ESS Subtopic 2.3: Biogeochemical Cycles

subtopic 2.3: Biogeochemical cycles

https://eduinput.com/introduction-to-biogeochemical-cycles/

Biogeochemical cycles play a crucial role in maintaining the availability of essential chemical elements for living organisms. These cycles involve the movement and transformation of elements like carbon, nitrogen, and phosphorus between different environmental compartments such as the atmosphere, hydrosphere, lithosphere, and biosphere.

Human activities, such as burning fossil fuels, deforestation, and agriculture, significantly impact these natural cycles, often leading to imbalances that can affect the sustainability of ecosystems. Understanding and managing human impacts on biogeochemical cycles is vital for ensuring the health and stability of our environment

This unit is a minimum of 4 hours.

Guiding Questions

How do human activities affect nutrient cycling, and what impact does this have on the sustainability
of environmental systems?
What are the key processes involved in the carbon, nitrogen, and phosphorus cycles, and how do they interact within ecosystems?
How do changes in biogeochemical cycles influence ecosystem services and biodiversity?

Understandings

introduction to bioGeochemical cyles

2.3.1 Biogeochemical cycles ensure chemical elements continue to be available to living organisms.

Define the term "biogeochemical cycle"

BIOGEOCHEMICAL CYCLE COMPONENTS by Anton Antonio April 3, 2015

Biogeochemical cycles are closed systems that insure the natural processes that recycle nutrients in various chemical forms from the environment to organisms and then back to the environment. These cycles are crucial for sustaining life on Earth as they ensure that essential chemical elements remain available to living organisms. The primary biogeochemical cycles include the carbon, nitrogen, and phosphorus cycles. These cycles involve complex interactions between the atmosphere, hydrosphere, lithosphere, and biosphere.

Human activities have significantly altered biogeochemical cycles, leading to various environmental challenges. For instance, the burning of fossil fuels, deforestation, and industrial activities have increased the levels of carbon dioxide in the atmosphere, contributing to climate change. Agricultural practices and the use of fertilizers have increased the levels of nitrogen and phosphorus in soil and water bodies, often leading to nutrient pollution and eutrophication.

2.3.2 Biogeochemical cycles have stores, sinks and sources.

Define the terms "stores," "sinks," and "sources" in the context of biogeochemical cycles
Discuss the roles of stores, sinks, and sources in maintaining the balance of biogeochemical cycles.

Biogeochemical cycles are fundamental processes that recycle elements through Earth's systems, ensuring that essential nutrients remain available to living organisms. These cycles, including the carbon, nitrogen, and phosphorus cycles, involve interactions between the atmosphere, hydrosphere, lithosphere, and biosphere. These cycles consist of various components, such as stores, sinks, and sources, and involve matter moving through biotic (living) and abiotic (non-living) parts of ecosystems via transfers and transformations.

Stores, Sinks, and Sources

Stores (Storages):
- Stores are components of biogeochemical cycles where elements are held or stored for varying lengths of time. These can be in the form of reservoirs like the ocean, soil, atmosphere, or living organisms.
- Examples include carbon stored in fossil fuels, nitrogen in the soil, and phosphorus in sediments.
- When in equilibrium, these stores maintain a balance with their surroundings, meaning the rate at which elements enter and leave the store is roughly equal.
Sinks:
- Sinks are parts of the cycle where there is a net accumulation of elements. This means that more of the element is being absorbed or stored than is being released.
- Examples include forests acting as carbon sinks by absorbing more CO₂ during photosynthesis than they release through respiration, and oceans absorbing excess atmospheric CO₂.
- Sinks play a crucial role in regulating the concentration of elements in the environment, helping to mitigate potential imbalances.
Sources:
- Sources are parts of the cycle where there is a net release of elements into the environment. This means that more of the element is being released from the store than is being absorbed or stored.
- Examples include fossil fuel combustion, which releases stored carbon into the atmosphere as CO₂, and agricultural activities that release nitrogen from the soil into the air as nitrous oxide (N₂O).
- Sources contribute to the availability of elements in different forms and locations, which can have both positive and negative impacts on ecosystems.

Matter Flows in Ecosystems

Transfers: Transfers involve the movement of matter without changing its form. For example, the movement of water through the water cycle from precipitation to runoff and infiltration.
Transformations: Transformations involve a change in the chemical nature of matter. For instance, nitrogen fixation converts atmospheric nitrogen (N₂) into ammonia (NH₃) by bacteria, making nitrogen available for plants.

