2.3: Biogeochemical Flows Flashcards
How do humans impact biogeochemical cycles?
Activities such as:
Burning fossil fuels
Deforestation
Urbanization
Agriculture
Lead to imbalance, threaten sustainability
What is a store (in a biogeochemical cycle)?
Where elements are held for varying periods of time (reservoir)
Element remains in equilibrium with environment
- total input = total output
Can be natural or artificial
Examples:
- ocean is major store for carbon
-> stores dissolved CO2
-> equivalent amount of CO2 released back into atmosphere to maintain equilibrium
-> sea life also have complex carbon compounds
-> lots of CO2 stored in deep ocean ad inorganic compound
What is a sink (in a biogeochemical cycle)?
Represent parts the cycle where a particular element accumulates over time
- total input > total output -> net accumulation of the element
Can be natural or artificial
Example:
Fossil fuel deposits is sink for carbon
- store carbon that was once part of living organisms
What is a source (in a biogeochemical cycle)?
Sources release elements into the cycle
- total output > total input -> net release of element
Natural or artificial
Example:
Volcanic eruption release large amount of CO2
Why do biogeochemical cycles exist?
Some elements are finite
- need to be recycled to allow new organisms to be made and grow
Ex: carbon
Carbon constantly recycled so total amount of carbon is basically constant
What is an organic store? What are some organic stores for carbon?
Carbon-containing compounds found in organisms and fossil fuels
Organisms (carbohydrates)
crude oil, natural gas (hydrocarbons)
What is an inorganic store? What are some inorganic stores for carbon?
Réservoirs of carbon that exist in other non-living components of the biosphere
Atmosphere
Soil
Oceans
(CO2 or carbonates)
When is a carbon store at equilibrium?
A carbon store is inequilibriumwhen absorption (uptake) isbalancedby the release
Example:
Carbon stored in trees through photosynthesis = carbon released during respiration
What is residence time?
The average time that a carbon atom remains in a store
Without human interference:
Residence time of fossil fuels would be hundreds of millions of years
Why type of flow is photosynthesis?
Transformation
Creation of glucose from CO2, H2O
Release oxygen
carbon dioxide + water → glucose + oxygen + energy
6CO2 + 6H2O → C6H12O6 + 6O2
What type of flow is respiration?
Transformation
Break down glucose into CO2 and H2O
glucose + oxygen → carbon dioxide + water + energy
C6H12O6 + 6O2 → 6CO2 + 6H2O
What type of flow is feeding?
Transfer
Animal consume organic matter
Transfer carbon through food chain
What type of flow is combustion?
Transformation
Process of burning something
Fuel + oxygen → carbon dioxide + water
(CH4) + 2O2→ CO2+ 2H2O
What type of flow is death/decomposition?
Transfer/transformation
Breaking down of dead materials by bacteria/animals/fungi/decomposers
Needs warmth, moisture, lots of oxygen
What type of flow is defecation?
Transfer
Carbon returned to soil via waste
What type of flow is fossilization?
Animal/plant die in condition without decomposing microorganisms -> carbon can be converted over millions of years (+ high pressure) -> fossil fuels (ex peat, coal)
Aquatic organisms that die -> sediment on sea bed -> fossil fuel (ex oil, gas)
What is carbon sequestration?
