Topic 6: Atmospheric systems & societies - ESS

The gaseous composition of the Earth’s atmosphere

78% nitrogen

21% oxygen

0.04% carbon dioxide

0.96% other gases

Atmospheric layers (lowest to highest)

• Troposphere (cloud formation, precipitation, mixing of gases)

• Stratosphere (Ozone layer)

• Mesophere

• Thermosphere

Storages in the atmosphere

The atmosphere stores greenhouse gases such as carbon dioxide and methane which contribute to the greenhouse effect and influence the Earth’s temperature

Flows in the atmosphere

Air currents, weather patterns, atmospheric circulation all contribute to the movement and redistribution of gases and other substances within the atmosphere

Inputs into the atmosphere

Natural inputs: volcanic eruptions, gaseous emissions, dust particles

Anthropogenic inputs: release of GHGs, pollutants from industrial processes, aerosols from combustion

Outputs from the atmosphere

Respiration and photosynthesis release gas, precipitation and dry deposition remove pollutants and aerosols from the atmosphere

How the composition of the atmosphere changed through geological time

During early Earth, the atmosphere had high levels of carbon dioxide and lacked oxygen. Over millions of years, photosynthetic organisms evolved and released oxygen, oxygenating the atmosphere. Additionally, volcanic activity and meteorite impacts have influenced the atmospheric composition.

Where do clouds form and why?

Majority of clouds form in the troposphere. This happens as an increase altitude results in a decreased temperature, creating conditions favourable for the cooling and condensation of water vapour.

Albedo effect of clouds

Clouds have high albedo (high reflectivity of solar radiation), reflecting a significant amount of sunlight back into space. This in turn cools the Earth’s surface, lowering the amount of energy absorbed by the planet, offsetting the warming effects from greenhouse gases.

Factors that change cloud cover + its effects

Aerosol pollution, changes in atmospheric circulation patterns, and climate change all influence cloud formation and distribution

Effects of ozone depleting substances on the atmosphere and ecosystems

Ozone-depleting substances, such as CFCs, pesticides, and refrigerants reduces the amount of atmospheric ozone. This increases UV radiation and its ability to reach the Earth’s surface, harming photosynthetic organisms and humans.

Effects of carbon dioxide on the atmosphere and ecosystems

The burning of fossil fuels, deforestation, and other industrial processes all increase atmospheric carbon dioxide all enhance the greenhouse effect. This increases global warming and climate change, which has significant consequences on ecosystems and biodiversity.

Effects of water vapour on the atmosphere and ecosystems

Atmospheric water vapour concentrations are altered due to land use changes and agricultural and industrial processes. This results in changed precipitation patterns, causing droughts or extreme rainfall in certain regions, which impacts ecosystems, agriculture, and water availability.

Effects of methane on the atmosphere and ecosystems

Atmospheric methane increases due to agriculture, fossil fuel extraction and use, and waste management. This increase enhances the greenhouse effect, contributing to global warming and climate change. Increased methane also risks higher melting of the permafrost and ice caps causing a sea level rise.

Effects of nitrous oxide on the atmosphere and ecosystems

Increased atmospheric nitrous oxide levels are due to agriculture, combustion processes (in cars), and industrial activities. This increase affects air quality and contributes to global warming and climate change.

Effects of aerosols on the atmosphere and ecosystems

Aerosols are produced by industrial processes. They alter radiative properties of the atmosphere, affect air quality, and influence cloud formation and precipitation patterns. They impact human health and atmospheric sulfur dioxide and nitrogen oxides lead to acid rain formation.

What is the greenhouse effect?

It’s a naturally occurring phenomenon that involves greenhouse gases trapping the thermal energy emitted from the Sun in order to keep Earth at a temperature that can sustain life.

Interaction between the ozone layer and UV radiation.

Ozone (O₃) absorbs UV radiation and breaks apart into an oxygen molecule (O₂) and a free oxygen atom (O). This naturally occurs in the stratosphere. Under normal conditions, a free oxygen atom (O) will bind to another oxygen molecule (O₂) to form ozone (O₃).

Examples of ozone-depleting substances

• Aerosols - used in sprays and deodorants

• Pesticides - used for agriculture purposes

• Flame retardants - reduce flammability

• Refrigerants - used in air conditioners, fridges

UV radiation effects on humans and cells

• Cataracts - blurred vision / loss of vision

• Skin cancer

• Sunburn

• Premature skin ageing

Effects of UV radiation on biological productivity

• Damages photosynthetic organisms which reduces photosynthetic activity and growth which decreases primary productivity in aquatic ecosystems

• Overall disruption in ecosystem dynamics and stability

Ways to reduce ozone depletion

• Recycle refrigerants

• Developing alternatives to ODSs

  • Soap bars instead of shaving foam

  • Organic pest control instead of methyl bromide

  • Fridges that use propane

The role of UNEP in protecting the stratospheric ozone layer

The Montreal Protocol (1987) - reduced use of ozone depleting surfaces. Emissions of ODSs have rapidly fallen from 1.5 million tonnes in 1987 to 400,000 tonnes in 2010.

Differentiate between primary and secondary pollutants.

Primary pollutants are directly emitted from sources, whilst secondary pollutants are formed from when primary pollutants undergo chemical reactions in the presence of sunlight.

