Air Pollution

transcript

Lecture 11

Air & Noise Pollution

Lecture 11

The Atmosphere

- thin, gaseous envelope of air around Earth

- we live at the bottom of this sea of air

The atmosphere is divided into the:

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

Stratosphere

- layer above troposphere

- temperature rises with altitude

- our global sunscreen

Stratosphere cont’d

- contains O3 “good ozone”

- ozone layer prevents 99% of harmful ultraviolet radiation from reaching Earth’s surface

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

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

What is Air Pollution?

- one or more chemicals in high enough concentrations in the air to:

1) harm organisms or materials

2) alter climate

Air Pollution

Excess heat and noise are also considered forms of air pollution.

Such chemicals or physical conditions are called air pollutants.

Sources of Air Pollution

1. Natural events(e.g., volcanic eruptions, dust storms)

2. Human activities(e.g., emissions from cars and smoke stacks)

Major Classes of Air Pollutants

1. Carbon Oxides

- e.g., CO & CO2

2. Sulfur Oxides

- e.g., sulfur dioxide (SO2), sulfur trioxide (SO3)

Major Classes of Air Pollutants cont’d

3. Nitrogen Oxides

- e.g., nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O)

4. Volatile Organic Compounds

- e.g., methane, propane, benzene, chlorofluorocarbons (CFCs)

5. Suspended Particles

- e.g., solid particles (dust, asbestos, soot)

- e.g., liquid droplets (pesticides, sulfuric acid)

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

Types of Air Pollutants

Primary Pollutant

- chemical, that occurs in a harmful concentration, added directly to the air by natural events or human activities

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

Urban Air Pollution

- originally a combination of smoke & fog

- now describes other mixtures in the atmosphere

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

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

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.

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.

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

THERMAL INVERSION

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

Dust Dome

- dome of heated air that surrounds an urban area and traps and keeps pollutants, especially suspended particulate matter

Indoor Air Pollution

Effects of Air Pollution

Air pollution damages:

° human health

° plants

° aquatic life

° materials

Acid Deposition

- the falling of acids and acid-forming compounds from the atmosphere to the earth’s surface

- commonly known as acid rain

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)

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

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

Greenhouse Gases

- gases in the troposphere that cause the greenhouse effect

- include:

carbon dioxide

chlorofluorocarbons (CFCs)

methane

water vapour

nitrous oxide

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

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

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.

Global Warming cont’d

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

Possible Impacts of Global Warming on Caribbean States cont’d

- more frequent and fierce hurricanes

- disastrous for economic and social systems

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

- Chlorofluorocarbons

- used in air conditioners, refrigerators, aerosol spray cans, cleaners for electronic parts, hospital sterilants, fumigants, plastic foam

- ozone eaters

Impact of Ozone Depletion

- increased cases of cancer & cataracts

- suppression of human immune system

- lowers crop yield

- degradation of materials

- reduction in phytoplankton

Noise Pollution

- any unwanted, disturbing or harmful sound that impairs or interferes with hearing, causes stress, hampers concentration and work efficiency or causes accidents

Impact of Noise Pollution

- permanent hearing loss

- hypertension

- insomnia

- irritability

- migraine headaches

- muscle tension

- gastric (stress) ulcers

- psychological disorders (eg, increased aggression)

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

Air Pollution

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