ESS Unit 6: Atmospheric Systems and Societies

Atmosphere

a dynamic system of inputs outputs storages and flows

Composition of the atmosphere

Nitrogen, Oxygen, CO2, argon, water vapor, and others.

Structure of the Atmosphere

• Troposphere

• Stratosphere

• Mesosphere

• Thermosphere

Troposphere (0-10 km above sea level)

• The layer closest to the earth’s surface

• Most of the atmospheric mass is found. Includes water vapour, clouds and pollutants. (Albedo Effect)

• Most of our weather occurs.

• The greenhouse effect occurs and helps to regulate the temperature of the earth.

Stratosphere ( 10 to 50km above sea level)

• absorbs and filters ultra violet radiation from the sun

• protection against meteorites.

Mesosphere (50 to 80km)

• Without the presence of ozone or other particulates to absorb UV radiation, the temperature declines with height.

• There are strong winds

• protection against meteorites.

Thermosphere (beyond about 80km)

• UV and X-radiation from the sun is absorbed which breaks apart molecules into atoms. Warmest atmospheric layer.

• Oxygen, nitrogen and helium atoms are the main components in the upper thermosphere

• The ionosphere is also located within the thermosphere and comprises of an area in which the particles are electrically charged.

Greenhouse Effect

The process by which certain gases in the Earth's atmosphere trap heat from the sun, leading to an increase in the Earth's temperature.

• essential for supporting life on Earth, helps to maintain a stable climate. Without it it would be too cold.

Human Enhanced Greenhouse Effect

The increase in the Earth's greenhouse effect caused by human activities, primarily the burning of fossil fuels and deforestation. This leads to an increase in greenhouse gases, such as carbon dioxide (CO2), in the atmosphere. These gases trap more heat from the sun, causing the Earth's temperature to rise, resulting in global warming and climate change.

Ozone

Molecule of 3 atoms. Found in stratosphere (good sign) and troposphere (bad sign).

Ozone Layer Function

a protective shield in the Earth's stratosphere, absorbing most of the sun's ultraviolet (UV) radiation.

• prevents the majority of harmful UV-B and UV-C rays from reaching the Earth's surface

How is the ozone formed

formed through a process called photodissociation. In the stratosphere, oxygen molecules (O2) are broken apart by high-energy ultraviolet (UV) radiation from the Sun. The resulting oxygen atoms (O) then combine with other oxygen molecules to form ozone (O3). This process is known as the ozone-oxygen cycle.

How is ozone destroyed

destroyed through chemical reactions involving chlorine and bromine atoms. These atoms are released into the atmosphere from ODS. When these chlorine and bromine atoms come into contact with ozone molecules, they break apart the ozone, leading to its destruction. This process is known as ozone depletion.

UV Radiation

Negative

• Genetic Mutations

• Cataracts

• Skin Cancer

Positive:

• Production of Vitamin D

• Treats skin diseases

• Used to sterilize water

Chlorofluorocarbons (CFCs)

• Long lifetimes

• Coolants in refrigerators and air conditioning systems, Propellants in aerosol cans, Cleaning agents for electrical parts, and Blowing agents in plastic foam.

• Not soluble

Effect of CFCs on ozone

Within the stratosphere, UV light breaks down the CFC molecule producing chlorine atoms that starts a chain reaction. The chlorine atoms react with ozone breaking it down and reforming chlorine atoms. This unsettles the previous ozone equilibrium, resulting in ozone depletion.

Ozone depleting substances (ODS)

• Methyl bromide (It releases bromine in the stratosphere that is estimated to be about 50 times more effective than chlorine at destroying ozone, soil fumigator to eradicate pests)

• Halons, similar to CFCs but with bromine (used as fire suppressants in fire extinguishers.)

• HBFCs (contain bromine and/or fluorine. They are used as solvents, cleaning agents and as suppressants in fire extinguishers).

• Carbon tetrachloride

• Methyl chloroform.

effects of ozone depletion

Ozone depletion refers to the thinning of the ozone layer in the Earth's stratosphere.

• Increased UV radiation: This can lead to increased risks of skin cancer, cataracts, and weakened immune systems in humans.

• Climate change: Ozone-depleting substances, such as chlorofluorocarbons (CFCs), are also potent greenhouse gases. Their release contributes to global warming and climate change.

Management of stratospheric ozone

an international environmental treaty that was designed to protect the ozone layer. It was agreed upon in 1987 and has been ratified by almost every country in the world (best ex. of international cooperation)

• aims to phase out the production and use of substances that deplete the ozone layer

• Some challenges faced are: lack of alternatives, Long life span of ODS, Replacement chemicals also ODS, Illegal trade, lack of legistation