| Elevated chronic emissions of reactive nitrogen (Nr) have lead to concerns that atmospheric nitrogen (N) is impacting ecosystem sustainability. Current atmospheric monitoring networks across southern Ontario have limited observations of gaseous Nr species. The objective of this thesis was to assess the spatial and temporal variability in gaseous Nr (ammonia [NH3], nitrogen dioxide [NO2] and nitric acid) concentrations across dominant land use regions (intensive agriculture, urban-agricultural transition, urban, rural background) in southern Ontario. Gaseous Nr was measured for one year (April 2010---March 2011) with the Willems badge passive diffusive sampler (bi-weekly sampling) and dry deposition was estimated by the inferential method. Gaseous NH3 and NO2 dominated total N deposition across much of southern Ontario suggesting that current networks potentially underestimated total N deposition by > 50 %. Wide-spread measurements of NH3 and NO2 are recommended to be incorporated in current air monitoring networks to support regional assessments of impacts of Nr on semi-natural ecosystems in southern Ontario.;Keywords: Agricultural emissions, Ambient concentration, Ammonia, Dry deposition, Nitric acid, Nitrogen dioxide, Passive diffusive sampler, Urban emissions, Willems badge... |
