Unit-V
Environmental Pollution and Control
Air pollution: Air pollution occurs when harmful substances including particulates and biological
molecules are introduced into Earth's atmosphere. It may cause diseases, allergies or death of
humans; it may also cause harm to other living organisms such as animals and food crops, and
may damage the natural or built environment. Human activity and natural processes can both
generate air pollution.
Air pollution may be defined as the presence of any solid, liquid or gaseous substance including
noise and radioactive radiation in the atmosphere in such concentration that may be directly and
indirectly injurious to humans or other living organisms, plants, property or interferes with the
normal environmental processes.
Types of pollutants: Air pollution occurs in many forms but can generally be thought of as
gaseous and particulate contaminants that are present in the earth's atmosphere. Gaseous pollutants
include sulfur dioxide (SO2), nitrogen oxides (NOx), ozone (O3), carbon monoxide (CO), volatile
organic compounds (VOC), hydrogen sulfide (H2S), hydrogen fluoride (HF), and various gaseous
forms of metals. These pollutants are emitted from large stationary sources such as fossil fuel fired
power plants, smelters, industrial boilers, petroleum refineries, and manufacturing facilities as well
as from area and mobile sources. They are corrosive to various materials which causes damage to
cultural resources, can cause injury to ecosystems and organisms, aggravate respiratory diseases,
and reduce visibility.
Particulates come in both large and small or "fine" solid forms. Large particulates include
substances such as dust, asbestos fibers, and lead. Fine particulates include sulfates (SO4) and
nitrates (NO3). Important sources of particulates are power plants, smelters, mining operations,
and automobiles. Asbestos and lead affect organisms, while sulfates and nitrates not only cause
health problems, but also contribute to acid rain or acid deposition and a reduction in visibility.
Particulate matter, a term sometimes used instead of particulates, refers to the mixture of solid
particles and liquid droplets found in the air.
1
,Toxic air pollutants are a class of chemicals which may potentially cause health problems in a
significant way. The sources of toxic air pollutants include power plants, industries, pesticide
application, and contaminated windblown dust. Persistent toxic pollutants, such as mercury, are of
particular concern because of their global mobility and ability to accumulate in the food chain.
More research is needed to fully understand the fate and effects of mercury and the many other
toxic pollutants.
Primary pollutants are those that are emitted directly into the air from pollution sources. Secondary
pollutants are formed when primary pollutants undergo chemical changes in the atmosphere.
Ozone is an example of a secondary pollutant. It is formed when nitrogen oxides (NOx) and
volatile organic compounds (VOCs) are mixed and warmed by sunlight. Ozone (O3) is a major
component of what is often referred to as smog. The ozone which is present in the troposphere, or
the atmosphere that is close to the ground, should not be confused with beneficial ozone that is
located in the stratosphere or upper atmosphere. This beneficial ozone in the stratosphere helps
protect the earth from harmful ultraviolet light from the sun.
Stationary and Area Sources
A stationary source of air pollution refers to an emission source that does not move, also known
as a point source. Stationary sources include factories, power plants, dry cleaners and degreasing
operations. The term area source is used to describe many small sources of air pollution located
together whose individual emissions may be below thresholds of concern, but whose collective
emissions can be significant. Residential wood burners are a good example of a small source, but
when combined with many other small sources, they can contribute to local and regional air
pollution levels. Area sources can also be thought of as non-point sources, such as construction of
housing developments, dry lake beds, and landfills.
Sources of Air Pollution: On-road vehicles: 56%, Non-road Vehicles & Engines: 22%, Industrial
process: 4%, Fuel Combustion: 6% and Miscellaneous: 12%
Mobile Sources: A mobile source of air pollution refers to a source that is capable of moving
under its own power. In general, mobile sources imply "on-road" transportation, which includes
vehicles such as cars, sport utility vehicles, and buses. In addition, there is also a "non-road" or
2
, "off-road" category that includes gas-powered lawn tools and mowers, farm and construction
equipment, recreational vehicles, boats, planes, and trains.
