C13/14 Flashcards
What is the composition of the atmosphere and how long has it been like this
About four-fifths (approximately 80%) nitrogen
About one-fifth (approximately 20%) oxygen
Small proportions of various other gases, including carbon dioxide, water vapour and noble gases
Been like this for 200 million years
Why is evidence of the early atomsphere limited
The time scale is 4.6 billion years and this is too big
What is the theory for Earth’s atmosphere today?
First billion years of the Earth’s existence there was intense volcanic activity that released gases that formed the early atmosphere
Water vapour condensed to form the oceans.
At the start of this period the Earth’s atmosphere may have been like the atmospheres 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 dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere.
How did oxygen levels increase
Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis
What did the increase in oxygen mean for the Earth
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 increased to a level that enabled animals to evolve
How did carbon dioxide decrease
Algae and plants decreased CO2 by photosynthesis
CO2 was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon
What do humans use earths resources for
To provide warmth, shelter, food and transport
What do natural resources provide
Supplemented by agriculture, natural resources provide food, timber, clothing and fuels
What are finite resources used for
Finite resources from the earth, oceans and atmosphere are processed to provide energy and materials
What is potable water
Water that is safe to drink
This is not pure water in a chemical sense as it contains dissolved substances
What is fresh water
Water that collects in the ground and in lakes and rivers
How is most potable water produced
Choosing appropriate source of fresh water
Passing water through filter beds
Sterilisation
What are some sterilisation agents used for cleaning water
Ultraviolet light
Chlorine
Ozone
When is desalination used
When supplies of fresh water are limited
How is desalination done
Distillation
Processes that use reverse osmosis
These require lots of energy
What does sewage treatment include
Screening and grit removal
Sedimentation to produce sewage sludge and effluent
Anaerobic digestion of sewage sludge
Aerobic biological treatment of effluent (to breakdown organic matter including microbes)
What is waste water
Urban lifestyles and industrial processes produce large amounts of waste water that require treatment before being released into the environment
What are some new ways of extracting copper from low grade ore
Phytomining and bioleaching
These avoid mining methods and digging, moving and disposing of large amounts of rocks
What is phytomining
Plants absorb metal compounds. The plants are harvested and then burned to produce ash that contains metal compounds
What is bioleaching
Uses bacteria to produce leachate solutions that contain metal compounds
How are metal compounds processed to produce metal
Copper can be obtained from solutions of copper compounds by displacement using scrap iron or by electrolysis
What does LCA stand for and what is it’s purpose
Life cycle assessments (LCAs) are carried out to assess the environmental impact of products
What do we measure to determine the LCA
• extracting and processing raw materials
• manufacturing and packaging
• use and operation during its lifetime
• disposal at the end of its useful life, including transport and
distribution at each stage.
Why can an LCA be a subjective process ( opinion )
Use of water, resources, energy sources and production of some wastes can be fairly easily quantified.
However, allocating numerical values to pollutant effects is less straightforward and requires value judgements, so LCA is not a purely objective process
Why can an LCA be adapted or unfair
Selective or abbreviated LCAs can be devised to evaluate a product but these can be misused to reach pre-determined conclusions, eg in support of claims for advertising purposes
What does reduce, reuse and recycling do
The reduction in use, reuse and recycling of materials by end users reduces the use of limited resources, use of energy sources, waste and environmental impacts
How do materials use up resources
Metals, glass, building materials, clay ceramics and most plastics are produced from limited raw materials.
Much of the energy for the processes comes from limited resources.
Obtaining raw materials from the Earth by quarrying and mining causes environmental impacts
What happens to glass bottles after use
Glass bottles can be crushed and melted to make different glass products.
Other products cannot be reused and so are recycled for a different use
How are metals recycled
Metals can be recycled by melting and recasting or reforming into different products.
The amount of separation required for recycling depends on the material and the properties required of the final product.
For example, some scrap steel can be added to iron from a blast furnace to reduce the amount of iron that needs to be extracted from iron ore
formation of deposits of limestone, coal, crude oil and natural gas.
. Idea of becoming compressed and trapping rock
What is a source of atmosphric pollution?
The combustion of fuels is a major source of atmospheric pollutants.
What are realsed to the atmosphere when fuels are burnt
The gases released into the atmosphere when a fuel is burned may include carbon dioxide, water vapour, carbon monoxide, sulfur dioxide and oxides of nitrogen. Solid particles and unburned hydrocarbons may also be released that form particulates in the atmosphere.
describe how carbon monoxide, soot (carbon particles), sulfur dioxide and oxides of nitrogen are produced by burning fuels
Incomplete combustion of hydrocarbons in coal and crude oil releases carbon particulates (soot) and carbon monoxide
Combustion of fossil fuels with sulfur impurities
Reaction between nitrogen and oxygen with the heat of buring
Both mean (nitrogen and sulphur become oxdised)
What is the problem with increased 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.
state examples of natural products that are supplemented or replaced by agricultural and synthetic products
Rubber (from tree sap) - now polymers (use in tires)
High crop yields due to development of fertilsiers.
What need to be removed from each bit of waste water
.
Sewage and agricultural waste water require removal of organic matter and harmful microbes.
Industrial waste water may require removal of organic matter and harmful chemicals.
Pros and cons of sewage treatment compared with desalination
Desalination requires more energy
Sewage teatemnets require more processs (and people don’t want tp drink water that was sewage)
