Ozone (O₃)

Unlike other pollutants, ozone (O₃) is not emitted directly by human activities. O₃ in the lower atmosphere is produced by a complicated set of chemical reactions involving oxides of nitrogen (NO_x) and volatile organic compounds (VOCs) in the presence of sunlight. O₃ is also transported to the ground from the "ozone rich" upper atmosphere by natural weather processes. O₃ and its precursors, such as NO_x and VOCs, may also be carried from upwind sources such as urban centres and industrial complexes. A major source of VOCs in rural areas is natural emissions from trees and vegetation.

O₃ concentrations are generally lower at urban locations than at rural locations. This is due to the destruction of O₃ by nitric oxide (NO) that is emitted by vehicles. O₃ levels are usually higher during the spring and summer months because of more transport from the upper atmosphere and more sunlight with allows O₃ forming chemical reactions to occur more rapidly.

At normal outdoor concentrations, O₃ is a colourless, odourless gas. However, O₃ does have a characteristic of sharp odour when at very high concentrations, such as that associated with lightning storms.

Objectives
The Objectives for O₃ are based on the prevention of adverse effects to human health and vegetation. The ambient air quality Objectives for O₃ in Alberta are:

0.082 ppm (parts per million) as a 1-hour average concentration.

The Canada-wide Standard (CWS) benchmark concentration for 8-hour O₃ concentrations is 0.065 ppm. The actual achievement statistic for the O₃ CWS is based on a complex calculation process that involves using the fourth highest measurement annually, averaged over three consecutive years.

Monitoring Methods
An ultra-violet (UV) light process is used o continuously monitor O₃. The sampled air is exposed to UV light, which is absorbed by O₃. The amount of UV light absorbed is proportional to the amount of O₃ in the sample; that is, the more UV light is absorbed, the greater the amount of O₃ in the sample.

	Ozone (O₃) Unlike other pollutants, ozone (O₃) is not emitted directly by human activities. O₃ in the lower atmosphere is produced by a complicated set of chemical reactions involving oxides of nitrogen (NO_x) and volatile organic compounds (VOCs) in the presence of sunlight. O₃ is also transported to the ground from the "ozone rich" upper atmosphere by natural weather processes. O₃ and its precursors, such as NO_x and VOCs, may also be carried from upwind sources such as urban centres and industrial complexes. A major source of VOCs in rural areas is natural emissions from trees and vegetation. O₃ concentrations are generally lower at urban locations than at rural locations. This is due to the destruction of O₃ by nitric oxide (NO) that is emitted by vehicles. O₃ levels are usually higher during the spring and summer months because of more transport from the upper atmosphere and more sunlight with allows O₃ forming chemical reactions to occur more rapidly. At normal outdoor concentrations, O₃ is a colourless, odourless gas. However, O₃ does have a characteristic of sharp odour when at very high concentrations, such as that associated with lightning storms. Objectives The Objectives for O₃ are based on the prevention of adverse effects to human health and vegetation. The ambient air quality Objectives for O₃ in Alberta are: 0.082 ppm (parts per million) as a 1-hour average concentration. The Canada-wide Standard (CWS) benchmark concentration for 8-hour O₃ concentrations is 0.065 ppm. The actual achievement statistic for the O₃ CWS is based on a complex calculation process that involves using the fourth highest measurement annually, averaged over three consecutive years. Monitoring Methods An ultra-violet (UV) light process is used o continuously monitor O₃. The sampled air is exposed to UV light, which is absorbed by O₃. The amount of UV light absorbed is proportional to the amount of O₃ in the sample; that is, the more UV light is absorbed, the greater the amount of O₃ in the sample.

Ozone (O3)

Ozone (O₃)