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Published in:
2021 | OriginalPaper | Chapter
Urban Air Quality: Sources and Concentrations
Authors : Michael Evan Goodsite, Ole Hertel, Matthew Stanley Johnson, Nana Rahbek Jørgensen
Published in: Air Pollution Sources, Statistics and Health Effects
Publisher: Springer US
Excerpt
Aerodynamic diameter
Particles in ambient air have irregular shapes. The
aerodynamic diameter is the idealized spherical diameter with the same aerodynamic behavior as the irregular real-world particle.
Air pollutants
Anything in the air around us, man-made or natural, which contaminates the natural steady state of and constituents in the air as required for life categorized as gaseous or particulate pollutants.
Air pollution
The state of pollutants contaminating the air/atmosphere around us.
Air quality index (AQI)
A numerical index for air pollution, for example, in the UK, it is from 1 to 10 and related to the air quality bands of “low,” “moderate,” “high,” or “very high” (
https://uk-air.defra.gov.uk/air-pollution/daqi?view=more-info, accessed May 1st, 2019). Another example is the AQI from the US EPA with a scale from 0 “good” to 500 “hazardous”
https://airnow.gov/index.cfm?action=aqibasics.aqi (accessed May 1st, 2019).
Air quality
A subjective, often locally or nationally, determined state of the amount of pollutants in the air around us. The best air quality is when there are very low pollutant levels.
Ambient air
Air outside of structures at any given time. The “outdoor air” as opposed to the “air indoors.”
Atmosphere
The envelope of gases surrounding the Earth.
Coarse particles
The
coarse particle mass fraction is defined as the difference between measured PM
10 and PM
2.5 (see definitions of these).
Diffuse sources of air pollutants
Sources for which the release cannot easily be traced, e.g., that are not geocoded like gases and particle emissions from smaller industry and domestic heating, ammonia from grassing cattle, etc.
Emissions
The discharge of man-made or natural compounds into the environment.
Fine particles
The PM
2.5 fraction of particles (see definition of PM
2.5).
Particulates
Fine as well as coarse liquid and solid particles of organic or inorganic substances present in the atmosphere/suspended (floating) in the air. Particulate matter consists of very small liquid and solid particles floating in the air.
Photochemical smog
The resulting haze and reduced visibility from pollutants formed in reactions induced by sunlight (
photochemical reactions) and involving nitrogen oxides (NO
x) and hydrocarbons (HC). Photochemical smog
including elevated ozone (O
3) levels occurs generally on warm sunny days, which promotes photochemical reactions.
PM10
The mass concentration of particles with less than 10 microns (μm) in aerodynamic diameter. (PM
10) is generally used as an indicator for suspended particulate matter (e.g., regulated in EU directives) and routinely measured at many locations throughout the world.
PM2.5
The mass concentration of particles in the air with less than 2.5 microns (μm) in aerodynamic diameter. This fraction is often termed fine particles and capable of penetrating into the deepest parts of the lungs and thus causing great health concern.
Point (stationary) sources of air pollutants
Sources that emit pollutants from one given fixed location; this can, for example, be a power plant or an industrial plant.
Smog
A word combining “smoke” and “fog,” first used by Dr. HA Des Voeux in 1905. Smog is describing the poor visibility and often sharp, unpleasant, and soot pertaining haze that is occurring during periods when air pollutants are trapped at ground level. There are two processes producing smog: photochemical and physical processes, respectively, referred to as photochemical smog and urban smog.
Ultrafine particles
Particles in the size fraction below 0.1 micrometer in diameter. These particles are also often termed nanoparticles.
Urban air pollution
Ambient air in urban environments or areas that is (expectedly) polluted when compared with ambient air in pristine regions. There is generally a suite of pollutants that are measured/monitored to describe the resulting decrease in urban air quality.
Urban air quality
Refers to how “clean” the ambient air is inside of cities with a density, population, and level of activity that generally are recognized as “urban.”
Urban smog
Smog
where air pollutants particularly smoke and sulfur dioxide are trapped at ground level, usually occurring on cold, wind-still winter days. The Great London Smog episode of 1952 is a historical example still seen in developing countries in today. In western countries photochemical smog consisting of nitrogen oxides, ozone, and PAN is contemporarily more common.
Urban
An area with a large population, i.e., town or city, generally with a high density and large amount of population.
Winter smog
Winter smog
episodes including elevated levels of nitrogen oxides (NO
x) occur on cold calm days when air pollutants are trapped in urban areas by an inversion layer, i.e., a layer of warmer air above the wind-still cold air.