Detection and quantification of reactive atmospheric nitrogen species in remote ecosystems

• Main Author: Place, Bryan K.
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2017
• Subjects: Newfoundland
• Online Access: https://research.library.mun.ca/12950/; https://research.library.mun.ca/12950/1/thesis.pdf

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 ...