Atmospheric deposition of sulfur and inorganic nitrogen in the Southern Canadian Rocky Mountains from seasonal snowpacks and bulk summer precipitation Vivian Wasiuta a,⇑ , Melissa J. Lafrenière a , Ann-Lise Norman b,c a Department of Geography, Queen’s University, Mackintosh-Corry Hall, Room D201, Kingston, ON K7L 3N6, Canada b Department of Physics and Astronomy, 834 Campus Place N.W, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada c BSc Environmental Science Program, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada article info Article history: Received 12 November 2013 Received in revised form 7 January 2015 Accepted 30 January 2015 Available online 7 February 2015 This manuscript was handled by Laurent Charlet, Editor-in-Chief, with the assistance of M. Todd Walter, Associate Editor Keywords: Nitrogen Sulfate Atmospheric deposition Precipitation Critical loads Rocky Mountains summary This study quantified atmospheric deposition of sulfur (S) and nitrogen (N) in the alpine of the Southern Canadian Rocky Mountains and evaluated loads relative to critical limits for ecologic effects on alpine ecosystems from N saturation and acidification. Deposition was evaluated by collecting seasonal snow- pack and summer bulk precipitation samples along elevational transects in the alpine Haig Valley and given regional context using snowpack samples from six additional glacier sites. S and N deposition were evaluated in terms of two conceptual models. Model 1 representing deposition from emissions that are mainly distant and Model 2 representing deposition from a mixture of distant and local to regional emis- sions. Annual S and N (including ammonium (NH 4 + ), nitrate (NO 3  ) and nitrite (NO 2  )) deposition in the alpine Haig Valley was 0.74 ± 0.18 kg S ha 1 and 1.10 ± 0.18 kg N ha 1 yr 1 , which is sufficiently high for the occurrence of detrimental ecologic effects related to N saturation in the most sensitive alpine eco- systems, but lower than the critical limit for acidification. Snowpack S and N deposition was consistent with well mixed air mainly from distant sources (Model 1), therefore indicating S and N were largely transported within the precipitating air mass and or picked up by the air mass in transit to the alpine Haig Valley. Relatively consistent deposition of S and N in seasonal glacier snowpacks at sites extending 210 km along the Continental Divide and 100 km west of the divide supports the interpretation that Model 1 describes deposition in alpine glacier snowpack. Similar deposition values for the highest site in the Haig Valley and the mean from the regional snowpack study indicate the highest site in the Haig Valley represents regional conditions of S and N deposition. Summer deposition of sulfate (SO 4 2 ) and ammonium (NH 4 + ) was also consistent with dominantly distant emission sources (Model 1). In contrast there was enhanced transport and deposition of nitrate (NO 3  ) and nitrite (NO 2  ) in the summer to low elevations in the Haig Valley from local to regional emissions (Model 2). Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction Global levels of biologically available reactive inorganic nitro- gen (N), which is mainly nitrate (NO 3  ) and ammonium (NH 4 + ), were four times higher than preindustrial (1860) levels by the early 1990s and are projected to be eight times higher by 2050 (Galloway et al., 2004). Anthropogenic emissions, mainly from fos- sil fuel combustion, also contribute about 73% of global atmo- spheric sulfur (S) (Sofen et al., 2011). Nitrogen is released to the atmosphere predominantly as nitrogen oxides (NO x = NO + NO 2 ) from fossil fuel and biomass combustion and as ammonia (NH 3 ) from agricultural crop fertilization and animal excretion. NO x is oxidized in the atmosphere into HNO 3 and particulate NO 3  while http://dx.doi.org/10.1016/j.jhydrol.2015.01.073 0022-1694/Ó 2015 Elsevier B.V. All rights reserved. Abbreviations: N, inorganic nitrogen; NO 3  , nitrate; NH 4 + , ammonium; NO 2  , nitrite; NO x , nitrogen oxides (NO x = NO and NO 2 ); S, sulfur; SO 4 2 , sulfate; [NO 3  ], (square brackets designating concentration); NP, National Park; HDPE, high density polyethylene; DI, 18.2 O deionized water; masl, meters above sea level; HG2500, Haig Valley at 2500 masl; HG2640, Haig Valley at 2640 masl; HG2770, Haig Valley at 2770 masl; RB2500, Robertson Valley at 2500 masl; RB2800, Robertson Valley at 2800 masl; OP2400, Opabin Glacier at 2400 masl; WP2670, Wapta Icefield at 2670 masl; AT2820, Athabasca Glacier at 2820 masl; IC2490, Illicilewaet Glacier at 2490 masl; d.l., method detection limit; AWS, automatic weather station; RBAWS, Robertson Valley AWS; HGAWS, Haig Valley AWS; w.m., weighted mean; KS, Kananaskis Station; ppb, parts per billion; N–NO 3  , nitrogen component of nitrate; N–NH 4 + , nitrogen component of ammonium; SWE, snow water equivalent; CL Ndep , critical loads of N deposition; kg N ha 1 , kilograms of nitrogen per hectare; kg S ha 1 , kilograms of sulfur per hectare. ⇑ Corresponding author. E-mail addresses: vivian.wasiuta@queensu.ca (V. Wasiuta), melissa.lafreniere@- queensu.ca (M.J. Lafrenière), alnorman@ucalgary.ca (A.-L. Norman). Journal of Hydrology 523 (2015) 563–573 Contents lists available at ScienceDirect Journal of Hydrology journal homepage: www.elsevier.com/locate/jhydrol