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Chemistry of the atmosphere (The Earth's early atmosphere (theories…
Chemistry of the atmosphere
The proportions of different gases in the atmosphere
for 200 million years proportions of different gases in the atmosphere have been much the same s they are today:
80% nitrogen
20% oxygen
small proportions of various other gases, including carbon dioxide, water vapour and noble gases
The Earth's early atmosphere
theories have changed and developed over time - evidence for the early atmosphere is limited because of the time scale of 4.6 billion years
one theory suggests that during the first billion years there was intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form oceans - as the start of this period the Earth's atmosphere may have been like the atmosphere of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas
volcanoes also produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia
when the oceans formed carbon dioxide in the water and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere
How oxygen increased
algae and plants produced the oxygen that is now in the atmosphere by photosynthesis
carbon dioxide + water --> glucose +oxygen
algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere. Over the next billion years plants evolved and the percentage of oxygen gradually increases to a level that enabled animals to evolve
Greenhouse gases
green house gases in the atmosphere maintain temperatures on Earth high enough to support life.
Water vapour
,
carbon dioxide
and
methane
are green house gases
Human activities which contribute to an increase in greenhouse gases in the atmosphere
carbon dioxide
and
methane
are added to atmosphere by humans
many scientists believe that human activities will cause the temperature of the Earth's atmosphere to increase at the surface and that this will result in global climate change
however it is difficult to model such complex systems as global climate change
Global climate change
an increase in average global temperatures is a major cause of climate change
there are several effects of global climate change
The carbon footprint and its reduction
cabon footprint is the total amount of carbon dioxide and other greenhouse gas emitted over the full life cycle of a product, service or event
the carbon footprint can be reduced by reducing emissions of carbon dioxide and methane
Atmospheric pollutants from fuels
the combustion of fuels is a major source of atmospheric pollutants
most fuels, including coal, contain carbon and/or hydrogen and may also contain some sulfur
the gases released into the atmosphere when s fuel id burned may include carbon dioxide,water vapour, carbon monoxide, sulphur dioxide and oxides of nitrogen. Solid particles and unburned hydrocarbons may also be released that from particulates in the atmosphere
Properties and effects of atmospheric pollutants
carbon monoxide is a toxic gas. It is colourless and odourless and so is not easily detected
sulfur dioxide and oxides of nitrogen cause respiratory problems in humans and cause acid rain
particulates cause global dimming and health problems for humans
How carbon dioxide decreased
algae and plants decreased the percentage in the atmosphere by photosynthesis
was also decreased by the formation of sedimentary rocks and fossil fuels that contained carbon