2.3.3 Organisms, crude oil and natural gas contain organic stores of carbon. Inorganic stores can be found in the atmosphere, soils and oceans.

Explain what is meant by the term "residence time" in the context of the carbon cycle
Outline the differences between carbon stored in living organisms and carbon stored in the atmosphere.

Carbon is one of the most important elements on Earth, forming the basis of all living organisms. Despite advances in the energy sector, the majority of our energy needs are still met through the combustion of fossil fuels—oil, coal, and natural gas—which releases carbon dioxide (CO₂) into the environment..

Carbon is stored in organisms and forests, the atmosphere, soil, fossil fuels, and in the oceans. —Places where carbon is stored are called Carbon Sinks —The oceans are the largest carbon sinks, holding many times more carbon than all the forests on earth combined. —Climate change is affecting how much carbon the ocean can hold.

Organic and Inorganic Carbon Stores

Organic Carbon Stores:
- Organisms: Living organisms, including plants, animals, and microorganisms, store carbon in organic molecules such as carbohydrates, lipids, proteins, and nucleic acids. These organisms take in carbon during processes like photosynthesis and release it through respiration and decomposition.
- Crude Oil and Natural Gas: These fossil fuels are ancient organic carbon stores formed from the remains of plants and animals that lived millions of years ago. They contain carbon in the form of hydrocarbons, which release carbon dioxide (CO₂) when burned.
- Soil Organic Matter: Dead plant and animal material decomposes into organic matter in soils, storing carbon for varying lengths of time depending on environmental conditions and decomposition rates.
Inorganic Carbon Stores:
- Atmosphere: Carbon dioxide (CO₂) is the primary inorganic form of carbon in the atmosphere. It is a key greenhouse gas, influencing Earth's climate by trapping heat.
- Soils: Inorganic carbon can be found in soils in the form of carbonates, such as calcium carbonate (CaCO₃). These compounds are formed through weathering processes and can be stable for long periods.
- Oceans: The oceans store large amounts of inorganic carbon in the form of dissolved CO₂, bicarbonate (HCO₃⁻), and carbonate ions (CO₃²⁻). The ocean acts as a major carbon sink, absorbing CO₂ from the atmosphere. Oceans contain around 38,000 Gt of dissolved carbon. Oceans absorb about 20% of the carbon dioxide (CO₂) released into the atmosphere each year.
  - Physical Dissolution:
    - CO₂ molecules from the atmosphere dissolve in seawater.
    - This process forms carbonic acid.
  - Biological Uptake:
    - Marine organisms such as phytoplankton and algae use CO₂ for photosynthesis.
    - CO₂ is incorporated into the biomass of these organisms.

Equilibrium and Residence Time

Equilibrium: A carbon store is in equilibrium when the rate of carbon absorption (input) is balanced by the rate of carbon release (output). This balance is crucial for maintaining stable levels of carbon in different reservoirs and for overall climate stability.
Residence Time: Residence time refers to the average period that a carbon atom remains in a particular store before moving to another. It is an important concept for understanding the dynamics of the carbon cycle.
Short Residence Times: Carbon in the atmosphere, plants, and soils typically has short residence times, ranging from days to years. For example, carbon dioxide in the atmosphere can be taken up by plants during photosynthesis and released back through respiration relatively quickly.
Long Residence Times: Carbon in fossil fuels like crude oil and natural gas has very long residence times, measured in hundreds of millions of years. These carbon stores remain stable over geological timescales unless disturbed by human activities such as mining and combustion.

https://www.geomon.co.uk/carbon-storage-in-ecosystems/

the carbon cycle

2.3.4 Carbon flows between stores in ecosystems by photosynthesis, feeding, defecation, cellular
respiration, death and decomposition.

Outline the different flows in the carbon cycles
Identify where carbon is stored
Define carbon fixation
Define carbon budget

The carbon cycle involves the processes of photosynthesis and respiration. Carbon dioxide plays an important role in photosynthesis. Plants use energy from light to split water molecules; they then use carbon dioxide to synthesize carbohydrates. One of the products of this reaction is oxygen. Photosynthesis is the major source of oxygen in Earth’s atmosphere. For some 1.5 billion years before green plants were on Earth, algae and bacteria provided the photosynthesis needed to build Earth’s oxygen levels to the point that respiration of both plants and animals could occur.

