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Section N: Cycles and Human Influences (carbon cycle (these elements…
Section N: Cycles and Human Influences
carbon cycle
these elements include: carbon, nitrogen, phosphorus and sulphur
the cycles are dependant on a variety of bacteria
the atoms of the twenty or so elements that make up living organisms are constantly cycled between the living environments
only process that removes carbon dioxide from the atmosphere is photosynthesis
only a fixed amount of carbon in the world so it is constantly recycled
the whole process is powered by photosynthesis. Green plants use the carbon from CO2 in the air to make carbohydrates, fat and proteins
eating passes the carbon compounds in the plant along to animals in a food chain or web
both plant and animal respiration while the organisms are alive releases CO2 back into the air
plants and animals eventually die and decompose, or are killed and turned into useful products
when plants and animals decompose they're broken down by bacteria and fungi. These decomposers release CO2 back into the air by respiration, as they break down the material
some useful plant and animal products e.g. wood and fossil fuels, are burned (combustion). This also releases CO2 back into the air
Eutrophication
fertilisers can leach into water & cause eutrophication
fertiliser ends up in lakes & rivers
1) nitrates & phosphates are put onto fields as mineral fertilisers
2) if too much fertiliser is applied and it rains afterwards, nitrates are easily leached into rivers & lakes
3) result is eutrophication, causing serious damage to rivers & lakes
greenhouse gases
water vapour
carbon dioxide
methane
nitrous oxide
CFCs
how human influences contribute to greenhouse gases
CO2
car exhausts, industrial processes, burning fossil fuels
deforestation to make timber and clear area for farming - affects level of CO2 in the atmosphere
methane
produced naturally from sources such as rotting plants in marshland
rice growing and cattle rearing cows' "pumping" is a problem
nitrous oxide
released naturally by bacteria in soils and the ocean
released from vehicle engines and industry
lots more released from soil after fertilisers are used
CFCs
man-made chemicals that were once used in aerosol sprays and fridges. Really powerful greenhouse gases
most countries have agreed not to produce them anymore because they also damage the ozone layer, which prevents UV radiation from reaching Earth
some CFCs are still released e.g by leaks from old fridges
Deforestation
soil erosion
without tree roots intercepting the water & establishing the soil, the soil is washed away into rivers
the remaining sub-soil is not fertile
effects on water cycle
fewer trees = less transpiration
affects rainfall over wider area than just deforested part
water cycle is disturbed - draught (desertification)/flooding
leaching
without tree roots taking up minerals
they are washed into water courses
land left with no minerals so fertilisers must be used for crops e.g. in Indonesia
balance of gases
increase carbon dioxide/enhanced greenhouse effect due to reduced uptake by plants
the permanent removal of vast areas of forest
reasons for deforestation
driven by world population increase - use land (farming, buildings/roads, biofuels)
greenhouse effect and global warming
if this didn't happen, at night there'd be nothing to keep any heat in, and it'd be very cold
greenhouse gases keep heat in
gases in the atmosphere absorb most of the heat that would normally be radiated out into space, and re-radiate it in all direction (including back into Earth)
humans are increasing amount of CO2 in the atmosphere as well as other gases e.g. CFCs and nitrous oxide which enhances the greenhouse effect
temperature of Earth is a balance between the heat it gets from the sun and the radiates back out into the atmosphere
this causes global warming. Global warming is a type of climate change (CC) & causes other climate change e.g. changing rainfall patterns. CC could lead to changing crop growth or flooding due to the polar ice caps melting
air pollution
carbon monoxide
poisonous
1) when fossil fuels burnt without enough air supply they produce CO
2) combines with red bloods cells, prevents them from carrying oxygen
3) mostly released in car emissions. Most modern cars are fitted with catalytic converters that turn CO into CO2, decreasing the amount of CO released into the atmosphere
acid rain
when this gas mixes with rain clouds it forms dilute sulfuric acid
the sulfur dioxide comes from sulfir impurities in the fossil fuels
this then falls as acid rain
burning fossil fuels releases harmful gases like CO2 and sulfur dioxide (SO2)
internal combustion engines in cars & power stations are the main causes of acid rain
causes lakes to be more acidic - plants and animals die due to change in pH conditions
kills trees - damages leaves and releases toxic substances from the soil, making it hard for trees to take up nutrients
