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Unit 2 mod 3 Atmosphere page 1 of 11THE ATMOSPHERE

Layers of Atmosphere

Earth's atmosphere can be divided into five main layers. These layers are mainlydetermined by whether temperature increases or decreases with altitude. From

highest to lowest, these layers are:

Troposphere

The troposphere begins at the surface and extends to between 7 km (23,000 ft) at

the poles and 17 km (56,000 ft) at the equator, with some variation due to

weather. The lowest part of the troposphere is warmest and temperature

decreases with altitude. The tropopause is the boundary between the troposphere

and stratosphere.

Stratosphere

The stratosphere extends from the tropopause to about 51 km (32 mi;

170,000 ft). Temperature increases with height, which restricts turbulence and

mixing. Thestratopause, which is the boundary between the stratosphere and

mesosphere.

Mesosphere

The mesosphere extends from the stratopause to 8085 km (5053 mi; 260,000

280,000 ft). It is the layer where mostmeteors burn up upon entering the

atmosphere. Temperature decreases with height in the mesosphere.

Thermosphere

Temperature increases with height in the thermosphere from the mesopause up

to the thermopause, then is constant with height. The top of the thermosphere is

the bottom of the exosphere, called the exobase.

Exosphere

The outermost layer of Earth's atmosphere extends from the exobase upward.

Here the particles are so far apart that they can travel hundreds of km without

colliding with one another.

http://en.wikipedia.org/wiki/Tropospherehttp://en.wikipedia.org/wiki/Tropopausehttp://en.wikipedia.org/wiki/Stratospherehttp://en.wikipedia.org/wiki/Stratopausehttp://en.wikipedia.org/wiki/Stratopausehttp://en.wikipedia.org/wiki/Stratopausehttp://en.wikipedia.org/wiki/Mesospherehttp://en.wikipedia.org/wiki/Meteorhttp://en.wikipedia.org/wiki/Meteorhttp://en.wikipedia.org/wiki/Thermospherehttp://en.wikipedia.org/wiki/Thermopausehttp://en.wikipedia.org/wiki/Exobasehttp://en.wikipedia.org/wiki/Exospherehttp://en.wikipedia.org/wiki/Tropospherehttp://en.wikipedia.org/wiki/Tropopausehttp://en.wikipedia.org/wiki/Stratospherehttp://en.wikipedia.org/wiki/Stratopausehttp://en.wikipedia.org/wiki/Mesospherehttp://en.wikipedia.org/wiki/Meteorhttp://en.wikipedia.org/wiki/Thermospherehttp://en.wikipedia.org/wiki/Thermopausehttp://en.wikipedia.org/wiki/Exobasehttp://en.wikipedia.org/wiki/Exosphere

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Unit 2 mod 3 Atmosphere page 2 of 11Maintenance of ozone concentration in stratosphere

Ozone is produced by uv radiation which is plentiful in the stratosphere.

These four equations are the Chapman reactions which regulate the

concentration of ozone in the stratosphere. Note that hv represents

uv light.

(1) Photodissociation causes the oxygen molecule to dissociate, (2) each oxygen

atom then can combine with an oxygen molecule to form ozone.(3) Ozone molecules dissociate when in contact with uv rays reforming an

oxygen molecule and oxygen atom. (4) An ozone molecule and oxygen atom

combine to form 2 oxygen molecules.

Significance of CFCs in ozone layer

CFCs and other contributory substances are commonly referred to asozone-depleting substances (ODS). Since the ozone layer prevents most

harmful UVB wavelengths (270315 nm) ofultraviolet light (UV light)from passing through the Earth's atmosphere, observed and projected

decreases in ozone have generated worldwide concern leading to

adoption of theMontreal Protocol that bans the production of CFCs andhalons (halogenoalkane) as well as related ozone depleting chemicals

such as carbon tetrachlorideandtrichloroethane. It is suspected that avariety of biological consequences such as increases in skin cancer,

cataracts, damage to plants, and reduction ofplanktonpopulations in the

ocean'sphotic zone may result from the increased UV exposure due toozone depletion. Ozone is also a very powerful oxidising agent.

