Task 3: Biogeochemical cycles Flashcards
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%
What are the typical turnover times of phosphorus in different reservoirs?
Soils: 10 to 100 years, influenced by soil type and climate
Freshwater Systems: Weeks to a few years in lakes and rivers
Oceans: 10-20 years in surface waters; millions of years in deep ocean sediments
Geological Reservoirs: Tens to hundreds of millions of years
What are the primary sources of phosphorus?
Weathering of Rocks: Releases phosphorus into soils and water bodies
Human Activities: Mining and fertilizer use increase the availability of phosphorus
What are the primary sinks of phosphorus?
Marine Sediments: Long-term storage of phosphorus in sediments, making it largely in accessible
Terrestrial Soils: Phosphorus binds to soil particles, forming insoluble compounds
Biological Uptake: Temporarily stored in plants and microorganisms, released upon their decomposition
How have human activities altered the phosphorus cycle?
Fertilizer Use: Increased phosphorus availability in soils and runoff into water bodies
Soil Erosion: Agricultural practices lead to the loss or excess of phosphorus from soils, reducing fertility
Waste Management: Human and animal waste adds phosphorus to ecosystems, affecting water quality
What are the consequences of human-induced changes to the phosphorus cycle?
Eutrophication: Excess phosphorus causes algal blooms, oxygen depletion, and loss of aquatic biodiversity
Soil Degradation: Overuse of phosphorus fertilizers leads to reduced soil fertility and sustainability
Disruption of Natural Cycles: Increased phosphorus flux from land to oceans disrupts ecosystem balance and contributes to long-term changes in soil and water chemistry
What management strategies can be used to mitigate the impacts of altered phosphorus cycling?
Sustainable Fertilizer Use: Reducing overapplication and using organic alternatives
Erosion Control: Implementing soil conservation practices to reduce phosphorus runoff
Policy and Regulation: Enforcing guidelines for phosphorus use and managing agricultural runoff.
What are the main reservoirs of nitrogen in the natural nitrogen cycle?
Atmosphere: Contains almost all nitrogen relevant to biogeochemistry, making up 78% of the atmosphere (N₂)
Organic & Inorganic Nitrogen Pools:Found in soils and terrestrial vegetation in relatively small amounts
Oceans, Rocks, and Sediments: Contain small quantities of nitrogen
What are the main fluxes in the natural nitrogen cycle?
Nitrogen Fixation: Conversion of atmospheric nitrogen (N₂) into biologically available forms (ammonia NH₃) by bacteria or lightning
Denitrification: Conversion of biologically available nitrogen back to N₂ gas, returning it to the atmosphere.
Nitrogen Cycling within Terrestrial Ecosystems (run-off of water soluble forms): Nitrogen cycles tightly, with movement within the system being four times greater than inputs and losses.
Sedimentation: Removing nitrogen from the atmosphere into sedimentation
Why is nitrogen important for living organisms?
Amino Acids/Proteins: Building blocks of proteins, containing amine (–NH₂) and carboxyl (–COOH) functional groups
Genetic Material: Nitrogen is essential for DNA structure, especially in guanine and other nitrogenous bases
What is the role of bacteria in the nitrogen cycle?
Bacteria help make nitrogen available for plants and other organisms through:
Nitrogen Fixation: Conversion of atmospheric N₂ into ammonia (NH₃) by nitrogen-fixing bacteria
Nitrification: Conversion of ammonia into nitrite (NO₂⁻) and then nitrate (NO₃⁻)
Assimilation: Uptake of nitrate by plants, which convert it into organic nitrogen.
Denitrification: Conversion of nitrate back into nitrogen gas (N₂) by bacteria.
What are the steps involved in returning nitrogen to the atmosphere?
Ammonification: Decomposition releases nitrogen back as ammonia
Nitrification: Ammonia is converted into nitrite (NO₂⁻) and then nitrate (NO₃⁻)
Denitrification: Bacteria convert nitrate (NO₃⁻) back into nitrogen gas (N₂), releasing it into the atmosphere
What are the types of nitrogen fixation?
Biological Nitrogen Fixation: Carried out by bacteria (e.g., free-living bacteria in soil or aquatic systems or symbiotic bacteria in association with plants)
Non-biological Nitrogen Fixation: Occurs through lightning and industrial processes
What is the role of symbiotic nitrogen-fixing bacteria?