Examples of primary pollutants

• Carbon monoxide - harmful to human health

• Carbon dioxide - global warming and climate change contributor

• Black carbon / soot

• Nitrogen dioxide and nitrogen oxide - air pollutant that cause respiratory issues and form smog

• Sulfur dioxide and sulfur trioxide - cause acid rain and respiratory issues

Examples of secondary pollutants

• Tropospheric ozone - when oxygen molecules react with oxygen atoms released from nitrogen dioxide = cause respiratory issues and form smog

• Nitrogen oxides - contribute to acid rain and particulate matter pollution

The harmful effects of tropospheric ozone

• Damages plant tissues, reduces photosynthesis, reduces crop yields, and causes leaf damage

• Irritates the respiratory system and contributes to asthma

• Irritates the eyes

• Degradates rubber and causes cracking and discolouration of materials

Why are the impacts of tropospheric ozone widespread?

Tropospheric ozone can be transported by wind and risks significant damage to vegetation, human health, and materials.

Ways to mitigate tropospheric ozone

Implement air quality regulations, promote clean technologies, adopt sustainable practices

What is smog?

A type of air pollution that is comprised of both primary and secondary pollutants. Mostly made up of tropospheric ozone as well as particulate matter and other pollutants.

Factors influencing smog occurance

• Local topography

• Climate conditions

• Population density

• Fossil fuel use

• Hot and sunny climates are more susceptible to smog formation

• Certain geographical features that inhibit air movement, such as valleys or basins

How do thermal inversions contribute to smog formation?

Thermal inversions occur when a layer of cool, dense air is trapped under a layer of warm, less dense air. These conditions prevent the vertical mixing of air, making the pollutants accumulate near the ground. This trapped layer causes a persistent formation of smog, especially when the area experiences stable atmospheric conditions.

Economic losses due to urban air pollution

• Healthcare costs - poor air quality increases respiratory and cardiovascular diseases = higher healthcare costs = strains healthcare systems

• Decreased worker productivity - exposure to polluted air causes allergies and fatigue, which can decrease work performance = increased economic losses

• Loss of workdays - severe pollution makes people stay at home more, taking sick leave and reduced work hours leads to economic losses

• Environmental damage - contaminated air harms crops and vegetation, reducing agricultural yields = economic losses for industries reliant on agriculture, forestry, and tourism

• Decreased property values - areas with high levels of air pollution experience a decline in property values = negative economic consequences for homeowners and real estate people

Air pollution management strategies: altering human activity

Encourage the use of energy-efficient technologies, promote the use of public transport, and encourage walking or cycling for shorter distances

Air pollution management strategies: regulating and reducing pollutants at point of emission

Government regulations that set emission limits and standards, impose taxes or fees on high-polluting activities, promote renewable energy

Air pollution management strategies: catalytic converters

Catalytic converters are installed in vehicles’ exhaust systems to reduce emissions of primary pollutants. They facilitate chemical reactions to convert harmful pollutants into less harmful substances.

Air pollution management strategies: regulate fuel quality

Governments can establish fuel quality standards so they contain fewer pollutants. E.g. implement stricter controls on sulfur content in fuels to reduce sulfur dioxide emissions.

Air pollution management strategies: adopting clean-up measures

• Reforestation - creates more carbon sinks and mitigates greenhouse gas effect

• Re-greening - creation of green spaces improves air quality and creates shaded, cool areas

• Conservation of natural areas - maintain carbon sequestration and reduces air pollution

What is acid deposition?

When fossil fuels combust, it releases sulfur dioxide and nitrogen oxides are released into the atmosphere. They undergo chemical reactions and transform into secondary pollutants and are deposited as either dry or wet particles.

Causes of primary pollutants

• Power plants that burn fossil fuels contribute to sulfur dioxide emissions (SO₂) - they directly form acid rain

• Vehicle exhausts release nitrogen oxides (NO_x)

How are secondary pollutants formed?

Sulfur dioxide and nitrogen oxides undergo chemical reactions with compounds that are already present in the atmosphere (e.g. oxygen and water vapour). This reaction forms sulfuric acid and nitric acid.

Dry deposition of secondary pollutants

Sulfuric acid and nitric acid combine with ash and form dry particles. These particles will eventually settle on surfaces such as vegetation, buildings, and soil which will damage them over time.

Wet deposition of secondary pollution

Sulfuric acid and nitric acid can dissolve in rainwater or snowflakes, forming acidic precipitation. These particles fall to the ground and affect surface water and soils.

Direct effects of acid deposition

• Reacts with metals and rocks and cause buildings to corrode and weaken.

• Lowers the pH of the water, making it difficult for species to survive and reproduce.

• Causes leaf damage, blocks stomata from exchanging gases.

Indirect effects of acid deposition

• Increases solubility of metals like aluminium, which is toxic

• Increases leaching of nutrients, reducing nutrient availability

How do geographic and transboundary impacts alter the impacts of acid deposition

Areas downwind of major industrial regions are more likely to experience more significant effects of acid deposition. These regions can surpass national boundaries, affecting areas in different countries.

Acid deposition management strategies: altering human activity

• Reduce consumption of fossil fuels

• Encourage development of renewable energy and clean technologies

• Utilise international agreements to promote sustainable practices

Acid deposition management strategies: regulating and monitoring pollutant release

• Implement government regulations to control and reduce release of pollutants

• Install pollution control devices such as scrubbers and catalytic converters

Acid deposition management strategies: clean-up and restoration measures

• Spread ground limestone to neutralise acidity and restore water pH

• Recolonisation efforts to restore damaged ecosystems

Limitations of clean-up and restoration measures for acid deposition

Applying limestone is expensive and their scope is limited. Prevention through emission reduction is more effective and sustainable.