The document discusses the evolution of Earth's atmosphere over time from early volcanic activity releasing gases like carbon dioxide and methane to the development of oxygen and current atmospheric composition. It also covers air pollution sources like burning fossil fuels, the impacts of carbon dioxide, sulfur dioxide, and particulates, and methods to reduce pollution like removing sulfur from fuels, wet scrubbing, catalytic converters, and alternative energy sources.

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Air QualityAir Quality
W Richards
The Weald School
(OCR 21st
Century)

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Section C1.1 – Our airSection C1.1 – Our air

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The Earth’s AtmosphereThe Earth’s Atmosphere
Carbon dioxide, water vapour Oxygen Nitrogen Noble gases
Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble
gases and about 0.03% CO2

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AirAir
Air is a mixture of different gases consisting of small
molecules with large spaces between them:

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4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the EarthEvolution of the Earth’’s Atmospheres Atmosphere
Carbon
dioxide
Methane Ammonia Oxygen Nitrogen Others
Present day
atmosphere contains
78% nitrogen, 21%
oxygen, 1% noble
gases and about
0.03% CO2

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4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the EarthEvolution of the Earth’’s Atmospheres Atmosphere
Volcanic activity
releases CO2, methane,
ammonia and water
vapour into the
atmosphere. The water
vapour condenses to
form oceans.
Some of the oxygen is
converted into ozone.
The ozone layer blocks
out harmful ultra-violet
rays which allows for the
development of new life.
Green plants evolve which take in CO2 and
give out oxygen. Carbon from CO2
becomes locked up in sedimentary rocks as
carbonates and fossil fuels. Methane and
ammonia react with the oxygen and
nitrogen is released.

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Carbon dioxide in the atmosphereCarbon dioxide in the atmosphere
The amount of CO2 in the atmosphere is affected by 3 things:
1) Geological activity moves carbonate rocks deep into
the Earth and they release ______ _______ into the
atmosphere during volcanic activity.
2) When fossil fuels are burned the carbon
contained in them reacts with _____ to form CO2.
3) Increased CO2 in the atmosphere causes a reaction
between it and _______. These reactions do not remove ALL
of the new CO2 so the greenhouse effect is still getting
_______!
Words – oxygen, seawater, carbon dioxide, worse

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PollutionPollution
What happens to pollution?
Carbon dioxide causes global warming but some
of it can be removed by plants (photosynthesis)
or reactions with seawater.
Sulfur dioxide and nitrogen
dioxide cause acid rain which
damages trees and buildings.
Particulates (like in smog) can make buildings
dirty and worsen breathing difficulties.

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PollutionPollution
Humans pollute the Earth in a number of ways:
Pollutant Harmful to... Why?
Carbon dioxide Environment
Nitrogen oxides Environment +
humans
Sulfur dioxide Environment
Particulates (e.g.
Smoke)
Environment +
humans
Carbon monoxide Humans
A greenhouse gas that causes
global warming
Causes acid rain and makes
asthma/breathing problems worse
Causes acid rain
Makes buildings dirty and makes
asthma worse
Displaces oxygen in red blood cells
that can result in death

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Section C1.2 – PollutionSection C1.2 – Pollution

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FuelsFuels
Fuels are substances that can be used to release useful
amounts of energy when they burn, e.g.
Oil GasWood Coal
These fuels are called “fossil fuels” and
are described as being “non-renewable”.
The main element in these fuels is Carbon.

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Burning HydrocarbonsBurning Hydrocarbons
Burning hydrocarbons will produce water, carbon dioxide and
energy:
C
H
H
H
H
O
O
O
O
OH H
OH H
C
O
O
Methane Oxygen+ Water+Carbon
dioxide
In this reaction the hydrocarbon is “oxidised” (“oxidised”
means that oxygen has been added and it’s the opposite of
reduced).
Oil, petrol and diesel are all examples of
HYDROCARBONS. A hydrocarbon is a compound
made up of carbon and hydrogen.

