Chemistry of the Atmosphere

• In the first billion years of the earth, its surface was covered in volcanoes which erupted and released lots of gases.

  The early atmosphere formed via these gases.

  Early atmosphere was made up of mostly carbon dioxide and virtually no oxygen.

  Volcanic activity released nitrogen, which built up in the atmosphere over time, as well as water vapour and small amounts of methane and ammonia.
• When the water vapour condensed, it formed the oceans.

  Lots of carbon dioxide was removed from the early atmosphere as it dissolved in the oceans.

  The dissolved carbon dioxide went through a series of reactions to form carbonate precipitates which formed sediments on the seabed.

  Marine animals evolved and their shells and skeletons contained some of these carbonates from the oceans.

  Green plants and algae evolved and absorbed some of this carbon dioxide to carry out photosynthesis.
• Carbon can become trapped in fossil fuels and rocks.

  When plants, plankton and marine animals die, they become compressed and form sedimentary rocks, oil and gas.

  The carbon is trapped within them.

  Coal, crude oil and natural gas are formed this way.
• Crude oil and natural gas are formed from deposits of plankton.

  Fossil fuels form reservoirs under the seabed.
• Coal is a sedimentary rock made from thick plant deposits.
• Limestone is a sedimentary rock.

  Its mostly made from the calcium carbonate deposits from the shells and skeletons of marine organisms.
• Green algae and plants produced oxygen via photosynthesis.

  Algae evolved about 2.7 billion years ago.

  Green plants also evolved over the next billion years.

  As oxygen levels built up, more complex life could evolve.
• About 200 million years ago, the atmosphere reached a similar composition of that of today.

  80% Nitrogen

  20% Oxygen

  Carbon Dioxide, Noble Gases and water vapour make up less than 1%.
• Greenhouse gases form an insulating layer in the earth's atmosphere.

  They absorb incoming long wave radiation reflected from the earth and do not absorb short wave radiation coming from the sun.

  They re-radiate the radiation in all directions.

  Longwave radiation is thermal radiation.
• Human activity can increase the amount of greenhouse gases in the atmosphere.

  Deforestation- Less CO2 is removed via photosynthesis.

  Burning Fossil Fuels releases CO2.

  Agriculture- More farm animals produces more methane.

  Creating Waste- More landfill sites and more waste from agriculture means more CO2 and Methane released by the decomposition of waste.
• Earth's temperature has varied naturally.

  The average temperature of the Earth has recently been increasing by a larger amount than what we would expect naturally.

  Most scientists agree that CO2 released from human activity is increasing global warming which leads to climate change.
• It is hard to fully understand the Earth's climate as it is so complex and has so many variables.

  However, evidence for climate change has been peer-reviewed which makes it more reliable.

  This has led to speculation between carbon dioxide and climate change.
• Polar ice caps can melt which increases sea levels- leading to increasing flooding and coastal erosion.

  Change in rainfall patterns can cause some regions to get too much or too little water. This can affect their ability to produce food.

  The frequency and severity of storms can increase.

  Changes in temperature and the amount of water available in a habitat may affect the distribution of wild species.
• It is very difficult to measure carbon footprints.

  Carbon footprints are a measure of the amount of carbon dioxide and other greenhouse gases released over the full lifecycle of something.

  When measuring carbon footprint, there are many factors to consider.

  You can make a rough calculation of the worst emitters.

  You can reduce carbon footprint.
• Renewable energy sources or nuclear energy sources can be used instead of fossil fuels.

  Using more efficient processes can conserve energy and cut waste.

  Lots of waste decomposes to release methane so will reduce methane emissions.

  Governments can tax companies or individuals based off the amount of greenhouse gases they emit.

  Governments can put a cap on emissions and sell licences for emissions up to that cap.

  Technology can capture CO2 and store in deep underground.
• Reductions to emission is difficult.

  Carbon capture and storage is a new idea at the development stage

  Renewable energy technologies are expensive and can be unreliable.

  A lot of governments are worried about the effect of cutting emissions on economic growth.

  It is hard to make international agreements to reduce emissions.
• Individuals can reduce their carbon footprint.

  They can choose to cycle or walk instead of using a car.

  They can reduce the amount they fly.

  They can save energy at home.

  It can be hard to get people to make changes in their lives.
• Combustion of fossil fuels releases gases and particulates.
• Hydrocarbons are oxidised and produce carbon dioxide and water in an abundance of oxygen- complete combustion.

  In incomplete combustion, solid particles made up of soot and unburned hydrocarbons are released as well as carbon monoxide which can be produced as well as carbon dioxide.
• Particulates can cause respiratory problems.

  They can reflect sunlight from the earth, causing global dimming.
• Carbon monoxide can stop the blood from carrying oxygen around the body.

  It binds to the haemoglobin that normally carries oxygen so less oxygen is carried around your body.

  A lack of oxygen in the blood can lead to fainting, a coma or even death.

  Carbon monoxide is tasteless, odourless and invisible.
• Sulfur Dioxide is produced in the combustion of fossil fuels that contain sulfur impurities which are oxidised to produce sulfur dioxide.

  Nitrogen oxides are produced when nitrogen reacts with oxygen in the air, caused by the heat of burning.
• Nitrogen oxide and sulfur dioxide can mix with water in the air to form dilute nitric/sulfuric acid which can fall as acid rain.

  Acid rain damages buildings and plants and makes metal corrode.

  Sulfur dioxide and nitrogen oxides can cause respiratory problems.