Key Processes in Carbon Flows:

Photosynthesis:
- Plants and other photosynthetic organisms absorb carbon dioxide (CO₂) from the atmosphere and convert it into organic compounds, such as glucose, using the energy from sunlight. This process stores carbon in plant biomass and forms the basis of the food web.
Feeding:
- When animals consume plants or other organisms, they transfer the stored carbon into their own bodies. This carbon is then used for growth, energy, and reproduction, moving through the food chain.
Defecation:
- Not all consumed carbon is assimilated; some is excreted as waste. This process returns carbon to the soil, where it can be used by decomposers or contribute to soil organic matter.
Cellular Respiration:
- Both plants and animals release CO₂ back into the atmosphere through cellular respiration, a process that breaks down organic compounds to produce energy. This is a key transformation in the carbon cycle.
Combustion
- From energy technologies (not pictured) to atmosphere Humans transform coal, oil, and natural gas by burning, releasing carbon dioxide into the atmosphere
Fossilisation
- From soil to coal deposits, oil deposits, and natural gas deposits Organic matter under pressure transforms into coal deposits, oil deposits, and natural gas deposits.
Sedimentation
- From aquatic environments
  to coal deposits, oil deposits, and natural gas deposits Organic matter settles to the floor forming sediment. Under pressure this transforms into coal deposits, oil deposits, and natural gas deposits.
Death and Decomposition:
- When organisms die, their bodies are broken down by decomposers, such as bacteria and fungi. This decomposition process converts organic carbon back into inorganic forms, releasing CO₂ and other compounds into the soil and atmosphere.

If photosynthesis exceeds respiration in an ecosystem there is a net uptake of carbon dioxide, and if respiration exceeds photosynthesis there is a net release of carbon dioxide.

The Global Carbon Cycle

The carbon cycle is a natural process in which carbon moves between different stores and flows. It is maintained in a dynamic equilibrium, meaning that the amount of carbon absorbed into the stores is balanced by the amount of carbon released. Human activities have significantly affected the residence time in many carbon stores. For instance, by burning fossil fuels, we have released carbon into the atmosphere that would have otherwise been locked away in oil, coal, and gas reserves for millions of years.

https://www.e-education.psu.edu/earth103/node/1019

Carbon Cycle Animation

Application of skills: Create a systems diagram of the carbon cycle.

Systems Diagrams of the Carbon Cycle:

Understanding the carbon cycle involves visualizing how carbon flows between different stores in ecosystems. Systems diagrams are useful tools for representing these flows and highlighting the distinctions between transfers and transformations.

Transfers:
- Transfers involve the movement of carbon from one store to another without changing its form. For example, the transfer of carbon from plants to herbivores through feeding is a direct movement of organic carbon.
- Another example is the movement of carbon from the atmosphere to the ocean through the process of CO₂ dissolution.
Transformations:
- Transformations involve changes in the chemical form of carbon as it moves between stores. Photosynthesis and cellular respiration are key transformations in the carbon cycle.
- During photosynthesis, CO₂ is transformed into organic compounds like glucose. In cellular respiration, these organic compounds are broken down, releasing CO₂ back into the atmosphere.

A systems diagram of the carbon cycle typically includes the following components:

Atmospheric CO₂: The primary inorganic store of carbon in the atmosphere.
Plant Biomass: A major organic store of carbon, representing carbon fixed through photosynthesis.
Animals: Representing carbon transfers through feeding.
Soil Organic Matter: Including carbon from defecation, death, and decomposition.
Decomposers: Organisms that transform dead organic matter into inorganic forms.

2.3.5 Carbon sequestration is the process of capturing gaseous and atmospheric carbon dioxide and storing it in a solid or liquid form.

Define carbon sequestration
Describe how trees naturally sequester carbon through the process of photosynthesis.
Identify and describe two human-enhanced methods of carbon sequestration.

