Ambient concentrations of atmospheric ammonia, nitrogen dioxide and nitric acid across a rural–urban–agricultural transect in southern Ontario, Canada

TitleAmbient concentrations of atmospheric ammonia, nitrogen dioxide and nitric acid across a rural–urban–agricultural transect in southern Ontario, Canada
Publication TypeJournal Article
Year of Publication2012
AuthorsZbieranowski AL, Aherne J.
JournalAtmospheric environment
Volume62
Pagination481-491
Abstract

The spatial and temporal variation in ambient atmospheric concentrations of gaseous reactive nitrogen (Nr) species (ammonia [NH₃], nitrogen dioxide [NO₂] and nitric acid [HNO₃]) were measured at four sites (spanning a transect in land use types: intensive agricultural, urban–agricultural transition, urban, and rural background) across southern Ontario, Canada. Atmospheric concentrations were measured with the Willems badge diffusive passive sampler for one year (April 2010–March 2011) at two-week exposure periods (biweekly integrated concentration measurements); dry deposition was estimated using the inferential method. There was high spatial and temporal variability in the ambient concentrations and estimated dry deposition of NH₃, NO₂ and HNO₃ across the four study sites. Annual average Nr concentrations were greatest at the urban site owing to high NO₂ concentrations (>25 μg m⁻³), while annual average ambient NH₃ concentrations were greatest at the intensive agricultural site (>3 μg m⁻³) followed by the urban site (∼2 μg m⁻³) suggesting that outside of intensive agricultural areas, urban regions have the highest ambient NH₃ concentrations in southern Ontario. The high ambient NH₃ and NO₂ concentrations resulted in high dry deposition of gaseous Nr (urban [>12 kg N ha⁻¹ yr⁻¹] and intensive agricultural [>8 kg N ha⁻¹ yr⁻¹]), accounting for 50–60% of estimated total Nr deposition (dry gaseous + wet ammonium and nitrate) at the study sites. 

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