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, NO_x, 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.