Chemistry of the atmosphere
The evolution of the atmsphere
Phase 1- volcanoes erupt and release gases. Early atmosphere mostly carbon dioxide with not much oxygen. This is like Mars or Venus today. Volcanic activity releases nitrogen- built up in atmosphere overtime as well as water vapour, methane and ammonia.
Phase 2- water vapour condenses, forms oceans. Lots of carbon dioxide removed as it is dissolved in oceans- goes through a series of reactions to form carbon precipitates- form sediments on seabed. Green plants and algae evolved and absorb carbon dioxide so can photosynthesise. Marine animals then evolved. shells and skeletons contain carbonates from oceans. Organisms took in some carbon from atmosphere and oceans, which became locked up in rocks and fossil fuels after organisms died. When plants, plankton and marine animals die, fall into seabed and get buried by layers of sediment. Over millions of years, get compressed and form sedimentary rocks, oil and gas- trap carbon to reduce levels of carbon dioxide. Coal, crude oil and natural gas made by this process- formed fro deposits of plankton- form reservoirs under seabed when they get trapped in rocks.
Coal- sedimentary rock made from thick plant deposits. Limestone- sedimentary rock made of calcium carbonate deposits from shells and skeletons of marine organisms.
Phase 3- green plants absorb carbon dioxide and produce oxygen by photosynthesis. Algae evolved first- 2.2 billion years ago. Green plants evolved over next billion years. As oxygen levels build up, more complex life able to evolve.
200 million years ago, atmosphere reaches a composition similar to today- 80% N, 20% O2, and small amounts of other gases- mainly CO2, noble gases and water vapour.
Greenhouse gases and climate change
Greenhouse gases like carbon dioxide, methane and water vapour act like an insulating layer in the Earth's atmosphere- warms Earth to support life.
All particles absorb certain frequencies of radiation. Greenhouse gases only absorb long wavelength radiation that gets reflected back off the Earth- then re-radiated in all directions including back towards Earth. Long wave radiation is thermal radiation so results in warming the surface of the Earth- greenhouse effect.
Human activity affect amount of greenhouse gases in the atmosphere:
Deforestation- fewer trees, less carbon dioxide removed.
Burning fossil fuels- locked up carbon released as carbon dioxide.
Agriculture- more farm animals produce methane through digestive processes.
Creating waste- more landfill sites and waste from agriculture means more carbon dioxide and methane released by decomposition of waste.
Recently, Earth's surface has been increasing- due to human activity which will lead to climate change. Evidence from scientists; peer-reviewed (other scientists check and give explanations; reliability). The Earth's climate is so complex that it is hard to understand- so many variables. Led to speculation by media; biased stories.
Predictions about consequences of climate change:
Polar ice caps melting- rise in sea levels, increase in flooding and coastal erosion.
Changes in rainfall patterns- regions get too much/less water. Change in temperature and ability to produce food.
Frequency and severity of storms may increase.
Change in temperature and amount of water available in a habitat may affect wild species leading to differences in distribution.
Carbon footprint
Carbon footprint- measure of the amount of carbon dioxide and other greenhouse gases released over a full life cycle of something.
Can be difficult to measure as there are different factors to consider.
Can reduce carbon footprint by:
Renewable energy resources/ nuclear energy instead of fossil fuels.
Use more efficient processes to conserve energy and cut waste.
Tax people on how much greenhouse gases they emit.
Government can put a cap on emissions- then sell licences up to that cap.
Technology that captures carbon dioxide produced by burning of fossil fuels before released into atmosphere- can be stored underground e.g. old oil wells.
Making reductions can be difficult because:
Alternative energies need to be studied and worked on.
changes may have an impact on economic growth- affect wellbeing.
Difficult to make international agreements to reduce emissions.
Countries do not want to change lifestyles as well as people.
Air pollution
Fossil fuels contain hydrocarbons. During combustion, the carbon and hydrogen are oxidised so carbon dioxide and water vapour are released into atmosphere- complete combustion as plenty of oxygen when fuel burns.
If not enough oxygen; incomplete combustion and solid particles (particulates) of soot and unburnt fuels released and carbon monoxide produced- if particulates are inhaled, get stuck to lungs and cause damage; respiratory problems. Bad for the environment as causes global dimming- reflect sunlight back into space so less light reaches Earth.
Carbon monoxide stops the blood from carrying oxygen in the body. It binds into haemoglobin in the blood that carries oxygen so less oxygen is transported. May cause fainting, coma, death. It doesn't have colour or smell, hard to detect- dangerous.
Sulfur dioxide released during combustion of fossil fuels (coal) that contains sulfur impurities- Sulfur becomes oxidised. Nitrogen oxides created from reaction between nitrogen and oxygen in air caused by heat of burning (internal combustion of cars)- when it mixes with clouds; forms dilute sulfuric acid or dilute nitric acid- falls as acid rain and kills plants, damages buildings and corrodes metals. Sulfur dioxide and nitrogen oxide can be bad for human health- cause respiratory problems if breathed in.