IB ESS Unit 6

The Atmosphere and its Functions

The layers of gases surrounding the Earth. Its atmosphere is composed of ~78% nitrogen, ~21% oxygen, and one percent other gases.

• It provides a shield from meteorites.

• It protects us from harmful radiation from the sun.

• It moderates and stabilizes our climate including temperature.

• It is from where we obtain the oxygen we breathe and from where plants acquire the carbon dioxide they require for photosynthesis.

Layers of the atmosphere

Closest to Earth:

Troposphere: Where all the weather patterns happen, temperatures decrease

Stratosphere: Ozone layer takes place here, temperatures increase here

Mesosphere: temperatures decrease with altitude

Thermosphere: absorbs ultraviolet radiations, so temperatures increase

Exosphere: gradually translates to outer space, the last layer.

Furthest away from Earth

Greenhouse effect

Without GHG’s the heat is radiated back into space, resulting in average global temperatures of -18 C

With GHG’s, long wave radiation is absorbed by gases, resulting in warming of the atmosphere to average temperatures of 15 C. This is the natural greenhouse effect.

We see that increasing the GHG’s in atmosphere results in an unnatural enhanced greenhouse effect, warming the planet.

Albedo Effect

the ability of surfaces to reflect sunlight. linked to how white the surface is. clouds reflect and absorb a lot of solar energy and also trap heat below them depending on how thick and high they are

Air Circulation and the Corilis effect

• Rising air: warm and moist, low-density, low-pressure area

• Falling air: cool and dry, high density and high-pressure area

Corilis Effect → Because of the spin of the earth, objects – air currents, water and current deflect makes storm swirl clockwise in the southern hemisphere and counterclockwise in the Northern Hemisphere

Ozone & its formation cycle

Ozone is a replenishable, colourless, unstable toxic gas with powerful oxidising properties. The ozone layer is found in the stratosphere and shields us from much of the sun's ultraviolet radiation.

Ozone Cycle → When UV rays hit ozone (O₃), the molecule separates into an ozone radical (O) and Oxygen (O₂). The radical ozone continues to travel around until it hits Oxygen again, combining back into Ozone

Chlorofluorocarbon Compounds (CFCs) - uses, benefits & disadvantages

CFCs → nontoxic, nonflammable chemicals containing atoms of carbon, chlorine, and fluorine.

Used as coolants (refrigerators), propellants (hairsprays and deodorants), fumigants (bug spray), etc.

Benefits:

• chemically stable

• nontoxic

• odourless

• nonflammable

• noncorrosive

Disadvantages:

• discovered to be lowering the concentration of stratospheric ozone (more UV getting through)

  • UV radiation splits chlorine atoms from CFCs which combines with radical ozones, depleting the concentration of ozone

Impacts of UV rays and management strategies

Impacts:

• Worse sunburns

• More eye cataracts and skin cancers

• Immune system suppression

• Damage to producers (like plants and phytoplankton) due to sensitivity, affecting entire ecosystems.

• Reduced yield for sensitive crops

Management Strategies:

• Replace

  • use eco-friendly spray and coolant products instead of CFCs - this is hard without bans/fines

  • education and campaigning (EPA Clean Air Act)

• Regulate

  • Montreal Protocol (1980s) - an agreement originally signed by 24 countries (now 197 after 2000s) to regulate the production and consumption of CFCs

  • Started after a hole in the ozone layer was discovered over the Antarctic, reaching a peak size of 30 million square kilometres

  • by the 2000s, CFCs had been reduced by 30%

  • As of December 2024, the size of the ozone hole is 21.9 million km²

• Restore

  • Despite research, no technologies have been implemented to restore the ozone hole

Formation of photochemical smog

1. Pollutants are released: nitrogen oxides [NOx] and volatile organic compounds [VOCs])

2. Sunlight hits them → causes chemical reactions

3. These reactions produce ozone (O₃) in the troposphere

4. In addition to ozone, the reactions also produce Nitrogen dioxide (NO₂), Peroxyacyl nitrates (PANs), Aldehydes & Fine particles

5. The mixture of these chemicals and ozone form photochemical smog

Thermal Inversions

a layer in the atmosphere in which air temperature increases with height.

Factors effecting smog formation

• Topography → valley creates thermal inversions to trap smog

• Population Density → More people, more pollution

• Fuels types → used for industry, transportation and heating homes

• Local climate → reductions by rain & snow cleansing the air or wind transporting pollution elsewhere

Pollution Management

• Reduce

  • Decrease demand for electricity/fossil fuels by switching to renewable energy

  • Alter human activity → public transport, walking, biking, etc.

• Regulate

  • Government regulation/taxation (carbon tax)

  • using catalytic converters to clean the exhaust of primary pollutants from car exhaust

• Restore

  • adopting clean-up measures such as reforestation, regreening, and conservation

Acid Deposition and its sources

any form of precipitation with acidic components that fall to the ground from the atmosphere in wet or dry forms.

Sources:

• coal burning power plants

• smelters

• cars

• industrial plants

Types of acid deposition

Starting materials → Sulfur Dioxide (SO₂) and Nitrogen Dioxide (NO₂)

• Wet deposition

  • SO₂ and NO₂ mix with water in the atmosphere to form nitric acid and sulfuric acid. it falls as rain, snow, vapour or fog and lasts 4-14 days

• Dry deposition

  • Converted into particulate compunds as sulfates and nitrates. they last 2-3 days and falls near the emission source

Impacts of acid rain on plants, water/aquatic organisms and humans

Plants:

• weakens tree growth (disturbs root growth & function)

• lowers concentration of chlorophyll

• breaks down lipids

• needles shed more often

Water/Aquatic Organisms:

• low biodiversity

• kills indicator species

• improved visibility

• increased dissolved metals (zinc, lead, aluminium, etc.)

Humans:

• respiratory diseases (bronchitis & asthma)

• leach toxic materials (lead & copper) from pipes into drinking water

• damages infrastructure

• decreases atmospheric visibility

Management Strategies for Acid deposition

• Replace

  • replace private vehicles with public transport, bikes & walking

  • switch to low sulfur fuels

  • use more renewable energy

• Regulate

  • but caps on fossil fuels and offer subsidies for using renewable energy

• Restoration

  • liming lakes - adding limestone (reduce acidification)