Air Quality Health Index
Real-time information system that provides the public with an indication of air quality in cities, towns and in rural areas across Ontario. The AQHI derives a value based on the cumulative health effects of three pollutants – O3, PM2.5 and NO2.
AQHI station
Continuous monitoring station used to inform the public of general ambient air quality levels over an entire region (not a localized area) on a real-time basis; station reports on criteria pollutant levels that are not unduly influenced by a single emission source, but rather are the result of emissions from multiple sources, including those in neighbouring provinces and states.
Ambient air
Outdoor or open air.
Ambient monitoring
Measurements of regional air quality less influenced by local and industrial sources of air contaminants.
Annual mean
The average value of data for a given year.
Area sources
Small collective emission sources that are inventoried as a group, such as any small residential, governmental, institutional, commercial or industrial fuel combustion operations, which are too numerous to inventory as point sources.
Black carbon
The sooty black material produced through incomplete combustion processes. It is emitted from anthropogenic (e.g., engines and coal-fired power plants) and natural sources (e.g., forest fires). BC comprises a significant portion of fine particulate matter and is linked to both climate warming and adverse health effects.
Carbon monoxide
A colourless, odourless, tasteless, and at high concentrations, poisonous gas.
Continuous pollutants
Pollutants for which a continuous measurement record exists; effectively, pollutants that have hourly data (maximum 8,760 values per year except leap year – e.g. 2004 where maximum values for the year are 8,784).
Continuous station
Where pollutants are measured on a real-time basis and data determined hourly (for example ozone, sulphur dioxide).
Maximum concentration or level (based on potential effects) of pollutant that is desirable or considered acceptable in ambient air.
The direction the wind is going to. If the wind is blowing towards the Southeast (blowing from the Northwest), then the downwind direction is towards the Southeast and the upwind direction is towards the Northwest.
Above the air pollutant concentration levels established by environmental protection criteria or other environmental standards.
Fine Particulate Matter
Also referred as respirable particles: particles smaller than 2.5 micrometres in aerodynamic diameter, which arise mainly from fuel combustion, condensation of hot vapors and chemically driven gas-to-particle conversion processes; also referred to as PM2.5 or respirable particles. These are fine enough to penetrate deep into the lungs.
Fossil fuels
Natural gas, petroleum, coal and any form of solid, liquid or gaseous fuel derived from organic materials for the purpose of generating heat.
Fly ash
Generated as a by-product of coal combustion and is used as a replacement for cement in concrete, among other uses
Ground-level ozone
Colourless gas formed from chemical reactions between nitrogen oxides and volatile organic compounds (VOCs) in the presence of sunlight near the Earth's surface.
Mann-Kendall (M-K) test
A nonparametric statistical approach that can be applied to data without making assumptions on the nature of the data distribution. The M-K test is suitable for environmental monitoring data to handle missing, trace and below detection limit values.
Meteorological conditions
The conditions in the atmosphere (e.g. temperature, air pressure, water vapour, air flows, etc.), and the variations (over time and space, both vertically and horizontally) and interactions of these conditions.
Concentrations measured at a monitoring station calculated in the statistical form of a standard.
A millionth of a metre.
Natural sources
Emission sources such as biogenic emissions from vegetation, biological and geological sources, wildfires, and other sources not made by humans.
Nitrogen dioxide
A reddish-brown gas with a pungent and irritating odour.
Open sources
Emission sources that emit air contaminants over large geographical areas. Examples include dust from farms, construction, and paved and unpaved roads.
A chemical reaction where a substance gains an oxygen; for example, in the atmosphere, sulphur dioxide is oxidized by hydroxyl radicals to form sulphate.
Particulate matter
The general term used to describe a mixture of microscopic solid particles and liquid droplets suspended in air.
Point sources
Sources that have a fixed location and are identified individually by name and location.
Primary pollutant
Pollutant emitted directly to the atmosphere.
Residence time
The average length of time during which a particle is in a given location or condition.
Respirable particles
See definition for fine particulate matter.
Secondary pollutant
pollutant formed from other pollutants in the atmosphere.
Sen’s slope
The Sen’s slope (also known as the Thiel-Sen’s estimator) is closely-related to and applied in conjunction with the Mann-Kendall Test. Compared to the common least squares regression, the Sen’s slope procedure is a nonparametric method for computing the value of the true slope when there are gross errors or outliers in the data (Gilbert, 1987) without making assumptions of a normal distribution on the data.
A contraction of smoke and fog; colloquial term used for photochemical smog, which includes ozone, fine particulate matter and other contaminants; tends to be a brownish haze.
Atmosphere 10 to 40 kilometres above the Earth's surface.
Stratospheric ozone
Ozone formed in the stratosphere from the conversion of oxygen molecules by solar radiation; ozone found there absorbs some of the sun’s ultraviolet radiation and prevents it from reaching the Earth.
Primarily a synthetic chemical that is used extensively in the manufacture of plastics, rubber, and resins. It is also known as vinylbenzene, ethenylbenzene, cinnamene, or phenylethylene.
Sulphur dioxide
A colourless gas that smells like burnt matches.
Transportation sources
Mobile emission sources such as wheeled vehicles, ships, aircraft and railroad locomotives.
Atmospheric layer extending from the surface up to about 10 kilometres above the Earth's surface.
Ultrafine particles
Particles that are less than 0.1 µm in aerodynamic diameter; mostly emitted from road traffic in urban environments. These tiny particles have larger surface areas per unit mass to absorb toxic chemicals and can penetrate deep into the lungs.
The direction the wind is coming from. If the wind is blowing from the Northwest (blowing toward the Southeast) then the upwind direction is toward the Northwest and the downwind direction is toward the Southeast.