Photochemical Smog (6.3)
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Resources:Topic 6: NotesREVIEW: JEOPARDY BOARD |
What is Air Pollution?
Air pollution is contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere.
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Primary Pollutants
Primary Pollutants
Atmospheric Primary Pollutants |
Major Primary Pollutants:
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Dangers of Particulates:
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Secondary Pollutants
Secondary Pollutants
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Tropospheric Ozone
Secondary Pollutant
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Effects of Tropospheric Ozone:
- Ozone is a toxic gas and oxidizing agent when in troposphere.
- Ground Level Ozone causes:
- Damage to plants – ozone is absorbed by plants but it degrades chlorophyll, so productivity is reduced
- Damage to humans- at low concentrations, photochemical smog reduces action of the lungs causing breathing to become difficult
- Damage to materials and products:
- Attacks natural rubber, cellulose, and some plastics
- Reduces the lifetime of car tires
- Bleaches fabrics
Formation of Photochemical Smog
Smog has been known to cause major respiratory issues for people. In the early 1900s, it resulted in deaths of many people until the Clean Air Acts were enacted.
Smog chemical composition:
What Causes Photochemical Smog |
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Main primary pollutants reach maximum in the morning and evening rush hours, and smog is maximized in the early afternoon.
Effects of Smog:
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Thermal Inversion
Thermal Inversion within a city makes smog worse. Air on the surface of the earth is warmer in general and as it rises cools. An inversion happens naturally when the air is unable to be recycled due to high pressure systems pushing down on the cooler air. When you add photochemical smog to a normal inversion:
Causes and Consequences of Thermal Inversion |
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Air Quality Health Standards
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National Ambient Air Quality Standards
These are the specific measurements of pollutants that you can be exposed to in a specific time period for it to be considered hazardous to different groups. Primary and Secondary groups are defined below:
Note that length and exposure amount can change depending on group. Although generally considered to be the same for secondary and primary.
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Pollution Management Strategies
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Pollution management strategies for photochemical smog include trying to reduce the amount of fossil fuels burned, increasing public use of public transport/ walking/ biking. Regulation and taxation of the use of anything causing Sulfur dioxide or nitric oxides is generally around things like requiring catalytic converters in cars, regulating fuel quality etc. Restoration is more difficult, but can include Re-greening cities by building parks and repurposing old parking lots of run down buildings to help absorb carbon. It can also include large outdoor city air filters.
EPA pollutants criteria |