Life processes continually move carbon between different stores in what is known as the global carbon cycle. A carbon store, or storage, is an area where carbon accumulates over time through carbon sequestration. Carbon sequestration is the process of capturing gaseous and atmospheric carbon dioxide and storing it in a solid or liquid form, thereby reducing the amount of greenhouse gases in the atmosphere. Natural processes, such as the growth of trees and the formation of fossil fuels, play a significant role in carbon sequestration.

https://en.wikipedia.org/wiki/File:Carbon_sequestration-2009-10-07.svg

Tree Growth and Forest Ecosystems:

Photosynthesis:
- Trees and other vegetation absorb CO₂ from the atmosphere during photosynthesis.
- CO₂ is converted into organic compounds, such as glucose, which are used to build plant tissues.
Biomass Storage:
- The carbon absorbed by trees is stored in their biomass, including trunks, branches, leaves, and roots.
- Forests act as significant carbon sinks, sequestering large amounts of CO₂ over their lifetimes.
Soil Carbon:
- Dead plant material, such as leaves and branches, decomposes and contributes to soil organic matter.
- Soil stores carbon as organic matter, which can remain in the soil for long periods.

Formation of Fossil Fuels:

Organic Matter Burial:
- Over millions of years, dead plants and microorganisms accumulate in sediment layers.
- These organic materials are buried under sediments, where they are subjected to high pressure and temperature.
Fossilization:
- The buried organic matter gradually transforms into fossil fuels, such as coal, oil, and natural gas.
- This process effectively locks away carbon in a stable, long-term form.

Importance of Natural Carbon Sequestration

Climate Regulation:
- Natural carbon sequestration helps regulate the global climate by reducing atmospheric CO₂ levels.
- Forests and other ecosystems play a vital role in balancing the carbon cycle and mitigating the effects of climate change.
Biodiversity and Ecosystem Health:
- Healthy, carbon-sequestering ecosystems support diverse plant and animal species.
- Maintaining and restoring these ecosystems contributes to overall ecological health and resilience.

Case Study: Carbon Sequestration Capabilities of Various Forest Types in the Pacific Northwest

https://databasin.org/datasets/5e106e515eaf4b7f87053455fd7eb197/

https://www.climatehubs.usda.gov/hubs/northwest/topic/northwest-forests-and-woodlands

Introduction

Forests in the Pacific Northwest are renowned for their rich biodiversity and significant carbon sequestration capabilities. This case study assesses the carbon sequestration potential of different forest types in this temperate region, focusing on their role in capturing and storing atmospheric carbon dioxide (CO₂).

Forest Types Studied

Deciduous Forests:
- Dominated by broadleaf trees such as maple, alder, and oak.
- Known for high species diversity and seasonal leaf shedding.

Coniferous Forests:

Composed mainly of evergreen trees like Douglas fir, Western hemlock, and Sitka spruce.
Characterized by large, long-lived trees with high biomass.

Mixed Forests:

Contain a combination of deciduous and coniferous species.
Provide structural complexity and varied carbon sequestration dynamics.

2.3.6 Ecosystems can act as stores, sinks or sources of carbon.

Define the terms "carbon sink," "carbon store," and "carbon source"
Describe the role of a mature forest as a carbon store and explain how it maintains equilibrium
Compare and contrast the carbon dynamics in a young forest and a forest destroyed by fire.

Ecosystems play a crucial role in the global carbon cycle by acting as stores, sinks, or sources of carbon. The balance between carbon inputs (such as photosynthesis) and outputs (such as respiration) determines whether an ecosystem accumulates or releases carbon. Understanding these dynamics helps in managing ecosystems to mitigate climate change.

Stores, Sinks, and Sources of Carbon

Stores (Storages):
- Ecosystems that maintain a balance between carbon inputs and outputs over long periods act as carbon stores. These ecosystems hold carbon in stable forms, such as biomass and soil organic matter, without significant net accumulation or release.
Sinks:
- An ecosystem functions as a carbon sink when it absorbs more carbon dioxide (CO₂) than it releases. This net uptake of CO₂ typically occurs when photosynthesis rates exceed cellular respiration rates. Carbon sinks are crucial for reducing atmospheric CO₂ levels and mitigating climate change.
Sources:
- An ecosystem acts as a carbon source when it releases more CO₂ than it absorbs. This net release occurs when cellular respiration and decomposition rates exceed photosynthesis rates. Carbon sources contribute to increased atmospheric CO₂ levels, exacerbating climate change.

