Nitrogen Deposition to an Alberta Bog as Measured with Mixed-bed Ion Exchange Resin Tube Collectors, 2011-2015

Development of the oil sands has led to increasing atmospheric N deposition, with values as high as 17 kg N ha-1 yr-1; regional background levels <2 kg N ha-1 yr-1. Bogs, being ombrotrophic, may be especially susceptible to increasing N deposition. To examine responses to N deposition, over five years, we experimentally applied N (as NH4NO3) to a bog near Mariana Lakes, Alberta, at rates of 0, 5, 10, 15, 20, and 25 kg N ha-1 yr-1, plus controls (no water or N addition). Resin tubes filled with mixed-bed ion exchange resin were swapped in and out at each collection/deployment date (mid-May and mid-October of each year). Upon collection, resins were extracted with 1M KI and analyzed for inorganic N concentrations. Deposition of NH4 +-N, NO3 --N, and DIN averaged 187 ± 11, 237 ± 13, and 426 ± 19 μg m-2 da-1, corresponding to 0.68 ± 0.04, 0.87 ± 0.05, and 1.55 ± 0.07 kg N ha-1 yr-1, with no significant differences between open and throughfall collectors for any of the three measured parameters (p >= 0.63). Deposition of NH4 +-N was significantly higher during the growing season (averaging 240 μg m-2 da-1) than during the winter months (averaging 121 μg m-2 da-1) (p = 0.0004), while NO3 --N and DIN deposition did not differ significantly between winter and summer (p = 0.06 and 0.13, respectively).