The process of capturing atmospheric CO2 and storing it in solid or liquid forms
Ex:
trees naturally sequester carbon by absorbing CO2 + storing it in solid/liquid forms
Give an example of how an ecosystem can be a store, sink and source of carbon
Young forest ecosystem: sink
- photosynthesis > respiration
- net uptake of CO2
Mature forest ecosystem: store
- carbon cycling between living organisms, soil, atmosphere
Forest destruction: source
- releasing stored carbon back into atmosphere
Human impact on carbon cycle: fossil fuels
Fossil fuels -> stores of carbon with basically unlimited residence times
Formed when past ecosystems acted as sinks -> trapped organic carbon over millions of years
- from ancient plants/animals
- remains buried deep underground
- pressure + heat -> fossil fuels
Human burn fossil fuel for energy production
- burned -> release heat energy -> generate electricity
- powered vehicles, heat buildings, fuel industry
When burned -> carbon source
Human impact on carbon cycle: agricultural systems
Carbon sink or source -> depend on management
Sink:
Regenerative agriculture techniques
- crop rotation, cover cropping, no-till farming
- soil act as sink -> increase amount of organic matter in soil
Source:
- drainage of wetlands, monoculture farming, intensive tillage
- soil act as source -> increase release of carbon
Longer-term cropping practices (ex timber production) -> affect carbon cycling + storage
- sustainable management -> sequester CO2 + store -> sink
- unsustainable management -> carbon released when harvested wood burned > new tree growth -> source
Human impact on carbon cycle: oceanic carbon dynamics
CO2 absorbed into ocean by dissolving in sea water
- can also be released as gas if conditions change
Normally -> sink
- absorb CO2 from atmosphere to regulate atmospheric CO2 levels
-> however fossil fuels release CO2 > absorption of CO2 = rise in atmospheric CO2
Increases ocean temps
Increases climate change effects
Reduces ability of ocean to be sink
Human impact on carbon cycle: ocean acidification
Increased concentration of dissolved CO2 in ocean -> lower pH -> ocean acidification
Threat to marine organisms:
Calcium carbonate deposition in mollusk shells + coral skeletons
- weakened shells -> increased vulnerability
- less diverse reef structure
Methods of reducing human impact on carbon cycle (1)
Low carbon tech:
Tech that focuses on reducing energy consumption by improving efficiency of:
Transport, industry, buildings, other systems, etc
Ex: renewable energy, energy-efficient practices
- better insulation/heat pumps (20-30% less energy)
- LED lights (80% less energy)
- transportation (electric vehicle, hydrogen fuel cells, etc)
Reduction in fossil-fuel burning:
Transition to cleaner energy sources
Ex: redevable energy
Using biomass as fuel source:
Promote sustainable cultivation of bioenergy crops that DO NOT cause deforestation
Ex: bioenergy with carbon capture and storage (BECCS) technology
-> produce energy from biomass
-> CO2 emission from biomass combustion -> captured and sorted underground
Methods of reducing human impact on carbon cycle (2)
Réduction in soil disruption:
Through sustainable agricultural practices
- preserve soil health, maintain soil ability to sequester carbon (healthy soil = sink)
Ex:
- no-till farming, crop rotation, cover cropping to minimize soil disturbance/erosion/loss of organic matter
- protect + restore degraded soils
Reduction in deforestation:
Implement programs
- UN collaborative programme on reducing emission from deforestation and forest degradation in developing countries (UNREDD)
-> promote sustainable forestry practices (protect + allowances sequestration)
-> avoid converting forest land
Carbon capture through reforestation:
Planting trees on deforested/degraded land to sequester from atmosphere and industry
- tree absorb CO2 -> store carbon in biomass + soil
- forest important sink
- restore ecosystem
Methods of reducing human impact on carbon cycle (3)
Artificial sequestration:
Tech that captures CO2 emission from industrial processes + power plants -> prevent from entering atmosphere
- carbon capture and storage (CCS)
-> CO2 captured, transported injected underground for long-term storage
Enhancing CO2 absorption by the oceans:
Ocean fertilization techniques -> adding compounds like nitrogen, phosphorous, iron to stimulate growth of phytoplankton
- phytoplankton absorb CO2 via photosynthesis
Used to increase ocean upwellings
- nutrient rich deep water to surface
- same effect as artificially adding nutrients
Reducing practices that emit CO2:
Transportation
- cycling, walking, public transport
Circular economy
- reuse, recycle
Reducing energy consumption
- AC, heating less
