air pollution
DESCRIPTION
Air PollutionTRANSCRIPT
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Lecture 11
Air & Noise Pollution
Lecture 11
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The Atmosphere
- thin, gaseous envelope of air around Earth
- we live at the bottom of this sea of air
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The atmosphere is divided into the:
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Troposphere
- atmosphere’s inner layer
- contains most of Earth’s air
- N2 ( 78% ), O2 ( 21% ), CO2 ( 0.04% )
- weather occurs here
- temperature drops with an increase in altitude
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Stratosphere
- layer above troposphere
- temperature rises with altitude
- our global sunscreen
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Stratosphere cont’d
- contains O3 “good ozone”
- ozone layer prevents 99% of harmful ultraviolet radiation from reaching Earth’s surface
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Stratosphere cont’d
O3’s filtering action protects us from:
* increased sunburn
* skin & eye cancer
* cataracts
* damage to our immune system
* damage to aquatic and land organisms
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Ozone in the Troposphere(Pollutant)
Trace amounts of O3 that form in the troposphere as a component of urban smog cause damage to:
• plants
• materials, e.g., rubber
• respiratory systems of humans & other animals
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What is Air Pollution?
- one or more chemicals in high enough concentrations in the air to:
1) harm organisms or materials
2) alter climate
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Air Pollution
Excess heat and noise are also considered forms of air pollution.
Such chemicals or physical conditions are called air pollutants.
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Sources of Air Pollution
1. Natural events(e.g., volcanic eruptions, dust storms)
2. Human activities(e.g., emissions from cars and smoke stacks)
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Major Classes of Air Pollutants
1. Carbon Oxides
- e.g., CO & CO2
2. Sulfur Oxides
- e.g., sulfur dioxide (SO2), sulfur trioxide (SO3)
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Major Classes of Air Pollutants cont’d
3. Nitrogen Oxides
- e.g., nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O)
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Major Classes of Air Pollutants cont’d
4. Volatile Organic Compounds
- e.g., methane, propane, benzene, chlorofluorocarbons (CFCs)
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Major Classes of Air Pollutants cont’d
5. Suspended Particles
- e.g., solid particles (dust, asbestos, soot)
- e.g., liquid droplets (pesticides, sulfuric acid)
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Major Classes of Air Pollutants cont’d
6. Photochemical Oxidants
- e.g., ozone, hydrogen peroxide
7. Radioactive Substances
- e.g., radon-222, plutonium-239
8. Toxic Compounds
- e.g., trace amounts of at least 600 toxic substances, 60 of them are carcinogens
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Types of Air Pollutants
Primary Pollutant
- chemical, that occurs in a harmful concentration, added directly to the air by natural events or human activities
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Types of Air Pollutants cont’d
Secondary Pollutant
- harmful chemical formed in atmosphere when a primary air pollutant reacts with the normal air components or with other air pollutants
e.g.. ozone, sulphur trioxide
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Urban Air Pollution
Smog
- originally a combination of smoke & fog
- now describes other mixtures in the atmosphere
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Urban Air Pollution cont’d
Photochemical Smog
- mixture of primary & secondary pollutants
- formed when hydrocarbons and nitrogen
oxides react under the influence of sunlight.
- Dominated by ozone
- found in almost all modern cities
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Urban Air Pollution cont’d
Industrial Smog
- consists mainly of a mixture of sulfur dioxide, suspended droplets of sulfuric acid and a variety of suspended solid particles
- found in cities that burn large amounts of coal and heavy oil which contain sulfur impurities
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Effects of Climate & Topography on Air Pollution
• Areas with high average annual precipitation, help cleanse the air of pollutants.
• Winds help sweep pollutants away and bring in fresh air.
• Hills & mountains reduce the flow of air in valleys below and allow pollutant levels to build up at ground level.
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Effects of Climate & Topography on Air Pollution cont’d
• Buildings in cities slow wind speed & reduce dilution and removal of pollutants.