Symbiotic bacteria live in close association with host plants (primarily legumes)
In root nodules, they convert atmospheric nitrogen (N₂) into biologically available forms by breaking the strong triple bond of nitrogen molecules
What is the impact of human activities on the nitrogen cycle?
Human activities such as:
Industrial processes
Agriculture, and
Fossil fuel combustion disrupt the nitrogen cycle, leading to increased nitrogen deposition and pollution
How have humans significantly altered the nitrogen cycle?
Humans have altered the nitrogen cycle primarily through:
Industrial fixation of nitrogen for fertilizers
Cultivation of nitrogen-fixing crops
Combustion of fossil fuels
How has the Haber process affected the nitrogen cycle?
The Haber process converts atmospheric nitrogen (N₂) into ammonia (NH₃) for fertilizer production, more than doubling the amount of nitrogen fixed from the atmosphere into terrestrial systems
By the 2000s, it accounted for 100 Tg (teragrams) of nitrogen fixed annually, with further increases projected
What are the consequences of human alterations to the nitrogen cycle?
Increased Greenhouse Gases:
Nearly doubled atmospheric nitrous oxide (N₂O), contributing about 6% to total greenhouse warming
Eutrophication:
Nitrogen runoff causes nutrient overloading in aquatic systems, depleting oxygen and creating dead zones
Air and Water Pollution:
Nitrogen emissions contribute to smog, acid rain, and nitrate contamination of groundwater
Biodiversity Loss:
Nitrogen deposition favors nitrogen-demanding species, reducing biodiversity in ecosystems
What is eutrophication, and how is it linked to the nitrogen cycle?
Eutrophication is caused by excessive nitrogen runoff into aquatic systems, leading to nutrient overloading.
This results in algal blooms, which deplete oxygen in the water and create “dead zones” that harm aquatic life
How does increased nitrogen affect greenhouse gas emissions?
Human activities have nearly doubled the atmospheric concentration of nitrous oxide (N₂O), a potent greenhouse gas, contributing about 6% to total greenhouse warming
N₂O is approximately 300 times more potent than CO₂ in terms of warming potential
How does nitrogen contribute to air and water pollution?
Air pollution:
Nitrogen emissions contribute to smog formation and acid rain, harming human health and ecosystems
Water pollution:
Nitrate contamination of groundwater, often due to agricultural runoff, poses a risk to drinking water quality and can lead to health issues like methemoglobinemia (“blue baby syndrome”)
How does nitrogen deposition lead to biodiversity loss?
Nitrogen deposition alters plant species composition by favoring fast-growing, nitrogen-demanding species, which outcompete other plants
This reduces biodiversity, particularly in nutrient-poor ecosystems like grasslands and heathlands
What are the key human activities that disrupt the nitrogen cycle?
Industrial Nitrogen Fixation:
- The Haber-Bosch process has significantly increased nitrogen in terrestrial and aquatic ecosystems
Cultivation of Nitrogen-Fixing Crops:
- Leguminous crops host nitrogen-fixing bacteria in root nodules, adding nitrogen to soils
Fossil Fuel Combustion:
- Releases nitrogen oxides (NOₓ) into the atmosphere, contributing to air pollution and acid rain
What does the scientific sustainability definition of Karl-Henrick Robert emphasize?
The Definition emphasizes the need for human activities to align with natural cycles, maintain balance, and respect ecological limits
It is based on scientific principles such as conservation of matter and energy, the role of photosynthesis, and geological cycles
What is strong sustainability? What is weak sustainability?
Strong sustainability emphasizes
- the non-substitutability of natural capital,
- the need to maintain ecological integrity,
- and the respect for ecological thresholds and limits
Weak sustainability suggests:
- that human-made capital can substitute natural capital, as long as the overall capital stock remains intact
- It tends to prioritize economic growth alongside environmental considerations
What are the key points of the Scientific sustainability definition? Is it a weak of strong approach of sustainability?
Emphasizes human activities aligning with natural cycles, maintaining balance, and respecting ecological limits
It is grounded in scientific principles like conservation of matter, energy, photosynthesis, and geological cycles
Reflects strong sustainability by emphasizing ecological integrity, the non-substitutability of natural capital, and the need for long-term resilience within natural boundaries.