Carbon Dynamics in Different Ecosystems

Young Forest as a Carbon Sink:
- Photosynthesis vs. Respiration: In young forests, trees and vegetation are in a rapid growth phase, with high rates of photosynthesis. This high photosynthetic activity leads to a significant uptake of CO₂ from the atmosphere.
- Net Uptake: Since photosynthesis exceeds cellular respiration, young forests act as carbon sinks, sequestering large amounts of carbon in their biomass as they grow.
Mature Forest as a Carbon Store:
- Equilibrium: In mature forests, the rates of photosynthesis and cellular respiration are relatively balanced. The carbon absorbed through photosynthesis is approximately equal to the carbon released through respiration and decomposition.
- Stable Storage: This equilibrium means that mature forests act as carbon stores, holding large amounts of carbon in their biomass and soil organic matter without significant net accumulation or release.
Forest Destroyed by Fire or Deforestation as a Carbon Source:
- Increased CO₂ Release: When a forest is destroyed by fire or deforestation, the carbon stored in the biomass is rapidly released into the atmosphere as CO₂. The destruction of vegetation also reduces the capacity for photosynthesis, further reducing CO₂ uptake.
- Net Release: The immediate and substantial release of CO₂ from burning or decaying organic matter, coupled with reduced photosynthesis, turns the forest into a significant carbon source.

Factors Influencing Ecosystem Carbon Balance

Climate: Temperature and precipitation patterns affect photosynthesis and respiration rates, influencing whether an ecosystem acts as a carbon sink, store, or source.
Disturbances: Natural disturbances (e.g., fires, storms) and human activities (e.g., deforestation, land-use changes) can shift ecosystems from being carbon sinks or stores to sources.
Ecosystem Type: Different ecosystems (e.g., forests, grasslands, wetlands) have varying capacities for carbon storage and sequestration based on their biological and physical characteristics.

2.3.7 Fossil fuels are stores of carbon with unlimited residence times. They were formed when ecosystems acted as carbon sinks in past eras and become carbon sources when burned.

Outline the process by which fossil fuels become carbon sources when burned.
Explain the role of fossil fuels as carbon stores.
Explain the concept of residence time and discuss why the residence time of carbon in fossil fuels is considered unlimited.

Fossil fuels, including coal, oil, and natural gas, are significant carbon stores with extremely long residence times. These fuels were formed from ancient ecosystems that acted as carbon sinks, capturing and storing carbon over millions of years. Today, fossil fuels become major carbon sources when burned, releasing stored carbon dioxide (CO₂) into the atmosphere and contributing to climate change.

Fossil Fuels as Carbon Stores

Nature of Fossil Fuels:
- Fossil fuels are composed of carbon-rich organic materials derived from the remains of plants and microorganisms that lived millions of years ago.
- These fuels are stored deep within the Earth's crust, where they have remained relatively stable and isolated from the atmosphere, effectively sequestering carbon for geological timescales.
Residence Time:
- The residence time of carbon in fossil fuels is virtually unlimited, spanning hundreds of millions of years. This prolonged storage period is due to the deep burial and geological processes that preserve these carbon-rich deposits.
- Unlike the relatively short residence times of carbon in living organisms or the atmosphere, fossil fuels serve as long-term carbon reservoirs.
Formation and Storage:
- Fossil fuels were formed in past geological eras when large amounts of organic material were buried and subjected to heat and pressure over millions of years. This process transformed the organic material into coal, oil, and natural gas.
- During their formation, ancient ecosystems acted as carbon sinks, absorbing CO₂ from the atmosphere and storing it in organic matter. This carbon was eventually locked away in fossil fuel deposits.

https://serc.carleton.edu/details/images/65244.html

Fossil Fuels as Carbon Sources

Burning Fossil Fuels:
- When fossil fuels are extracted and burned for energy, the stored carbon is released back into the atmosphere as CO₂. This release converts fossil fuels from long-term carbon stores to significant carbon sources.
- The combustion of fossil fuels is a major contributor to the increase in atmospheric CO₂ levels, driving global warming and climate change.
Impact on the Carbon Cycle:
- The large-scale burning of fossil fuels disrupts the natural carbon cycle by introducing vast amounts of CO₂ that were previously sequestered for millions of years. This rapid release of carbon overwhelms natural carbon sinks, such as forests and oceans, leading to an accumulation of CO₂ in the atmosphere.
- This imbalance in the carbon cycle exacerbates the greenhouse effect, resulting in higher global temperatures and associated climatic changes.

effects of human activity on carbon cycle

2.3.8 Agricultural systems can act as carbon stores, sources and sinks, depending on the techniques
used.

Explain how crop rotation can enhance the role of soil as a carbon sink.
Outline the benefits of cover cropping for soil carbon sequestration.
Describe the impact of heavy tillage on soil carbon storage and CO₂ emissions.

