Evaluation of Ammonia Measurements from CASTNet, IMPROVE, Passive and a New Sampling System

Derek Day
Colorado State University-CIRA,
Fort Collins, CO USA

Atmospheric ammonia is a major pollutant and the most abundant alkaline component in the atmosphere. The primary emission source of ammonia is from livestock operations associated with agricultural activities. In high emission regions, ammonia can lead to the acidification and eutrophication of soils and surface waters in semi-natural ecosystems. Despite the importance of atmospheric ammonia very little monitoring of this gas is carried out in Ontario. Environment Canada’s Centre for Atmospheric Research Experiments in Egbert Ontario is the only location that continuously monitors ambient ammonia concentrations. The objective of the current study is to determine the spatial and temporal variation of ambient ammonia concentration in south central Ontario. Ten study sites were selected along a gradient of high to low agricultural intensity. Ammonia is being measured using a passive sampler (requires no power) known as a Willems badge (constructed, prepared and analysed at Trent University). Sampling is being carried out on a biweekly basis from August 2007 to August 2008. Samples are analysed using a colourimetric method for ammonia (wavelength of 655 nm). Results to date show a consistent increase in ammonia concentrations from late September through October and decrease from November to mid December across all sites with consistent low levels during the winter months to mid March where ammonia concentrations start to increase slightly and spike in mid to late April noted by site operators as a time when fertilizers and manure were heavily spread in the sampling areas of mid to high agricultural intensity. Spatially higher average ammonia levels (3.0–5.0 µg/m3) are observed in regions of high agricultural intensity (0.1–1.0 µg/m3 in low agricultural intensity areas). The normalised concentrations show synchronicity in levels at medium and high intensity agricultural regions and more variation in the low intensity agricultural regions indicating that although concentrations vary spatially the temporal trend in fluctuating ammonia concentrations follow a similar pattern across south central Ontario.