Anthropogenic inputs of nitrogen to the environment have increased by over 150 %
in the last 150 years causing concern for vital biophysical processes on Earth. Thus being
able to measure these increased inputs in terrestrial, aquatic and atmospheric
environments is essential to understanding how the global nitrogen cycle has been
impacted since the industrial revolution. With respect to the atmosphere, emissions of
reduced and oxidized forms of nitrogen have increased largely due to the anthropogenic
activities of agriculture and combustion, respectively. Emissions of these nitrogenous
species not only impact regions adjacent to their point sources, but also have the ability to
influence ecosystems hundreds of kilometers away due to the long-range transport of
some of these compounds. This can impact sensitive remote ecosystems positively or
negatively by either stimulating growth or causing acidification, eutrophication and
biodiversity shifts. Therefore developing analytical techniques that are capable of
measuring oxidized and reduced atmospheric inputs to remote ecosystems is of great
importance.
In part I of this work a method employing custom-built physisorption-based passive
samplers coupled with ion chromatography analysis was developed to sample
atmospheric nitric acid (HNO₃(g)) in remote ecosystems. The developed HNO₃(g) sampling
method was able to detect HNO₃(g) mixing ratios as low as 2 parts per trillion by volume
(pptv) over a monthly sampling period, following a rigorous quality assurance and quality
control procedure. The passive samplers were installed across the Newfoundland and
Labrador – Boreal Ecosystem Latitudinal Transect (NL-BELT) in the summer of 2015, and average mixing ratios of HNO₃(g) at the NL-BELT field sites from 2015-16 were
determined to be in the tens of parts per trillion by volume (pptv) range. The dry
deposition flux of HNO₃(g) as nitrogen (N) to the field sites ranged from 3 – 16 mg N yr-1.
Through an air mass back trajectory analysis, coupled with a steady-state chemical box
model approximation, it was determined that the HNO₃(g) quantities observed at a single
NL-BELT site likely originated from local production and regional transport from central
and eastern Newfoundland, with an additional contribution from the down welling of
peroxyacetyl nitrates from the upper troposphere, possibly occurring during the spring
and early summer.
In part II of this work, an ion chromatography method was developed to speciate
and quantify alkylamines (NR₃(g)). NR₃(g) have been shown to influence Earth’s climate
and may be an important source of new nitrogen to remote ecosystems. The developed
method was shown to be sensitive, accurate, and robust in separating and quantifying 11
atmospheric alkylamines, including 3 sets of alkylamine isomers, from 5 common
atmospheric inorganic cations. The method was able to detect NR₃(g) at a picogram per
injection level, and the method performed robustly in the presence of a complex biomassburning
matrix containing amounts of inorganic cations up to 3 orders of magnitude
larger than the NR₃(g) quantified in the samples. Thus the ion chromatography method can
be applied to the remote atmosphere where alkylamine concentrations are often detected
in quantities 1000 times less than other atmospheric cations. In the biomass-burning
particle samples tested using the ion chromatography method unprecedented quantities of
dimethylamine and diethylamine were observed, with the summed molar quantity
exceeding that of ammonium in the 100 – 560 nm particle diameter fraction.
The applicability of these atmospheric measurement techniques to measure and
quantify HNO₃(g) and NR₃(g) has been demonstrated for remote ecosystems and will
hopefully allow for a greater understanding of these two species roles’ in remote
environments