CFCs are non-toxic, low boiling, inert compounds and thus diffuse to the

stratosphere where it undergoes fission by uv light. An example of the

reactions are shown below

Step 1 CFCl3 + h CFCl2 + ClStep 2 Cl + O3 ClO + O2Step 3 ClO + O3 Cl + 2 O2

Steps 2 and 3 result in a chain reaction. Essentially CFCs result in the

destruction of the ozone layer. One chlorine atom can destroy 100,000

ozone molecules.

http://en.wikipedia.org/wiki/Ultraviolethttp://en.wikipedia.org/wiki/Ultraviolethttp://en.wikipedia.org/wiki/Earth's_atmospherehttp://en.wikipedia.org/wiki/Montreal_Protocolhttp://en.wikipedia.org/wiki/Montreal_Protocolhttp://en.wikipedia.org/wiki/Carbon_tetrachloridehttp://en.wikipedia.org/wiki/Carbon_tetrachloridehttp://en.wikipedia.org/wiki/1,1,1-Trichloroethanehttp://en.wikipedia.org/wiki/1,1,1-Trichloroethanehttp://en.wikipedia.org/wiki/1,1,1-Trichloroethanehttp://en.wikipedia.org/wiki/Skin_cancerhttp://en.wikipedia.org/wiki/Skin_cancerhttp://en.wikipedia.org/wiki/Cataractshttp://en.wikipedia.org/wiki/Cataractshttp://en.wikipedia.org/wiki/Planktonhttp://en.wikipedia.org/wiki/Planktonhttp://en.wikipedia.org/wiki/Photic_zonehttp://en.wikipedia.org/wiki/Ultraviolethttp://en.wikipedia.org/wiki/Earth's_atmospherehttp://en.wikipedia.org/wiki/Montreal_Protocolhttp://en.wikipedia.org/wiki/Carbon_tetrachloridehttp://en.wikipedia.org/wiki/1,1,1-Trichloroethanehttp://en.wikipedia.org/wiki/Skin_cancerhttp://en.wikipedia.org/wiki/Cataractshttp://en.wikipedia.org/wiki/Planktonhttp://en.wikipedia.org/wiki/Photic_zone

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Effects of ozone on human lifea) Stratospheric ozone

Although the concentration of the ozone in the ozone layer is very small, it isvitally important to life because it absorbs biologically harmful ultraviolet (UV)

radiation coming from the Sun. UV radiation is divided into three categories,

based on its wavelength; these are referred to as UV-A (400315 nm), UV-B

(315280 nm), and UV-C (280100 nm). UV-C, which would be very harmful

to humans, is entirely screened out by ozone at around 35 km altitude. UV-B

radiation can be harmful to the skin and is the main cause ofsunburn; excessive

exposure can also cause genetic damage, resulting in problems such as skin

cancer. The ozone layer screens out 95% of UV-B; for radiation with a

wavelength of 290 nm, the intensity at the top of the atmosphere is 350 milliontimes stronger than at the Earth's surface.

b) Tropospheric ozoneThe majority of tropospheric ozone formation occurs when nitrogen oxides

(NOx), carbon monoxide (CO) andvolatile organic compounds(VOCs), such as

xylene, react in the atmosphere in the presence of sunlight. NOx, CO, and VOCs

are called ozone precursors. Motor vehicle exhaust, industrial emissions, andchemical solvents are the major anthropogenic (man-made) sources of these

chemicals.

Ozone is known to have the following health effects at concentrations common

in urban air:

Irritation of the respiratory system, causing coughing, throat irritation,

and/or an uncomfortable sensation in the chest.

Reduced lung function, making it more difficult to breathe deeply andvigorously. Breathing may become more rapid and more shallow than

normal, and a person's ability to engage in vigorous activities may be

limited.

Aggravation ofasthma. When ozone levels are high, more people with

asthma have attacks that require a doctor's attention or use of

medication. One reason this happens is that ozone makes people more

sensitive to allergens, which in turn trigger asthma attacks.

