Atmospheric deposition of nitrogen, sulfur and base cations in jack pine stands in the Athabasca Oil Sands Region, Alberta, Canada.

Abstract Atmospheric deposition in the Athabasca Oil Sands Region decreased exponentially with distance from the industrial center. Throughfall deposition (kg ha −1  yr −1 ) of NH 4 –N (.8–14.7) was double that of NO 3 –N (.3–6.7), while SO 4 –S ranged from 2.5 to 23.7. Gaseous pollutants (NO 2 , HNO 3 , NH 3 , SO 2 ) are important drivers of atmospheric deposition but weak correlations between gaseous pollutants and deposition suggest that particulate deposition is also important. The deposition (eq ha −1 ) of base cations (Ca + Mg + Na) across the sampling network was highly similar to N + S deposition, suggesting that acidic deposition is neutralized by base cation deposition and that eutrophication impacts from excess N may be of greater concern than acidification. Emissions from a large forest fire in summer 2011 were most prominently reflected in increased concentrations of HNO 3 and throughfall deposition of SO 4 –S at some sites. Deposition of NO 3 –N also increased as did NH 4 –N deposition to a lesser degree.