Passive Sampling of Ammonia in Ontario (2007–2010)
Antoni Zbieranowski* and Julian Aherne
Environmental and Resource Studies
Trent University, Peterborough, ON K9J 7B8
Elevated emissions of atmospheric reactive nitrogen (Nr) have lead to concerns that Nr deposition may result in long-term negative impacts on natural ecosystems e.g., acidification, eutrophication and decreased biodiversity. Atmospheric ammonia (NH3), is the dominant Nr species emitted in agricultural regions, moreover recent studies have shown significant emissions in urban centres owing to emissions from vehicle exhaust. Atmospheric concentrations of NH3 are highly variable, both spatially and temporally, owing to its high deposition velocity. Continuous observations of NH3 are limited, within Ontario there is only one station with ongoing NH3 monitoring: Centre for Atmospheric Research Experiments (CARE) Environment Canada. Passive samplers have been widely used to capture the spatial variability as they provide a low cost method requiring no power and can be deployed across many sites. In the current study, ambient NH3 concentrations have been monitored across southern Ontario in regions of intensive agricultural activity, rural background regions and more recently in the urban centre of Toronto using the Willems badge passive sampler. Since August 2007, the samplers have been exposed in triplicate at two week intervals, at approximately 40 sites (continuous at 2: CARE and Dorset). The Willems badge has been evaluated against other passive samplers (Gradko, Radiello® and Ogawa) and shown significant correlation with a modified Thermo 42C trace level chemiluminescence based analyzer (R2 = 0.86) and an active denuder system (R2 = 0.71). Ammonia concentrations varied spatially across southern Ontario and temporally throughout the year peaking in the spring in agricultural regions and the summer in urban and background regions; concentrations were the lowest in the winter. At CARE (low intensity agriculture) and Dorset (background), annual average NH3 concentrations ranged between 0.10 – 4.12 µg m–3 and 0.00 – 0.54 µg m–3 respectively during 2007 to 2009. The largest range in NH3 concentrations was observed in intensive agricultural regions with a low of 0.38 µg m–3 (February 2008) and peaking at 18.98 µg m–3 (May 2008). Ammonia concentrations in Toronto ranged from 1.55 – 4.65 µg m–3 (winter – summer, 2010).
*Corresponding author: E-mail: ; Telephone: (705) 748-1011 ext. 7959 ERS, Trent University, 1600 West Bank Drive, Peterborough, Ontario, Canada K9J 7B8