Passed in 1970 to specify the 6 air pollutants that the EPA (Environmental Protection Agency) monitors/limits
These six pollutants are sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), particulate matter (PM), tropospheric ozone (O3), and lead (Pb)
Carbon dioxide (CO2) is not listed in the Clean Air Act
Although carbon dioxide is a greenhouse gas, it doesn’t directly lower air quality for humans, and it isn’t directly toxic/damaging
The EPA’s regulation of the use of lead significantly reduced the amount of lead in the atmosphere
Coal combustion
The process of burning coal in order to produce energy
This releases CO, CO2, SO2, NOx, toxic metals, and particulate matter
SO2, or sulfur dioxide, is a respiratory irritant that can threaten those with asthma and bronchitis
The sulfurous aerosols and the smog caused by its release can block the sun, which reduces visibility and photosynthesis
Forms when there is sunlight and heat/smoke from cars and factories
Typically, O3 forms during the day because of the presence of sunlight, but at night, it reacts with NO to transform back into O2
However, because VOCs (volatile organic compounds) react with NO to form photochemical oxidants, there is no longer enough NO in the atmosphere to react with/transform O3 back into O2 during the night
Therefore, the excess O3 in the atmosphere is able to combine with photochemical oxidants to form photochemical smog
Volatile organic compounds (VOCs)
These can be emitted from manmade buildings/services such as gas stations
When VOCs contribute to the formation of photochemical smog, they threaten human health by allowing for more respiratory irritants
Increased O3 can also block the sun from supporting photosynthesis
This occurs when cool air is trapped under a layer of warm air
Normally, the warmest layer of air is the one closest to the surface, and cooler air is able to travel away from land because it only has even cooler air above it
This is because warm air rises
Urban heat island effect
This happens when manmade surfaces in urban areas, such as concrete/asphalt, absorb a lot more heat than a vegetated area would
Because more heat is being stored, urban areas may be too warm
While hot urban surfaces are able to cool during nighttime, infrared radiation that was absorbed during the day is still being released
This creates a warm layer of air above the cool air
Pollutants in the cool air are trapped under the layer of warm air, which means that these pollutants are stuck in the atmosphere
The increased amount of pollutants in cities with thermal inversion can lead to respiratory illnesses, decreased tourism revenue, and increased smog
7.4 Atmospheric CO2 and Particulates
Carbon dioxide
Carbon dioxide can naturally occur as a result of cellular respiration, decomposition, and volcanic eruptions
Volcanic eruptions can also naturally release particulate matter
Forest fires can naturally release carbon dioxide and water vapor, which may act as greenhouse gases
Aerobic decomposition (done in the presence of oxygen) releases carbon dioxide
Anaerobic decomposition (done in low/no-oxygen areas) can release CH4 (methane)
Smaller particles can more easily enter the respiratory tract and can cause inflammation/irritation
7.5 Indoor Air Pollutants
Commercial fuels
Fuels supplied by utilities
Developed nations are more likely to use these (coal/oil/natural gas)
Indoor air pollutants in developed nations often result from chemicals in modern products such as insulation, lead paint, cleaning supplies, and adhesives in furniture
Dust and mold can also act as indoor air pollutants
Asbestos
Material once commonly used in insulation for houses
If the insulation is disturbed, then the asbestos can be released and could cause respiratory irritation
Carbon monoxide
Caused by incomplete combustion, which can happen as a result of a malfunctioning furnace ventilation
CO (carbon monoxide) can result in suffocation because the CO particles will prevent O2 from binding to hemoglobin in blood
Sound at levels high enough to cause physiological stress and hearing loss
In urban areas, noise pollution can be caused by activities like transportation, construction, and domestic/industrial activity
Noise pollution can harm animals in ecological systems by creating stress, masking sounds that are needed for communication/hunting, damaging hearing, and causing changes to migratory routes
Migratory routes might be affected if animals adjust their routes to avoid areas that are prone to noise pollution and its resulting stress/confusion
