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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 heatproducing 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
Happy Smoker?
Smoke-Damaged
Lung
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 5.05.6)
- 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 dioxide
methane
nitrous 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