Increased susceptibility to respiratory infections. Inflammation and damage the lining of the lungs. Within a few days,

the damaged cells are shed and replaced much like the skin peels after a

sunburn. Animal studies suggest that if this type of inflammation

happens repeatedly over a long time period (months, years, a lifetime),

lung tissue may become permanently scarred, resulting in permanent

loss of lung function and a lower quality of life.

http://en.wikipedia.org/wiki/Sunburnhttp://en.wikipedia.org/wiki/Skin_cancerhttp://en.wikipedia.org/wiki/Skin_cancerhttp://en.wikipedia.org/wiki/Nitrogen_oxideshttp://en.wikipedia.org/wiki/Carbon_monoxidehttp://en.wikipedia.org/wiki/Volatile_organic_compoundshttp://en.wikipedia.org/wiki/Volatile_organic_compoundshttp://en.wikipedia.org/wiki/Volatile_organic_compoundshttp://en.wikipedia.org/wiki/Xylenehttp://en.wikipedia.org/wiki/Respiratory_systemhttp://en.wikipedia.org/wiki/Lunghttp://en.wikipedia.org/wiki/Asthmahttp://en.wikipedia.org/wiki/Allergenhttp://en.wikipedia.org/wiki/Upper_respiratory_tract_infectionhttp://en.wikipedia.org/wiki/Sunburnhttp://en.wikipedia.org/wiki/Skin_cancerhttp://en.wikipedia.org/wiki/Skin_cancerhttp://en.wikipedia.org/wiki/Nitrogen_oxideshttp://en.wikipedia.org/wiki/Carbon_monoxidehttp://en.wikipedia.org/wiki/Volatile_organic_compoundshttp://en.wikipedia.org/wiki/Xylenehttp://en.wikipedia.org/wiki/Respiratory_systemhttp://en.wikipedia.org/wiki/Lunghttp://en.wikipedia.org/wiki/Asthmahttp://en.wikipedia.org/wiki/Allergenhttp://en.wikipedia.org/wiki/Upper_respiratory_tract_infection

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Checkpoint A

Importance of carbon cycle

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The element carbon is necessary for all organic material. Its presence is

maintained by the carbon cycle. On the previous page shows the variousprocesses involved in the carbon cycle.

If all the carbon was present in the atmosphere as CO2, the greenhouseeffect would be enhanced to such a level, that life as we know it on Earthwould cease to exist. If all the carbon was locked in the sediments

(rocks) or vegetation or animals, again life would cease as no morephotosynthesis would be able to occur and life would swiftly end.

In recent times, the balance of carbon has been disrupted by the extreme

levels of fossil fuel combustion, causing a dramatic increase in the level

of CO2 in the atmosphere. CO2 is a greenhouse gas and an increase in its

levels causes an increase in the mean temperature of the Earth. This has

undesirable effects on weather patterns and countries climates.

In order to remove the excess carbon dioxide in the atmosphere, a

concept such as carbon sequestering can be used. Carbon sequesteringis a geoengineeringtechnique for long-term storage ofcarbon dioxide or

other forms ofcarbon to mitigate global warming. Carbon dioxide isusually captured from the atmosphere through biological, chemical or

physical processes.

Biological:- Reforestation i.e. the replanting of trees on marginal crop

and pasture lands

http://en.wikipedia.org/wiki/Geoengineeringhttp://en.wikipedia.org/wiki/Geoengineeringhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Mitigation_of_global_warminghttp://en.wikipedia.org/wiki/Geoengineeringhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Mitigation_of_global_warming

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Unit 2 mod 3 Atmosphere page 6 of 11Physical:- Biomass burial i.e. burying trees which are now dead whichresulting in a mimicking of the natural process of fossil fuel formation

Chemical:- Mineral sequestration i.e. the reaction of carbon dioxide witheither magnesium oxide or calcium oxide to form the respective

carbonates.

The greenhouse effect

The greenhouse effect is a process by w

hich radiative energy leaving a

planetary surface is absorbed by some atmospheric gases, called

greenhouse gases. They transfer heat to other components of the

atmosphere, and also re-radiate energy in all directions, including backdown towards the surface. This transfers energy to the surface and lower

atmosphere, so the temperature there is higher than it would be if direct

heating by solar radiation were the only warming mechanism.

