Human influences on the environment Flashcards
1
Q
Why is carbon monoxide dangerous?
A
- When fossil fuels are burnt without enough air supply (oxygen) they produce the gas carbon monoxide (CO)
- Carbon monoxide is poisonous because if it combines with the haemoglobin in red blood cells. Carbon monoxide can kill people if the blood becomes so saturates with the gas that the blood can no longer carry enough oxygen for cellular respiration to take place - it prevents them from carrying oxygen
- Carbon monoxide is mostly released in car emissions
- Most modern cars are fitted with catalytic converters that turn the carbon monoxide into carbon dioxide, decreasing the amount of CO that is released into the atmosphere
2
Q
What is acid rain caused by?
A
- Burning fossil fuels releases harmful gases like CO2 (a GHG) and sulphur dioxide (SO2)
- The sulphur dioxide comes from sulphur impurities in the fossil fuels
- When this gas mixes with rain clouds it forms dilute sulphuric acid
- This then falls as acid rain
- Internal combustion engines in cars and power stations are the main cause of acid rain
- Acid rain is also caused by nitrogen oxides that are produced by burning fossil fuels
3
Q
Why is acid rain bad?
A
- Acid rain kills fish and trees
1. Acid rain can cause a lake to become more acidic. This has a severe effect on the lake’s ecosystem. Many organisms are sensitive to changes in pH and cannot survive in more acidic conditions. Many plants and animals die
2. Acid rain can kill trees. The acid damages leaves and releases toxic substances from the soil, making it hard for the trees to take up nutrients
4
Q
Describe the greenhouse effect
A
- Greenhouse gases trap heat from the Sun
1. The temperature of the Earth is a balance between the heat it gets from the Sun and the heat it radiates back out into space
2. Gases in the atmosphere absorb most of the heat that would normally be radiated out into space, and re-radiate it in all directions (including back towards Earth)
3. If this did not happen, then at night there would be nothing to keep any heat in, and we would get very cold
4. There are several different gases in the atmosphere that help keep the heat in and they are called “greenhouse gases” and they include, water vapour, carbon dioxide and methane
5. Human beings are increasing the amount of carbon dioxide in the atmosphere and we are also increasing levels of other gases that can act as greenhouse gases e.g. CFCs and nitrous oxide. This has enhanced the greenhouse effect
6. As a result of all this, the Earth is heating up, and this is global warming. Global warming is a type of climate change and causes other types of climate change e.g. changing rainfall patterns. Climate change could lead to thinks like changing crop growth patterns or flooding due to the polar ice caps melting
5
Q
How do humans increase the levels of carbon dioxide?
A
- Humans release carbon dioxide into the atmosphere all the time as part of our everyday lives, in car exhausts, industrial processes, as we burn fossil fuels etc
- People around the world are cutting down large areas of forest (deforestation) for timber and to clear land for farming and this activity affects the level of carbon dioxide in the atmosphere
6
Q
How do humans increase levels of methane?
A
- Methane gas is also produced naturally from various source e.g. rooting lands in marshland
- However, two ‘man-made’ sources of methane are on the increase: rice growing and cattle rearing, it is the cows “pumping” that is the problem
7
Q
How do humans increase levels of nitrous oxide?
A
- Nitrous oxide is released naturally by bacteria in soils and the ocean
- A lot more is released from soils after fertiliser is used
- It is also released from vehicle engines and industry
8
Q
How do humans increase levels of CFCs?
A
- CFCs are man made chemicals that were once used in aerosol sprays (e.g. deodorant) ad fridges, they are really powerful GHGs
- Most countries have agreed not to produce them any more because they also damage the ozone layer, which prevents UV radiation from reaching the Earth
- But some CFCs still remain and get released e.g. by leaks from old fridges
9
Q
What is the problem with fertiliser?
A
- Fertilisers can leach into water and cause eutrophication
- Nitrates and phosphates are put onto fields as mineral fertilisers
- If too much fertiliser is applied and it rains afterwards, nitrates are easily leached (washed through the soil) into rivers and lakes
- The result is eutrophication which can cause serious damage to rivers and lakes
10
Q
Describe eutrophication and its problems
A
- The nitrates leach from fertilisers in the soil into the water, fertilisers enter the water, adding extra nutrients (nitrates and phosphates)
- The extra nutrients and increased levels of nitrates cause algae to grow fast and block out the light
- Plants can not photosynthesise due to lack of light and start to die
- Algae die as they run out of nitrates
- Decomposers break down dead plants and algae using oxygen
- Oxygen levels in the water fall and animals cannot live in it, so organisms that need oxygen (e.g. fish) die
11
Q
What is another cause of eutrophication?
A
- Pollution of water by sewage
- Sewage contains lots of phosphates from detergents (e.g. washing powder), it also contains nitrates from urine and faeces
- These extra nutrients increase the number of micro-organisms that decompose the sewage causing depletion of oxygen and so animals cannot survive in it
12
Q
How does deforestation lead to leaching?
A
- Trees take up nutrients from the soil before they can be washed away (leached) by rain, but return them to the soil when leaves die
- When trees are removed, the soil is left exposed and nutrients/minerals get leached away, but do not get replaced, leaving infertile soil
13
Q
How does deforestation lead to soil erosion?
A
- Tree roots hold the soil together
2. When trees are removed, soil is left exposed, soil can be washed away by the rain (eroded) leaving infertile ground
14
Q
How does deforestation disturb the water cycle?
A
- Trees stop rainwater reaching rivers too quickly
- When they are cut down, rainwater can run straight into rivers, this can lead to flooding
- Transpiration from trees releases some of the rainwater back into the atmosphere
- When they are cut down this can make the local climate drier (lack of transpiration from the trees)
15
Q
How does deforestation disturb the balance of atmospheric oxygen and carbon dioxide?
A
- Forests take up CO2 by photosynthesis, store it in wood and slowly release it when they decompose (microorganisms feeding on bits of dead wood release CO2 as a waste product of respiration)
- When trees are cut down and burnt, the stored carbon is released at once as CO2. This also uses up oxygen and release more CO2 into the atmosphere. This contributes to global warming
- Fewer trees in the forest also means that less photosynthesis takes place, releasing less oxygen (and less CO2 therefore is taken in). This causes the oxygen level in the atmosphere to drop
- Trees take in carbon dioxide and produce oxygen when they photosynthesise
- After deforestation, carbon dioxide builds up in the atmosphere and less oxygen is made
- In addition, the trees are often burned, using up oxygen and putting even more carbon dioxide into the atmosphere
