The Southern Ontario Ammonia Passive Sampler Survey (SOAPSS) ran from April 4, 2006 to March 27, 2007. The objective of the study was to measure weekly/biweekly concentrations of ambient ammonia at approximately 78 sites in southern Ontario and at a small number of sites outside of Ontario and in the northern Great Lakes states. Eleven NADP and CASTNET sites kindly collaborated in the study, providing site access and operator support. Two types of passive samplers and two sampling periods were used. From April 4 to November 21, 2006, weekly sampling was carried out using Ogawa passive samplers at sites in the agricultural areas and P25 passive samplers (a customized larger version of the Ogawas) in the non-agricultural areas; after November 21, 2006, bi-weekly sampling was done in all areas using the P25s only. Both types of passive samplers were collocated at several sites for comparison and, at one site, also collocated with a continuous ammonia monitor and a denuder/filter pack system.

Results of the study confirm that ambient ammonia concentrations are high in the intense agricultural areas of southwestern Ontario and low in the non-agricultural areas of south-central and southeastern Ontario. In fact, the spatial pattern of SOAPSS ambient ammonia concentrations corresponds closely to the pattern of ammonia emissions. Southwestern Ontario concentrations, although high for eastern Canada, were lower than those measured in the intensive agricultural areas of western Canada (i.e., in British Columbia, Alberta and Manitoba). Concentrations measured at the U.S. NADP and CASTNET sites were generally in the same low concentration range as the Ontario sites, with the exception of the Aurora, NY site, which had relatively high concentrations. A full summary of SOAPSS results will be given.