8.3 Urban air pollution

PM10

A component of air pollution that is made of larger particulate matter with a diameter of 10 micrometres or less

PM2.5

A component of air pollution that is made of fine particulate matter with a diameter of 2.5 micrometres or less

Primary pollutants

directly active at the point of emission

Catalytic converter

An exhaust emission control device designed to reduce toxic gases and pollutants in the exhaust gas of internal combustion engines.

Peroxyacyl nitrates (PANs)

A secondary pollutant and component of photochemical smog, produced in the atmosphere when oxidized volatile organic compounds combine with nitrogen oxide.

Photochemical smog (HL)

formed when sunlight acts on primary pollutants causing their chemical transformation into secondary pollutants

Temperature inversion

This occurs due to a lack of air movement when a layer of dense, cool air is trapped beneath a layer of less dense, warm air. This causes concentrations of air pollutants to build up near the ground instead of being dissipated by "normal" air movements.

Urban air pollution

caused by inputs from human activities to atmospheric systems, including nitrogen oxides (NOx), sulfur dioxide, carbon monoxide and particulate matter

Primary pollutants

directly active at the point of emission

Acid rain

NOx and sulfur dioxide react with water and oxygen in the air to produce nitric and sulfuric acid, resulting in acid rain

scrubbers

devices containing alkaline substances that precipitate out much of the sulfur dioxide from industrial plants.

catalytic converters

Used in a car to convert toxins such as CO, NO, NO2 and hydrocarbons to harmless gases, like nitrogen and carbon dioxide.

tropospheric ozone

Human produced ozone, a result of air pollution