Lecture 11

Air & Noise Pollution

Air Pollution – Specific Objectives

At the end of this lecture students should be able to:

1. Describe the five-layered structure of the atmosphere and the % composition of gases within it.

2. List and describe the six major types of air pollutants, distinguishing between primary and secondary air pollutants.

3. Explain the occurrence of urban smog and the impact of topography and climate on it.

4. List indoor sources of air pollution.

5. Describe the effect of air pollution on the ecosystem through acid deposition, global warming and ozone depletion.

6. Explain how air pollution can be mitigated.

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

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.

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

eg. ozone, sulphur trioxide

Sources of Air Pollution

1. Natural events(eg, volcanic eruptions, dust storms)

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

Major Classes of Air Pollutants

1. Carbon Oxides

- eg, CO & CO2

2. Sulfur Oxides

- eg, sulfur dioxide (SO2), sulfur trioxide (SO3)

Major Classes of Air Pollutants cont’d

3. Nitrogen Oxides

- eg, nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O)

Major Classes of Air Pollutants cont’d

4. Volatile Organic Compounds

- eg, methane, propane, benzene, chlorofluorocarbons (CFCs)

Major Classes of Air Pollutants cont’d

5. Suspended Particles

- eg, solid particles (dust, asbestos, soot)

- eg, liquid droplets (pesticides, sulfuric acid)

Major Classes of Air Pollutants cont’d

6. Photochemical Oxidants

- eg, ozone, hydrogen peroxide

7. Radioactive Substances

- eg, radon-222, plutonium-239

8. Toxic Compounds

- eg, trace amounts of at least 600 toxic substances, 60 of them are carcinogens

Urban Air Pollution

Smog

- originally a combination of smoke & fog

- now describes other mixtures in the atmosphere

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

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

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

- enhances harmful effects of urban heat islands and dust domes

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

Indoor Air Pollution

Sources of Indoor Pollution

1. Cigarette Smoke

- causes heart disease, lung & other cancers, bronchitis, stroke

- avoidable

- most preventable major cause of death and suffering among adults

The Effects of Cigarette Smoking

Normal Lung Smoke-Damaged Lung

Happy Smoker?

Sources of Indoor Pollution cont’d

2. Radioactive radon-222 gas

- produced when underground uranium in rock and soil decays and enters homes through cracks, drains and hollow concrete blocks

- colourless, odourless, tasteless

- naturally occurring radioactive gas

Sources of Indoor Pollution cont’d

3. Asbestos

- sprayed on ceilings and walls for soundproofing, fireproofing and insulation

- once used in brake linings

(replaced by aramid)

- can cause asbestiosis and cancers

Sources of Indoor Pollution cont’d

4. Formaldehyde

- colourless, irritating gas

- found in fingernail hardener, plywood, particleboard, paneling, drapes, upholstery, and fiberboard

- used in countertops, kitchen cabinets & 90% of US furniture

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

- kills fishes (prevents eggs hatching below pH 5)

- 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

ozone

methane

water vapour

nitrous oxide

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

- Global warming is expected to result in climate change. It is possible that there will be:

- 2-3 degree centigrade rise in temperature by 2080

- Decreased rainfall between June and August

- Sea level rise 0.2-0.5 metres by 2090

- Increased frequency and intensity of hurricanes

Possible Impacts of Global Warming/Climate Change on Caribbean States

- Warmer winters may result in less tourists

- Climatic conditions may change faster than some species could adapt resulting in extinction

- Food-growing areas may change

- It is estimated that a 2 degree centigrade rise in temperature will reduce output of some crops such as kidney beans by 14-20%.

Possible Impacts of Global Warming/Climate Change on Caribbean States

- There may be longer periods of drought

- Increased temperatures will cause coral bleaching

Rising sea levels may:

- flood coastal settlements- result in beach erosion- raise the salinity of low lying areas reducing

productivity

Possible Impacts of Global Warming on Caribbean States cont’d

- more frequent and fiercer hurricanes

- disastrous for economic and social systems

Ozone Depletion

- The ozone layer is a layer of gaseous ozone located in the stratosphere

- The stratosphere contains O3 “good ozone”

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

- It is being depleted by CFCs, halons and other chemicals

Ozone Depletion 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

CFCs

- Chlorofluorocarbons

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

- ozone eaters

- halons

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