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 NH 4 NO 3 ) 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
NH 4 + -N,
NO 3 - -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
NH 4 + -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
NO 3 - -N and DIN
deposition did not differ significantly between winter and summer (p =
0.06 and 0.13, respectively).