Monitoring Programs

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.


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.

Preamble to the Dr. Herman Sievering Statistical Report

The West Central Airshed Society identified a need to understand the effects of air quality on agriculture in the early days of the airshed. For the last fifteen years WCAS has operated an agriculture program designed to measure the effects of air quality on two sensitive agricultural crops, co-located with five continuous air monitoring stations. Each year crop growth and crop quality was measured and the crop data analyzed in relation to the continuous air quality data, including meteorological data, by a group of agricultural specialists. Dr. Sagar Krupa led the study that was designed to determination if there is a correlation between air quality and crop production. This was an extensive study conducted over a number of years in the central Alberta region. The report verifies that there is a relationship between air quality and crop production; however, it suggests more study would be required to quantify the relationship. Dr. Krupa's report is available on the WCAS website under the section on reports.

WCAS still saw value in trying to define the correlation and to develop a formula that could be used to do a calculation of crop damage due to air quality. Dr. Herman Sievering, a statistician from the University of Colorado was contracted to look at all the data that had been collected and analyzed by Dr. Krupa. A statistical analysis was thought to be able to produce a formula for the calculation of a correlation between air quality and crop production.

Dr. Sievering produced a document with his findings; his report is available on request. From a statistical point of view the report does produce a formula of correlation. However, two peer reviews conducted by highly respected air quality scientists with specific local knowledge have disagreed strongly with Dr. Sievering's report. Two other peer reviews conducted by statisticians agreed with the results of the report.

The WCAS Board will not be using the formula as a tool to measure the influence of air quality. WCAS will continue to operate a modified Ag program. In the event of a major air quality issue crop damage will be accessed on an actual basis. Data generated from an actual event is expected to provide a robust and defensible correlation.

Air Quality Data

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