Air Quality Monitoring

The WCAS air quality monitoring program focuses on acid-forming gases, air quality parameters that may affect vegetation, and parameters that are of interest to health professionals. Emphasis is placed on obtaining credible and scientifically defensible data. The quality control and quality assurance program includes daily checks of calibration and instrument performance, together with regular multi-point calibrations and government audits. Data is examined for long-term systematic errors and all raw and quality control data is archived.

Three types of air quality monitoring systems are used in the above programs:

1. Continuous monitoring equipment provides nearly instantaneous measurements of ambient concentrations of SO2, NOx, O3, particulate matter and hydrocarbons. Averages are calculated over five-minute and one-hour intervals to determine maximum and minimum atmospheric concentrations.
2. Integrated sampling systems are used to collect pollutants from the ambient atmosphere using reactive tubes, absorbents, and filters. This system samples a wide range of gases, fine and coarse particles, and semi-volatile organic compounds. The samples are chemically analysed to provide an average concentration of the pollutant over a specified sampling interval. These integrated sampling methods are more sensitive than the continuous monitors and are suitable for use in locations distant from major emission sources.
3. Passive sampling systems are used to collect integrated samples for analysis. Unlike the systems described above, they have no moving parts and require no electricity, making them suitable for use in remote locations.

Passive sytems have been developed for SO2, O3, NO2, and other gases, but are less precise than continuous and integrated methods.

Bio–Monitoring

When the West Central Airshed Zone was first established, stakeholders identified the effects of ambient air quality on vegetation as an important issue. Two of the main air quality issues identified by the public in the West Central zone were soil acidification and vegetative changes to agricultural crops and forests. To address the question of the vegetative effects of air quality a bio-monitoring program was developed to measure growth and yield, and to document visible symptoms of coincident air quality effects in representative indicator crops.

Alfalfa (Medicago sativa L.) and saskatoons (Amelanchier alnifolia) were selected as indicator species for growth and yield qualities. Both are sensitive to air quality and are grown commercially in the WCAS zone.

The WCAS's bio-monitoring program is a joint venture partnership with the Canadian Forest Service (CFS) and was established in 1997. Beginning in 2000 the program changed to a 5-year re-measurement period from a previous annual assessment. This was in keeping with the schedule for the entire Acid Rain National Early Warning System of plots. The Hightower and Steeper sites were visited in 1999 where the condition of trees had not changed since the plots were established. The vast majority of trees were in a healthy condition with no evidence of air pollutant stress.