Agricultural Sources: Agricultural operations, those that raise animals and grow crops, can
generate emissions of gases and particulate matter. For example, animals confined to a barn or
restricted area (rather than field grazing), produce large amounts of manure. Manure emits various
gases, particularly ammonia into the air. This ammonia can be emitted from the animal houses,
manure storage areas, or from the land after the manure is applied. In crop production, the
misapplication of fertilizers, herbicides, and pesticides can potentially result in aerial drift of these
materials and harm may be caused.
Natural Sources: Although industrialization and the use of motor vehicles are overwhelmingly
the most significant contributors to air pollution, there are important natural sources of "pollution"
as well. Wildland fires, dust storms, and volcanic activity also contribute gases and particulates to
our atmosphere.
Unlike the above mentioned sources of air pollution, natural "air pollution" is not caused by people
or their activities. An erupting volcano emits particulate matter and gases; forest and prairie fires
can emit large quantities of "pollutants"; plants and trees naturally emit VOCs which are oxidized
and form aerosols that can cause a natural blue haze; and dust storms can create large amounts of
particulate matter. Wild animals in their natural habitat are also considered natural sources of
"pollution".
Air Pollution Effects: The presence of pollution in the atmosphere results directly in air quality
degradation. Air pollution is also a critical factor affecting the quality of other environmental
resources as well as the human-made structures and facilities in the area. Polluted air can and has
harmed park resources in a variety of ways depending upon the chemistry of the pollutant, weather
and environmental conditions, and the nature or sensitivity of resources. Examples of this harm
include vegetative discoloration and growth disruption from ozone, loss of aquatic species from
stream acidification, shifts in nutrient availability from acid deposition, and erosion of building
surfaces and rock formations. Air pollution impairs visibility and contributes to climate change.
Air pollution can also be detrimental to human health.
Major Air pollutants
3
Environmental Pollution and Control
Air pollution: Air pollution occurs when harmful substances including particulates and biological
molecules are introduced into Earth's atmosphere. It may cause diseases, allergies or death of
humans; it may also cause harm to other living organisms such as animals and food crops, and
may damage the natural or built environment. Human activity and natural processes can both
generate air pollution.
Air pollution may be defined as the presence of any solid, liquid or gaseous substance including
noise and radioactive radiation in the atmosphere in such concentration that may be directly and
indirectly injurious to humans or other living organisms, plants, property or interferes with the
normal environmental processes.
Types of pollutants: Air pollution occurs in many forms but can generally be thought of as
gaseous and particulate contaminants that are present in the earth's atmosphere. Gaseous pollutants
include sulfur dioxide (SO2), nitrogen oxides (NOx), ozone (O3), carbon monoxide (CO), volatile
organic compounds (VOC), hydrogen sulfide (H2S), hydrogen fluoride (HF), and various gaseous
forms of metals. These pollutants are emitted from large stationary sources such as fossil fuel fired
power plants, smelters, industrial boilers, petroleum refineries, and manufacturing facilities as well
as from area and mobile sources. They are corrosive to various materials which causes damage to
cultural resources, can cause injury to ecosystems and organisms, aggravate respiratory diseases,
and reduce visibility.
Particulates come in both large and small or "fine" solid forms. Large particulates include
substances such as dust, asbestos fibers, and lead. Fine particulates include sulfates (SO4) and
nitrates (NO3). Important sources of particulates are power plants, smelters, mining operations,
and automobiles. Asbestos and lead affect organisms, while sulfates and nitrates not only cause
health problems, but also contribute to acid rain or acid deposition and a reduction in visibility.
Particulate matter, a term sometimes used instead of particulates, refers to the mixture of solid
particles and liquid droplets found in the air.