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AP Environmental Science Unit 7: Atmospheric Pollution
Passed in 1970 to specify the 6 air pollutants that the EPA (Environmental Protection Agency) monitors/limits
These six pollutants are sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), particulate matter (PM), tropospheric ozone (O3), and lead (Pb)
Carbon dioxide (CO2) is not listed in the Clean Air Act
Although carbon dioxide is a greenhouse gas, it doesn’t directly lower air quality for humans, and it isn’t directly toxic/damaging
The EPA’s regulation of the use of lead significantly reduced the amount of lead in the atmosphere
Coal combustion
The process of burning coal in order to produce energy
This releases CO, CO2, SO2, NOx, toxic metals, and particulate matter
SO2, or sulfur dioxide, is a respiratory irritant that can threaten those with asthma and bronchitis
The sulfurous aerosols and the smog caused by its release can block the sun, which reduces visibility and photosynthesis
Forms when there is sunlight and heat/smoke from cars and factories
Typically, O3 forms during the day because of the presence of sunlight, but at night, it reacts with NO to transform back into O2
However, because VOCs (volatile organic compounds) react with NO to form photochemical oxidants, there is no longer enough NO in the atmosphere to react with/transform O3 back into O2 during the night
Therefore, the excess O3 in the atmosphere is able to combine with photochemical oxidants to form photochemical smog
Volatile organic compounds (VOCs)
These can be emitted from manmade buildings/services such as gas stations
When VOCs contribute to the formation of photochemical smog, they threaten human health by allowing for more respiratory irritants
Increased O3 can also block the sun from supporting photosynthesis
This occurs when cool air is trapped under a layer of warm air
Normally, the warmest layer of air is the one closest to the surface, and cooler air is able to travel away from land because it only has even cooler air above it
This is because warm air rises
Urban heat island effect
This happens when manmade surfaces in urban areas, such as concrete/asphalt, absorb a lot more heat than a vegetated area would
Because more heat is being stored, urban areas may be too warm
While hot urban surfaces are able to cool during nighttime, infrared radiation that was absorbed during the day is still being released
This creates a warm layer of air above the cool air
Pollutants in the cool air are trapped under the layer of warm air, which means that these pollutants are stuck in the atmosphere
The increased amount of pollutants in cities with thermal inversion can lead to respiratory illnesses, decreased tourism revenue, and increased smog
7.4 Atmospheric CO2 and Particulates
Carbon dioxide
Carbon dioxide can naturally occur as a result of cellular respiration, decomposition, and volcanic eruptions
Volcanic eruptions can also naturally release particulate matter
Forest fires can naturally release carbon dioxide and water vapor, which may act as greenhouse gases
Aerobic decomposition (done in the presence of oxygen) releases carbon dioxide
Anaerobic decomposition (done in low/no-oxygen areas) can release CH4 (methane)
Smaller particles can more easily enter the respiratory tract and can cause inflammation/irritation
7.5 Indoor Air Pollutants
Commercial fuels
Fuels supplied by utilities
Developed nations are more likely to use these (coal/oil/natural gas)
Indoor air pollutants in developed nations often result from chemicals in modern products such as insulation, lead paint, cleaning supplies, and adhesives in furniture
Dust and mold can also act as indoor air pollutants
Asbestos
Material once commonly used in insulation for houses
If the insulation is disturbed, then the asbestos can be released and could cause respiratory irritation
Carbon monoxide
Caused by incomplete combustion, which can happen as a result of a malfunctioning furnace ventilation
CO (carbon monoxide) can result in suffocation because the CO particles will prevent O2 from binding to hemoglobin in blood
Sound at levels high enough to cause physiological stress and hearing loss
In urban areas, noise pollution can be caused by activities like transportation, construction, and domestic/industrial activity
Noise pollution can harm animals in ecological systems by creating stress, masking sounds that are needed for communication/hunting, damaging hearing, and causing changes to migratory routes
Migratory routes might be affected if animals adjust their routes to avoid areas that are prone to noise pollution and its resulting stress/confusion
