Chapter 7 - Biogeochemical cycles

• Phosphorus cycle

  The Phosphorus cycle doesn't include a gas phase, passing primarily through rocks, soil, water and living organisms.
• Components (P) - weathering of rocks

  Begins with the weathering of phosphate laden rocks, which releases phosphates into the soil and water.
• Components(P) - Uptake by plants/animals

  Plants absorb these phosphates from soil or water, and then animals obtain phosphorus by eating plants.
• Components(P) - Decomposition

  When plants and animals die and decompose, phosphorus returns to the soil or water. Which could be used again by plants.
• Components(P) - Sedimentation

  Over time, phosphorus in water can slowly sink and become part of rocks. The phosphorus can eventually be brought back to the surface through tectonic activity.
• Human influence(P) - mining/ fertilisers

  Mining of phosphorus for the production of artificial fertilisers has led to an increase in the amount of phosphorus entering ecosystems.
• Human influence(P)- eutrophication

  The excess phosphorus from fertilisers can cause eutrophication in water.
• Sustainable management(P)

  Shortage of phosphates is the limiting factor on crop productivity. It is reduced by the removal of biomass during harvesting and loss of phosphates with eroded soil.
• Carbon cycle - photosynthesis

  
  

  Captures light energy using chloropyll. It converts low-energy substances such as carbon dioxide and water into high energy carbohydrates.
• Carbon cycle - respiration

  Respiration releases the energy that was captured during photosynthesis which is then used to drive metabolic processes. Aerobic respiration returns the carbon to the atmosphere as carbon dioxide,
• Human influences(C) - changes in photosynthesis

  • Deforestation reduces the movement of carbon from the atmosphere in biomass
  • Afforestation increases the movement of carbon from the atmosphere into biomass.
  • Marine pollution with toxic materials can reduce phytoplankton population. This reduces absorption of dissolved carbon dioxide
• Human influences (C) changes in aerobic respiration

  The carbon in dead organic matter in the soil is gradually released as CO2 by the aerobic respiration of soil organism like bacteria and fungi.

  Ploughing increases the oxygen supply to decomposers living in the soil so aerobic decomposition takes place more rapidly.
• Sustainable management(C) - biomass carbon stores

  Habitats such as peat bogs and forests contain huge amounts of carbon.
• Sustainable management (C) - use of alternatives to fossil fuels

  Renewable energy resources and nuclear power produce lower CO2 emissions than fossil fuels
• Sustainable management(C) - carbon sequestration

  Large scale tree planting could remove a lot of CO2, from the atmosphere and slow down or reverse rising CO2 concentrations. Once a tree reaches full size there will no further net storage of carbon but the standing tree is a carbon reservoir.
• Carbon capture and storage

  Involves capturing carbon usually as CO2 so that is not release into the atmosphere.
• Pre combustion technology

  Gasification coverts a fuel such as coal into gaseous hydrogen and CO2. The CO2 can be removed for storage, and then the hydrogen can be distributed for use in vehicles. When burnt, the exhaust gases contain water vapour but no CO2.
• Nitrogen cycle- Fixation

  Some micro- organisms can chemically reduce nitrogen to ammonia. They may be free living bacteria in the soil.
• Nitrogen cycle - Nitrification

  Involves the oxidation of ammonia into nitrites then into nitrates by nitrifiying bacteria in the soil.
• Nitrogen cycle - leaching

  The high solubility of nitrates means they are easily leached out of soils into water where they act as nutrients for aquatic plants and algae.