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More information on oxygenMore information on oxygen
Fuels need oxygen to burn. The more
oxygen they have, the quicker they will
burn. This is the principle behind oxy-
acetylene torches:

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Other products of burning fuelsOther products of burning fuels
Sulphur dioxide:
Nitrogen monoxide:
Nitrogen monoxide can
be further oxidised to
make nitrogen dioxide
(Nitrogen monoxide and
dioxide are jointly
referred to as NOx):
S
O
O
Sulphur
dioxide
S
O
O
Sulphur Oxygen+
Nitrogen
monoxide
N
O
N
O
Oxygen+
O
O
Nitrogen
N
N
O
O
Oxygen+
Nitrogen
monoxide
N
O
N
O
Nitrogen
dioxide
N OO
N OO

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Conservation of mass in reactionsConservation of mass in reactions
In any reaction the total mass of products is
the same as the total mass of the reactants
Example 1 – Magnesium oxide and hydrochloric acid
Mg
O
H Cl
Mg Cl
Cl
H
H
OH Cl
1 x magnesium, 1 x oxygen, 2 x
hydrogen and 2 x chlorine atoms
Also 1 x magnesium, 1 x oxygen, 2
x hydrogen and 2 x chlorine atoms
C
H
H
H
H
O
O
O
O
OH H
OH H
C
O
O
Example 2 – Burning methane

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Incomplete CombustionIncomplete Combustion
As well as producing carbon monoxide, incomplete combustion
can also produce soot:
Little
oxygen:
CC
H
H
H
H
Methane
O
O
Oxygen+
OH H
OH H
Water+Carbon
“Soot”

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Burning Fossil FuelsBurning Fossil Fuels
Burning fossil fuels like oil and coal causes pollution.
Oil contains carbon:
C
H
H
H
H
O
O
O
O
OH H
OH H
C
O
O
Carbon dioxide is a “greenhouse
gas” – it helps cause global warming
Coal contains carbon, sulfur and other particles:
sulfur + oxygen sulfur dioxide
Sulfur dioxide causes acid rain. Other particles can
cause “global dimming” – sunlight is absorbed by the
particles in the atmosphere.

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Summary of pollutantsSummary of pollutants
C
Carbon
C
O
O
Carbon
dioxide
Nitrogen
monoxide
N
O
Nitrogen
dioxide
O N
O
S
O
O
Sulfur
dioxide
OH H
Water
C
Carbon
monoxide
O
Each of the following chemicals is a product of burning fossil
fuels. For each one summarise how it is made and what harm it
causes:

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C1.3 Improving Air QualityC1.3 Improving Air Quality

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Removing PollutionRemoving Pollution
There are many ways pollution can be reduced:
• Use less electricity/central heating
• Remove toxic chemicals before or
after they are burnt
• Use alternative energy sources, e.g.
wind power

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Removing SulfurRemoving Sulfur
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Sulfur dioxide is clearly bad for the environment so it’s a good
idea to remove as much sulfur as possible:
Vehicles can remove sulfur
from fuels before they
are burned.
Power stations can remove sulfur dioxide from waste
gases after combustion.

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Wet ScrubbingWet Scrubbing
“Wet scrubbing” is a term used to describe
the removal of sulfur dioxide and other
particles using seawater or an alkaline spray:
Step 1 – the dirty gas
is fed in through the
top.
Step 2 – the
“scrubbing liquid”
(seawater or
alkaline spray) is
fed in through
the side.
Step 3 – the
mixture is fed
into a cyclone
area where the
slurry is collected
at the bottom of
the device.

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Reducing Pollution from vehiclesReducing Pollution from vehicles
A number of suggestions:
1) Buy a new, smaller, more efficient car
2) Use legal limits (e.g. An MOT)
to enforce lower emissions
3) Use low sulfur fuels or convert your car to
run on biodiesel
4) Make sure your car has a catalytic converter:
5) Use the train or a bus!
Carbon monoxide + oxygen carbon dioxide
Nitrogen monoxide + carbon monoxide nitrogen + carbon monoxide

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Alternative FuelsAlternative Fuels
Car makers are currently researching two alternatives for
petrol and diesel-powered cars. What are the advantages and
disadvantages of each?
1) Electric cars
Advantages:
Disadvantages:
2) Biofuel cars
Advantages:
Disadvantages:

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Making choices about pollutionMaking choices about pollution
Choices concerning fighting pollution can be made on many
levels:
1) International
e.g. The Kyoto protocol in 1997
2) National
e.g. Car tax system, subsidies for greener technology
3) Local
e.g. Recycling schemes, transport,
congestion charges
4) Personal
e.g. Recycling, individual travel, reducing energy usage
in the home etc