The Physical Environment (AS); Biogeochemical Cycles Flashcards
Why are biogeochemical processes significant and what do they show?
Nutrients are processed, converted and recycled. Interlinked cyclical processes mean that small # of material continually recycled can support ecosystems over long time. Biogeochemical cycles show processes moving particular elements between their reservoirs in biosphere, atmosphere, hydrosphere and lithosphere
What are the main reservoirs in the carbon cycle and why is there little changes to the amount of carbon?
In state of dynamic equilibrium so little/no change in # of carbon in each reservoir of cycle
Atmosphere- CO², methane, CO
Hydrosphere- hydrogen carbonate ions, dissolved CO²; surface waters 500 Gt + deep ocean 35,000 Gt
Biosphere- Carbs (cellulose,starch, etc), proteins,lipids; living organisms 470 Gt + 3700 Gt
Lithosphere- Carbonaceous rocks like limestone 20m Gt, fossil fuels 10,000 Gt
How are photosynthesis and respiration a process in the carbon cycle?
Photosynthesis- captures light energy using pigments like chlorophyll. Makes CO² & H²O into carbs, could be converted into proteins & lipids
Respiration- Releases energy captured in photosynthesis to drive metabolic processes. Aerobic returns carbon to atmosphere as CO² & breaks down organic compounds more completely and w/ more energy than anaerobic- which allows some organisms to survive + use food sources in O²-deficient environments. usually returns CO² to atmosphere as methane.
How are food webs, fossilisation and combustion processes in the carbon cycle?
Food webs- Some carbs, proteins,lipids made by plants are eaten by herbivores; may then be eaten by carnivores. Feeding relationships combine to make food webs
Fossilisation- Incomplete decomposition of dead organic matter, often in anaerobic conditions; can make substances forming long-term carbon stores (e.g fossil fuels) Organisms like molluscs make exoskeletons including calcium carbonate. Can make rocks like limestone- now contain most of carbon in lithosphere
Combustion- Burning of organic materials releases CO². Natural fires in forests may start by lightning
How do humans affect the carbon cycle + examples?
Many human activities alter rates of movement of Carbon through cycle. Can unbalance natural dynamic equilibrium of cycle + change distribution of Carbon in reservoirs of cycle. Things humans affect:
- changes in photosynthesis
- changes in aerobic respiration
- changes in anaerobic respiration
- carbonic acid concentration in sea
- methane releases from fossil fuels
- combustion
- biomass movements
How do anthropogenic changes in photosynthesis affect the carbon cycle?
- Deforestation ↓ movement of Carbon from atmosphere → biomass
- afforestation ↑ movement of carbon from atmosphere → biomass
- marine pollution w/ toxic materials ↓ phytoplankton populations =↓ absorption of dissolved CO² . Some naturally sink to seabed after dying,↑# of carbon in marine sediments.
How do anthropogenic changes in aerobic respiration affect the carbon cycle?
Carbon in dead organic matter in soil → gradually released as CO² by aerobic respiration of soil organisms, esp bacteria + fungi
Ploughing ↑O² supply to decomposers living in soil so aerobic decomposition = more rapid. # of carbon in soil dead organic matter store ↓ & amount in atmosphere ↑.
How do anthropogenic changes in anaerobic respiration affect the carbon cycle?
Absence of O² → respiration by anaerobic soil organisms releases methane. If released into atmosphere → gradually oxidised to CO²
Anaerobic environments made by human activities:
- rice paid fields
-landfill sites
- anaerobic sediments in reservoirs
- livestock intestines
Anaerobic environments destroyed by drainage:
- waterlogged fields
- marshlands
- peat bogs
How do anthropogenic changes in the carbonic acid concentration in the sea affect the carbon cycle?
Humans don’t directly cause CO² to dissolve/ exsolve but their activities affecting concentration of CO² in atmosphere will after these processes, making a new equilibrium.
Dissolved CO² is in equilibrium w/ carbonic acid which dissociates, making hydrogen carbonate + hydrogen ions. Conc of hydrogen ions affects pH of sea = ↑ in dissolved CO² = ↓ pH of water. As atmospheric CO² conc ↑ dissolved CO² conc. ↑, so hydrogen ion conc. ↑→ sea more acidic.
How do anthropogenic changes in combustion and methane releases affect the carbon cycle?
Combustion of fossil fuels & wood releases large # of CO² into atmosphere.
Methane may be released into atmosphere during fossil fuel extraction.
How do anthropogenic changes in biomass movements affect the Carbon cycle?
Humans don’t directly move large # of carbon in biomass betw. areas, but they can produce local changes w/ environmental impacts:
- addition of compost/ mulch to improve soil fertility;
- deforestation & crop harvesting → reduced soil organic matter & soil erosion;
- movement of biomass into sea when sewage is discharged;
- movement of marine biomass → terrestrial system by fishing/aquaculture
How can human impacts on the carbon cycle be counteracted?
A range of strategies of sustainable management:
- conservation of biomass carbon stores
- use of alternatives to fossil fuels
- Carbon sequestration
- carbon capture and storage (ccs)
How does conservation of biomass carbon stores and the use of alternatives to fossil fuels counteract human impacts on the Carbon cycle?
Habitats like peat bogs & forests have huge # of Carbon - protecting these from exploitation/damaging land-use change = important to prevent even↑CO² releases
Renewable energy resources & nuclear power make ↓CO² emissions than fossil fuels.
How does carbon sequestration counteract human impacts on the carbon cycle?
Large-scale tree planting could remove a lot of CO² from atmosphere & slow/reverse ↑CO² conc. Once tree reaches full size there’ll be no further net storage of Carbon but standing tree = carbon reservoir. If trees were harvested & kept as wood → replanting would make + Carbon storage as new tree grows.
What is Carbon capture and storage (ccs)?
Involves capturing carbon, usually as CO² , so that its not released into atmosphere