• The process of hot air rising and cold air sinking causing continual mixing of air, helps keep pollutants from reaching dangerous levels near the ground.
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Temperature Inversion
- also called thermal inversion
- layer of dense, cool air trapped under a layer of stagnant, less dense warm air
- in a prolonged inversion, air pollution in the trapped layer may build up to harmful levels
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THERMAL INVERSION
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Urban Heat Island
- build-up of heat in the atmosphere above an urban area
- heat is produced by the large concentrations of cars, buildings, factories and other heat-producing activities
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Dust Dome
- dome of heated air that surrounds an urban area and traps and keeps pollutants, especially suspended particulate matter
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Effects of Air Pollution
Air pollution damages:
° human health
° plants
° aquatic life
° materials
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Acid Deposition
- the falling of acids and acid-forming compounds from the atmosphere to the earth’s surface
- commonly known as acid rain
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Acid Rain
- refers only to wet deposition of droplets of acids and acid-forming compounds
- natural precipitation is slightly acidic (pH 5.0-5.6)
- acid rain can have a pH of 4.3 or 3 (as acidic as vinegar)
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Harmful Effects of Acid Deposition
- contributes to human respiratory diseases
- damages foliage and weaken trees
- contaminate fish
- damages statues, buildings, metals, & car finishes
- releases aluminium ions which damage tree roots
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Greenhouse Effect
- natural effect that traps heat in the troposphere
- some of the heat flowing back toward space from Earth’s surface is absorbed, by H2O vapour, CO2, O3 and other gases, then radiated back toward Earth’s surface
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Greenhouse Gases
- gases in the troposphere that cause the greenhouse effect
- include:
carbon dioxide
chlorofluorocarbons (CFCs)
ozone
methane
water vapour
nitrous oxide
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Greenhouse Gases cont‘d
- the 2 predominant greenhouse gases are:- water vapour- carbon dioxide
- if the atmospheric concentrations of these gases increase, the average temperature of the troposphere will gradually rise
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Global Warming
- warming of atmosphere due to increases in the concentrations of one or more greenhouse gases primarily as a result of human activities, mainly:
burning of fossil fuels
use of CFCs
agriculture
deforestation
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Global Warming cont’d
In recent decades certain greenhouse gases have increased in concentration:
carbon dioxidemethanenitrous oxide CFCs
CO2 contributes to ~ 55% of global warming.
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Global Warming cont’d
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Possible Impacts of Global Warming on Caribbean States
- disastrous for ecosystems
- alter climatic conditions faster than some species could adapt
- shift food-growing areas
- rise in sea levels may flood coastal settlements
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Possible Impacts of Global Warming on Caribbean States cont’d
- more frequent and fierce hurricanes
- disastrous for economic and social systems
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Ozone Layer
- layer of gaseous ozone that protects life on Earth by filtering out harmful ultraviolet radiation from the sun
- being depleted by CFCs, halons and other chemicals
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CFCs
- Chlorofluorocarbons
- used in air conditioners, refrigerators, aerosol spray cans, cleaners for electronic parts, hospital sterilants, fumigants, plastic foam
- ozone eaters
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Impact of Ozone Depletion
- increased cases of cancer & cataracts
- suppression of human immune system
- lowers crop yield
- degradation of materials
- reduction in phytoplankton
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Noise Pollution
- any unwanted, disturbing or harmful sound that impairs or interferes with hearing, causes stress, hampers concentration and work efficiency or causes accidents
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Impact of Noise Pollution
- permanent hearing loss
- hypertension
- insomnia
- irritability
- migraine headaches
- muscle tension
- gastric (stress) ulcers
- psychological disorders (eg, increased aggression)
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Solutions to Air & Noise Pollution
- enforce air & noise pollution laws
- use emission control devices
- ban or limit smoking to well-ventilated areas
- tax each unit of pollution produced
- use office machines in well-ventilated areas
- shift to less polluting energy sources
- increase intake of outdoor air
- car exhaust inspections