Task 3: Biogeochemical cycles Flashcards
(49 cards)
What are Biogeochemical Cycles and how do they sustain life on Earth?
Matter on Earth is finite and must be recycled through biogeochemical cycles for use by living organisms. These process work by reycling essential elements like carbon, nitrogen, and oxygen through biological and geological processes.
- ‘Bio’ due to the role of living organisms
- ‘Geo’ due to geological processes
- ‘Chemical’ due to changes in element forms and compounds
What is a Reservoir (or Pool)? What are the four global reservoirs for elements?
Places where elements are stored. The four global reservoirs are the atmosphere, oceans, land and Earth’s crust (rocks).
Define Flux in the context of biogeochemical cycles.
The flow or transfer of elements between reservoirs.
What is the difference between a Source and a Sink?
A source releases more of an element than it accumulates; i.e. the influx is less than the outflux. This is where something (like a gas or nutrient) is released or given off more than it is taken in.
- Example: Imagine it like a faucet that pours out more water than it can store
A sink accumulates more than it releases, i.e. the influx is greater than the outflux. This is where something is taken in or absorbed more than it is released.
- Example: Think of it like a sponge that soaks up more water than it lets go
What does Residence Time refer to, and what is its significance for environmental impact?
The average time an element remains in a reservoir before moving to another one. It helps understand the long-term effects of disturbances, like CO2 staying in the atmosphere for centuries, influencing climate change.
Describe the process of Photosynthesis
Green plants use sunlight to convert carbon dioxide and water into oxygen and glucose.
How is the Earth an Open and Closed System?
Earth is an open system for energy (receives sunlight and loses heat)
Earth is a closed system for matter (finite and recycled)
What is the role of living organisms in biogeochemical cycles?
They recycle elements and contribute to maintaining the balance of these cycles through processes like photosynthesis.
How do human activities impact biogeochemical cycles
Human activities significantly disrupt natural biogeochemical cycles, leading to environmental degradation, climate change, and health risks. Activities include fossil fuel combustion, land-use change (deforestation, agriculture and mining).
What is the carbon cycle?
How carbon moves between the…
Rocks
- Organic(rock) & inorganic carbon(fossil fuels)
Atmosphere
- Carbon dioxide & Methane
Land Biosphere
- Soil, permafrost, plants, animals
Ocean
- Dissolved inorganic carbon, organic carbon
- Upper, mixed and deep layer
What is the primary form of carbon in the atmosphere, and what is its turnover time?
Carbon is primarily in the form of carbon dioxide (CO₂), with a turnover time of approximately 5 years.
Why do we need Carbon?
Capable of making very complex organic material
Needed for amino acids/proteins, lipids, carbohydrates, nuclear acids.
What are the turnover times of carbon in different reservoirs?
Rocks and sediments:
Millions of years
Atmosphere: 4 to 5 years (when in balance)
Ocean : Carbon in oceanic biosphere (surface) – 3 weeks; Mixed layer water – 5 years; Deep waters – 400 years
Land & land biosphere: 21 years
- Plant – few seconds
- Soil – 25 years
- Permafrost – long (as long as its frozen)
What are the major reservoirs (pools) of Carbon in the cycle?
Rocks and sediments: 99% of carbon stored in this reservoir; Includes organic(rocks) and inorganic carbon(fossil fuels).
Atmosphere: Tiny fraction of carbon on earth in this reservoir
Land: Largest pool for biological carbon, stored in soil, permafrost, plants and animals.
Ocean: Dissolved inorganic carbon(used to make organic carbon by marine life), dissolved organic carbon and particulate organic carbon(living and dead).
What are the human disturbances to the carbon cycle?
Fossil fuel burning for industry, housing, transport etc.
Land use change for agriculture, industry, mining, urbanization
Fossil fuel burning & digging up carbon in soil
Deforestation: Fire – releasing carbon, Limiting capacity of biosphere carbon sink
Livestock grazing causes release of carbon and methane
What are the consequences of human disturbance to the carbon cycle?
Increasing GHG effect: Climate change – temperature increase
Reducing capacity of carbon sinks
Ocean acidification:
- Excess of CO2 – reducing capacity for carbon sink
- PH level of ocean decreases, killing sea life, Bleaching of coral reefs
- Less ability to photosynthesis
What is the Phosphorus cycle?
The global phosphorus cycle involves the movement of phosphorus through: i) Rocks & sediments, ii) Land/terrestrial Biosphere and iii) Ocean/Marine Biosphere
Unlike nitrogen & carbon it lacks significant gaseous phase, relies on geological and biological processes. Thus, atmosphere reservoir can be neglected.
Why is Phosphorus important?
Phosphorus is essential for life and is an essential nutrient often in short supply, like nitrogen.
Critical for plant growth and energy transfer in living organisms.
Phosphorus is a key component in several fundamental biological molecules.
- Phospholipids: Essential for cell membrane formation
- DNA/RNA: Integral part of the genetic material structure
- ATP (Adenosine Triphosphate): Critical for energy transfer within cells, containing high-energy phosphorus bonds
Draw the Phosphorus Carbon cycle and its reservoirs and fluxes.
What are the major reservoirs (pools) of phosphorus in the cycle?
Rocks and Sediments:
- These act as the largest long-term reservoir for phosphorus, storing it over geological timescales.
Ocean/Marine Biosphere:
- Phosphorus is dissolved in seawater and is also found in plankton, marine plants, fish, and other marine organisms.
- It plays a vital role in marine ecosystems and is often buried in sediments over time.
Land/Terrestrial Biosphere: - This includes soils, plants, and animals. Phosphorus is essential for plant growth and is cycled through living organisms and the decomposition of dead matter.
What are the major anthropogenic reservoirs (pools) of the global phosphorus cycle?
Agriculture soils
- Extensive use of phosphate fertilizers, agricultural soils have become a major anthropogenic pool where phosphorus is accumulated.
- However, much of this phosphorus is not readily available for plants and can lead to runoff.
Fertilizers
Phosphorus-Rich Deposits in rocks
- Released through mining
Human and animal waste
What are the key fluxes (movements) of phosphorus in the natural cycle?
Weathering: Natural processes like rain, erosion, and weathering cause rocks to release phosphates into soils and water
Absorption/ Uptake: Absorption of phosphorus from soil and water by plants and animals
Decomposition: When plant, animals and microbes die their organic phosphorus is broken down and made available to other organism
Leaching: refers to the movement of phosphorus (usually in the form of dissolved phosphates) from the soil into groundwater or surface water systems
Wind erosion: Movement of phosphorus particles through the air
Runoff in rivers and streams: Carries phosphorus from land to ocean
Geological uplift: Sedimentation of the phosphorus formation of new rock
What are the major anthropogenic fluxes of the global phosphorus cycle?
Increased Phosphorus Losses Due to Land-Use Changes:
- Erosion from Croplands: Water and wind erosion result in a loss from croplands, like the amount added through fertilizers
- Erosion from Grazing Lands: Overgrazing causes a loss of phosphorus
Phosphorus from Human and Animal Waste:
- Point and Nonpoint Sources: Waste from humans and animals contributes to increased phosphorus runoff into water bodies
Impact on Phosphorus Transport:
- Increased Transfer to Oceans: Human activities have increased phosphorus transfer from land to oceans by 50-300%
