OZONE CONCENTRATIONS AT A REMOTE MOUNTAIN SITE AND AT 2 REGIONAL LOCATIONS IN SOUTHWESTERN ALBERTA

Ozone concentrations at a remote site in the Rocky Mountains of southwestern Alberta averaged 43.4 ppb over a 2 year period and the Canadian air quality objective of an 80 ppb hourly average was exceeded 1.5% of the time. The diurnal variation in O3 concentrations was small, 2.9 ppb, indicative of a remote location, above the nocturnal inversion and not greatly influenced by local emissions. During the period when O3 concentrations were highest, winds were generally from the southwest, suggestive of the long range transport of anthropogenic pollutants from distant sources rather than the generation of O3 from local emissions. In contrast, hourly O3 concentrations at two regional air quality monitoring sites showed an average diurnal variation of 14 ppb. Only two hourly averages exceeded 80 ppb during the 2 years, and the mean O3 concentration was 26 ppb. When these regional sites were within the urban plume from Calgary, the O3 concentrations were depressed to a mean of 18 ppb. Ozone concentrations in downtown Calgary averaged 13 ppb. Under Alberta climatological and meteorological conditions, hourly O3 objectives are most likely to be exceeded in remote areas, rather than in cities or in areas under the direct influence of urban emissions. © 1990.