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.
PM 10 The mass concentration of particles with less
than 10 microns (mm) 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.
PM 2.5 The mass concentration of particles in the
air with less than 2.5 microns (mm) 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, windstill 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.
Definition of the Subject and Its
Importance
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 air quality generally differs
from rural air quality since there are usually
194
Urban Air Quality: Sources and Concentrations
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.
PM 10 The mass concentration of particles with less
than 10 microns (mm) 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.
PM 2.5 The mass concentration of particles in the
air with less than 2.5 microns (mm) 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, windstill 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.
Definition of the Subject and Its
Importance
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 air quality generally differs
from rural air quality since there are usually
194
Urban Air Quality: Sources and Concentrations