1
,Toxic air pollutants are a class of chemicals which may potentially cause health problems in a
significant way. The sources of toxic air pollutants include power plants, industries, pesticide
application, and contaminated windblown dust. Persistent toxic pollutants, such as mercury, are of
particular concern because of their global mobility and ability to accumulate in the food chain.
More research is needed to fully understand the fate and effects of mercury and the many other
toxic pollutants.
Primary pollutants are those that are emitted directly into the air from pollution sources. Secondary
pollutants are formed when primary pollutants undergo chemical changes in the atmosphere.
Ozone is an example of a secondary pollutant. It is formed when nitrogen oxides (NOx) and
volatile organic compounds (VOCs) are mixed and warmed by sunlight. Ozone (O3) is a major
component of what is often referred to as smog. The ozone which is present in the troposphere, or
the atmosphere that is close to the ground, should not be confused with beneficial ozone that is
located in the stratosphere or upper atmosphere. This beneficial ozone in the stratosphere helps
protect the earth from harmful ultraviolet light from the sun.
Stationary and Area Sources
A stationary source of air pollution refers to an emission source that does not move, also known
as a point source. Stationary sources include factories, power plants, dry cleaners and degreasing
operations. The term area source is used to describe many small sources of air pollution located
together whose individual emissions may be below thresholds of concern, but whose collective
emissions can be significant. Residential wood burners are a good example of a small source, but
when combined with many other small sources, they can contribute to local and regional air
pollution levels. Area sources can also be thought of as non-point sources, such as construction of
housing developments, dry lake beds, and landfills.
Sources of Air Pollution: On-road vehicles: 56%, Non-road Vehicles & Engines: 22%, Industrial
process: 4%, Fuel Combustion: 6% and Miscellaneous: 12%
Mobile Sources: A mobile source of air pollution refers to a source that is capable of moving
under its own power. In general, mobile sources imply "on-road" transportation, which includes
vehicles such as cars, sport utility vehicles, and buses. In addition, there is also a "non-road" or
2
, "off-road" category that includes gas-powered lawn tools and mowers, farm and construction
equipment, recreational vehicles, boats, planes, and trains.
Agricultural Sources: Agricultural operations, those that raise animals and grow crops, can
generate emissions of gases and particulate matter. For example, animals confined to a barn or
restricted area (rather than field grazing), produce large amounts of manure. Manure emits various
gases, particularly ammonia into the air. This ammonia can be emitted from the animal houses,
manure storage areas, or from the land after the manure is applied. In crop production, the
misapplication of fertilizers, herbicides, and pesticides can potentially result in aerial drift of these
materials and harm may be caused.
Natural Sources: Although industrialization and the use of motor vehicles are overwhelmingly
the most significant contributors to air pollution, there are important natural sources of "pollution"
as well. Wildland fires, dust storms, and volcanic activity also contribute gases and particulates to
our atmosphere.
Unlike the above mentioned sources of air pollution, natural "air pollution" is not caused by people
or their activities. An erupting volcano emits particulate matter and gases; forest and prairie fires
can emit large quantities of "pollutants"; plants and trees naturally emit VOCs which are oxidized
and form aerosols that can cause a natural blue haze; and dust storms can create large amounts of
particulate matter. Wild animals in their natural habitat are also considered natural sources of
"pollution".
Air Pollution Effects: The presence of pollution in the atmosphere results directly in air quality
degradation. Air pollution is also a critical factor affecting the quality of other environmental
resources as well as the human-made structures and facilities in the area. Polluted air can and has
harmed park resources in a variety of ways depending upon the chemistry of the pollutant, weather
and environmental conditions, and the nature or sensitivity of resources. Examples of this harm
include vegetative discoloration and growth disruption from ozone, loss of aquatic species from
stream acidification, shifts in nutrient availability from acid deposition, and erosion of building
surfaces and rock formations. Air pollution impairs visibility and contributes to climate change.
Air pollution can also be detrimental to human health.
Major Air pollutants
3
