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topic 9-chemistry of the atmosphere (the evolution of the atmosphere…
topic 9-chemistry of the atmosphere
the evolution of the atmosphere
phase 1- volcanoes produced gases
the earths surface was covered in volcanoes which gave out gases
similar atmosphere to venus or mars
mostly carbon dioxide
released nitrogen, water vapour, ammonia and methane as well
phase 2- oceans, plants absorbed carbon dioxide
when water vapour condensed oceans were formed
lots of carbon dioxide dissolved in oceans, series of reactions to form carbonate precipitates that formed sedimentary rock
green plants and algae evolved and absorbed carbon dioxide for photosynthesis
later marine animals evolved and their shells and skeletons contained carbonate from the oceans
some of the carbon these organisms took in from atmosphere became locked up in rocks and fossil fuels after organisms died
when plants, marine animals die they fall to seabed where they are compressed as they are buried under layers of sediment, over millions of years form oil and gas trapping carbon in them
crude oil and natural gas are formed from deposits of plankton
coal is formed from thick plant deposits (a sedimentary rock)
phase 3- green plants produce oxygen
in photosynthesis plants produce oxygen as a waste product
algae evolved first (2.7 bil ago) then green plants (bil ago)
as oxygen levels increased more complex life evolved (animals)
today: 80% nitrogen, 20% oxygen, 1% other gases
greenhouse gases and climate change
carbon dioxide
greenhouse gases act like insulating layer in Earth's atmosphere- allows earth to be warm enough to support life
all particles absorb radiation, greenhouse gases absorb long wavelength radiation reflected back off the earth, then they reradiate it in all directions (including back at earth) the longwave radiation is thermal radiation so it warms the earth (greenhouse)
ways humans increase amount of greenhouse gases:
-deforestation: fewer trees means less CO2 absorbed for photosynthesis
-burning fossil fuels: carbon that is locked up in fuels is released
-agriculture: more farm animals means more methane produced through their digestive processes
-creating waste: more landfill sites means more CO2 and methane released by decomposition
increasing CO2 is linked to climate change
average temp of the earth Is increasing, scientists believe it is caused by human activity will lead to climate change
earths climate is hard to understand because there are lots of variables, complex, hard to model
this has led to speculation - biased stories
could have dangerous consequences
ice caps melting- rise in sea levels and flooding
change in rainfall patterns, too much or not enough water- may effect ability to produce food
the frequency and severity of storms might increase
changes in temp and amount of water might effect many species- changes in their distribution
carbon footprints
difficult to measure
= measure of the amount of carbon dioxide and other greenhouse gases released over a full life cycle of something
is difficult to measure
lots of different factors to consider
rough calculation can give idea of worst emitters
reducing carbon footprints
renewable energy sources or nuclear energy instead of fossil fuels
government could tax companies based on the amount of greenhouse gases they produce
cap on greenhouse gas emmisions
technology that captures CO2 by burning fossil fuels before it is released
making reductions is difficult
worried about effect on economic growth of communities- bad for peoples well being
most countries do not want to sacrifice their economic development if other countries wont do the same
individuals in developed countries need to change their lifestyles
air pollution
combustion of fossil fuels releases gases and particles
fossil fuels (crude oil) contain hydrocarbons which are oxidized so that carbon dioxide and water vapour are released
when theres not enough oxygen incomplete combustion occurs releasing carbon monoxide and particulates (soot)
particulates
if inhaled can get stuck in lungs and cause damage
cause global dimming- particulates do not let suns light through
carbon monoxide
prevents blood from carrying oxygen
does this by binding to hemoglobin which normally carries oxygen - so less oxygen is transported around body
a lack of oxygen can lead to fainting, coma, death
carbon monoxide is colorless and cannot be smelt- hard to detect
sulfur dioxides and nitrogen can be released
sulfur dioxide is released in the combustion of fossil fuels that contain sulfur impurities -sulfur becomes oxidized
nitrogen oxides are created by reaction between nitrogen and oxygen in the air caused by heat (car engines)
when these gases ix with clouds they form dilute nitric/sulfuric acid and fall as acid rain
acid rain kills plants and damages buildings and statues
they can cause respiratory problems in humans