Biogechemical Cycles Flashcards
(10 cards)
Main processes of nitrogen cycle
Ionisation-processes such as lightning proved energy for atmospheric N and O to react and form NOx
Fixation-microorganisms can chemically reduce N to ammonia
Nitrification-oxidation of ammonium ions to nitrites then nitrates by nitrifying bacteria
Denitrification-reduction of nitrates in soil to N and N gases by gentrifying bacteria in the soil
Ammonification- proteins released as ammonium ion by derived as they decompose dead organic matter
Leaching -high solubility of nitrates means they are easily leached out of solid into water bodies where they are absorbed by plants
Harber process
Producing ammonia from N and H
Ammonia may then be converted into nitrates for fertilisers (using iron catalyst at high temp)
Main processes in phosphorus cycle
Absorbtion by roots -plants absorbs phosphates
Decomposition-breakdown of phosphates in DOM
Sedimentation-phosphates may become incorporated in sediments and not available to organisms to productivity of surface waters decreases
Weathering-mobilise the phosphate ions within the sediments
Processes of carbon cycle
Photosynthesis: takes carbon from atmosphere
Respiration: produces carbon for atmosphere
Food webs - products of photosynthesis (proteins etc) eaten by animals
Fossilisation-incomplete decomposition of DOM can produce fossil fuels(under anaerobic conditions).
Combustion-burning of fossil fuels produces CO2
How humans affect the carbon cycle
Changes on photosynthesis:
-deforestation
-afforestation
-marine pollution causes reduction of absorbed dissolved carbon dioxed(phytoplankton population reduced)
Changes in aerobic respiration:
-ploughing increases the oxygen supply to decomposers so aerobic decomposition take up more rapidly
Changes in anaerobic respiration:in the absence on O anaerobic respiration release methane which gradually oxidises to CO2
Anaerobic environments produced by human activities -
-rice PADI fields
- landfill sites
Combustion
Methane released from fossil fuels
How to sustainable manage the carbon cycle
Conservation of biomass carbon storage-habitats such at peat bogs contain huge amounts of C, prevent them from being exploited prevents CO2 being released
Use of alternate fossil fuels - renewable energy resources and nuclear energy produce less CO2 than fossil fuels
Carbon sequestration- large scale tree planting could reduce a lot of CO2 in atmosphere
Carbon capture and storage (CCS)
Trapping CO2 and not realising in into the atmosphere by using new tech such as:
Pre combustion tech- changing the fuel used or the way it’s combusted.
-gasification coverts coal into H(g) and CO2 which is then removed, the H can be used to power homes/vehicles
Post combustion tech: CO2 removed from exhaust gases of fossil fuels.
-dissolving on solvent
-graphene adsorption
Storage - after CO2 is captured could be stored underground
Human impacts on the nitrogen cycle
Haber process-ammonia is produced from N and H using iron catalyst and high temp
Agriculture - use of nitrate fertilisers may increase problems caused by leaching- eutrophication, draining of fields makes the soil more aerobic increasing the number of aerobic nitrifying bacteria and reduces the number of anaerobic denitrifying bacteria.
Pollution - NOx are released into the atmosphere by combustion processes and increases the quantity of nitrates washed into the soil by rain
Sustainable management of N-cycle
Control of combustion processes- less combustion=less NOx
Control of NOx release-catalytic converters and urea sprays
Eutrophication- ammonium compounds are converted into intrigues and nitrates which can cause eutrophication
Organic fertilisers - manure, sewage can be used as organic fertilisers to increase nutrient and humus levels
Management of soil process to increase soil nitrate levels-
-crop rotation
- cultivation of legume crops
Human impacts on phosphorus cycle
Mining of phosphate rocks-
Calcium phosphate is mined then treated to produce ammonium phosphate(more soluble)
Fertiliser use- fertilisers mobilise phosphorus compounds into the environment
Sustainable management of P-cycle
Biological wastes should be used as fertilisers to maintain phosphate nutrient availability
Crop breeding programs are increasing the efficiency of phosphate absorption