Higher levels of CO2 in present time (around 380ppm) causes anenhanced greenhouse effect which results in an increase of the average

temperature of the Earth than in the past with lower levels of CO2

(315ppm)

Causes of global warming

High levels of combustion of fossil fuels releasing CO2

High amounts of methane gas from grazing animals and landfills

Release of nitrous oxide from fertilisers

Release of refrigerants for industrial processes

Deforestation whether man-made or natural via the burning of forestsin dry seasons

Effects of global warming

Sea levels to rise

http://en.wikipedia.org/wiki/Sea_level_risehttp://en.wikipedia.org/wiki/Sea_level_rise

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Change the amount and pattern ofprecipitation, probably including

expansion ofsubtropical deserts

Continuing retreat of glaciers,permafrost and sea ice.

Other likely effects include changes in the frequency and intensity ofextreme weatherevents, species extinctions, and changes in

agricultural yields.

Warming and related changes will vary from region to region around

the globe, though the nature of these regional variations is uncertain.

Photochemical smog

Photochemical smog is the chemical react

ion of sunlight, nitrogen oxides

(NOx) and volatile organic compounds (VOCs) in the atmosphere, which

leaves airborne particles (calledparticulate matter) and ground-levelozone.

Nitrogen oxides are released by nitrogen and oxygen in the air reacting together

under high temperature such as in the exhaust offossil fuel-burning engines in

cars, trucks,coalpower plants, and industrial manufacturing factories. VOCs are

released from man-made sources such as gasoline(petrol),paints, solvents,

pesticides, and biogenic sources, such as pine and citrus tree emissions.

Effects of photochemical smog

It can inflame breathing passages, decrease the lungs' working

capacity, cause shortness of breath, pain when inhaling deeply,

wheezing, and coughing.

It can cause eye and nose irritation and it dries out the protective

membranes of the nose and throat and interferes with the body's

ability to fight infection, increasing susceptibility to illness.

Checkpoint B

http://en.wikipedia.org/wiki/Precipitation_(meteorology)http://en.wikipedia.org/wiki/Subtropicshttp://en.wikipedia.org/wiki/Deserthttp://en.wikipedia.org/wiki/Retreat_of_glaciers_since_1850http://en.wikipedia.org/wiki/Permafrosthttp://en.wikipedia.org/wiki/Sea_icehttp://en.wikipedia.org/wiki/Extreme_weatherhttp://en.wikipedia.org/wiki/Extreme_weatherhttp://en.wikipedia.org/wiki/Extinction_risk_from_climate_changehttp://en.wikipedia.org/wiki/Agricultural_yieldhttp://en.wikipedia.org/wiki/Nitrogen_oxideshttp://en.wikipedia.org/wiki/Volatile_organic_compoundhttp://en.wikipedia.org/wiki/Particulate_matterhttp://en.wikipedia.org/wiki/Tropospheric_ozonehttp://en.wikipedia.org/wiki/Tropospheric_ozonehttp://en.wikipedia.org/wiki/Tropospheric_ozonehttp://en.wikipedia.org/wiki/Fossil_fuelhttp://en.wikipedia.org/wiki/Fossil_fuelhttp://en.wikipedia.org/wiki/Automobilehttp://en.wikipedia.org/wiki/Coalhttp://en.wikipedia.org/wiki/Coalhttp://en.wikipedia.org/wiki/Coalhttp://en.wikipedia.org/wiki/Power_planthttp://en.wikipedia.org/wiki/Gasolinehttp://en.wikipedia.org/wiki/Gasolinehttp://en.wikipedia.org/wiki/Painthttp://en.wikipedia.org/wiki/Solventhttp://en.wikipedia.org/wiki/Pesticidehttp://en.wikipedia.org/wiki/Pesticidehttp://en.wikipedia.org/wiki/Precipitation_(meteorology)http://en.wikipedia.org/wiki/Subtropicshttp://en.wikipedia.org/wiki/Deserthttp://en.wikipedia.org/wiki/Retreat_of_glaciers_since_1850http://en.wikipedia.org/wiki/Permafrosthttp://en.wikipedia.org/wiki/Sea_icehttp://en.wikipedia.org/wiki/Extreme_weatherhttp://en.wikipedia.org/wiki/Extinction_risk_from_climate_changehttp://en.wikipedia.org/wiki/Agricultural_yieldhttp://en.wikipedia.org/wiki/Nitrogen_oxideshttp://en.wikipedia.org/wiki/Volatile_organic_compoundhttp://en.wikipedia.org/wiki/Particulate_matterhttp://en.wikipedia.org/wiki/Tropospheric_ozonehttp://en.wikipedia.org/wiki/Tropospheric_ozonehttp://en.wikipedia.org/wiki/Fossil_fuelhttp://en.wikipedia.org/wiki/Automobilehttp://en.wikipedia.org/wiki/Coalhttp://en.wikipedia.org/wiki/Power_planthttp://en.wikipedia.org/wiki/Gasolinehttp://en.wikipedia.org/wiki/Painthttp://en.wikipedia.org/wiki/Solventhttp://en.wikipedia.org/wiki/Pesticide

