2011).
New hydrological insights: To understand how the pressures of changing N and S deposition regimes and hydrologic disturbance interactively affect the region’s wetlands, it is critical to understand how these pressures act individually. The epiphytic lichen, Evernia mesomorpha, was the only species that exhibited patterns that could be interpreted as being influenced by oil sands N emissions. The paucity of data on δ15N signatures of oil sands related N sources precludes definitive interpretations of δ15N in plant or lichen tissues with respect to oil sands N emissions.