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Effects of combustion of hydrocarbon based fuels

Pollutants Source/how

produced

Effects

carbon

dioxide

burning of oil, coal

and natural gas

Increase of carbon dioxide in the

atmosphere leads to the

"greenhouse effect".When the energy from the sun is

reflected back from the earth, thegas prevents this energy from

returning to outer space andultimately causes temperatures on

Earth to rise, similar to agreenhouse.

sulphur

dioxide

burning of oil, coal

or gasolinecontaining sulphur

the gas is absorbed in rain water

which causes the formation of acidrain.acid rain destroys vegetation and

damages marble and limestone

buildings.

carbonmonoxide

incomplete burningof fossil fuels

poisonous, prevents uptake ofoxygen by haemoglobin.

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Unit 2 mod 3 Atmosphere page 9 of 11increases the formation of carbondioxide i.e. enhancing the

greenhouse effect

Oxides ofnitrogen

Internalcombustion engine,reaction of nitrogen

gas with oxygengas

Same as for sulphur dioxide

Leadcompounds

Leaded gasolinespecifically

tetraethyl lead

Forms volatile lead compounds orelemental lead. Lead acts as a

cumulative poison and it can cause

madness and then deathCFCs Petro-chemical

industry, aerosol

propellants

Forms radicals in the ozone layerwhich ultimately destroys the

ozone layer. This can cause anincreased incidence of skin

cancers.

NOx concentration in the atmosphereNOx is produced in the atmosphere by a variety of ways.

Via lightning high temperature causes the reaction of nitrogen gas and

oxygen gas to form nitrogen monoxide

In the internal combustion engine, the high temperature causes the

nitrogen and oxygen gases to react to form NOxOnce NOx is in the atmosphere, their concentrations can be affected by

precipitation resulting in acid rain. That is the reaction of NOx and waterforming dilute solutions of nitric acid.

The formation of acid rain, the Haber Process and use of fertilisers also

affects the nitrogen cycle, the amount of nitrates present in the soil.

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Methods of control and prevention of atmospheric pollutionPollutant Method of control

Particulate For large particles:- Baghouses or similar

equipment are used which utilise centrifugal forcesto create a cyclone to trap particles and collect

them, removing them from the air flow

For small particles:- Electrostatic precipitators are

used, these exploit the fact that particles areusually charged and by passing dirty air through

charged plates, the particles are attracted to the

oppositely charged plate and the air comes out

clean

Gases Scrubbers (wet)

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Unit 2 mod 3 Atmosphere page 11 of 11A wet scrubber uses an anti parallel flow of wateragainst the flow of gas (gas travelling upward and

water flowing downward). Note the water is in

very fine droplets to increase surface area. Thepollutant then dissolves or reacts with the water,allowing the air to become clean.

Prevention of atmospheric pollution

Use of alternative fuels (purely electric cars)

Improved technology (improved catalytic converters, hybri

d cars (use

of electricity and gasoline for propulsion)

Mass transit (car pooling, use of public transportation) (although thecars or vehicles would still cause pollution)

Checkpoint C