Human Impact on Carbon Stores

Human activities have significantly altered the natural equilibrium of carbon stores. One of the main sources of these carbon dioxide emissions is the extraction and combustion of fossil fuels:

Burning Fossil Fuels: The combustion of crude oil, natural gas, and coal releases large amounts of CO₂ into the atmosphere, rapidly depleting ancient carbon stores and increasing atmospheric CO₂ levels, contributing to global warming.

Agriculture is another human activity that disturbs the carbon cycle.
Agricultural systems can function as carbon stores, sources, or sinks depending on the farming techniques employed. Sustainable and regenerative agricultural practices enhance the soil’s capacity to sequester carbon, while conventional practices can lead to increased carbon emissions.

Agricultural systems act as carbon stores when they maintain a balance between carbon inputs (e.g., plant residues, organic fertilizers) and outputs (e.g., CO₂ emissions from soil respiration). An agricultural system functions as a carbon sink when it absorbs more CO₂ from the atmosphere than it releases. This is typically achieved through practices that increase soil organic matter and enhance plant growth

Agricultural practices such as no-till farming, cover cropping, and agroforestry can enhance soil carbon sequestration by increasing organic matter inputs to the soil and reducing soil erosion

No-Till Farming: No-till agriculture involves planting crops directly into the soil without disturbing it with tillage implements. This method reduces soil erosion and allows organic matter to accumulate on the soil surface.
- Benefits: No-till farming helps maintain soil structure, reduces erosion, and increases water retention. The accumulation of organic matter enhances carbon storage in the soil.
- Example: An image of soybeans growing in the residue from a wheat crop illustrates how no-till farming retains organic matter from previous crops.

https://www.agri-pulse.com/articles/16869-cover-crops-can-benefit-farmers-earth-in-many-ways

Cover Cropping: Cover crops are planted between cash crops to protect the soil from erosion, suppress weeds, and add organic matter. Common cover crops include radishes, clover, and rye.
- Benefits: Cover crops prevent soil erosion, improve soil structure, and enhance soil fertility. The decaying cover crops enrich the soil with carbon, contributing to long-term carbon sequestration.
- Example: An image of radishes used as a cover crop shows how these plants protect the soil and add organic matter.

Crop Rotation: Crop rotation involves growing different types of crops in the same area in sequential seasons. Rotating crops with different root structures and nutrient needs helps break up compacted soil and prevent nutrient depletion.
- Benefits: This practice improves soil structure, increases biodiversity, and enhances nutrient cycling. Healthy soil structure can hold more organic matter, acting as a carbon sink.
- Example: Rotating legumes with grains can improve soil nitrogen levels and organic matter content.

https://canadianfoodfocus.org/on-the-farm/crop-rotations-ensure-a-sustainable-future-for-agriculture/

Agroforestry: Agroforestry integrates trees and shrubs into agricultural landscapes, combining agriculture and forestry practices.
- Benefits: Trees and shrubs sequester carbon in their biomass and root systems, improve soil structure, and provide additional organic matter. Agroforestry systems enhance biodiversity and resilience to climate change.
- Example: Planting fruit trees alongside crops can provide both carbon sequestration benefits and economic returns for farmers.

https://www.usda.gov/media/blog/2020/08/21/promoting-pollinators-agroforestry

Impact on Soil Health and Carbon Sequestration:

These sustainable agricultural practices not only sequester carbon but also improve overall soil health. Increased organic matter in the soil enhances soil fertility, water retention, and resilience to environmental stresses. By adopting these practices, farmers can contribute to climate change mitigation while maintaining productive and sustainable agricultural systems.

2.3.9 Carbon dioxide is absorbed into the oceans by dissolving and is released as a gas when it comes out of a solution.

Describe the process by which carbon dioxide is absorbed into the oceans.
Outline the role of oceans as a carbon sink and discuss the factors that influence the rate of CO₂ absorption
Describe the process by which carbon dioxide is absorbed into the oceans.

https://nautil.us/how-seawater-might-soak-up-more-carbon-261446/

The oceans play a vital role in the global carbon cycle by acting as a major carbon sink, absorbing and storing significant amounts of carbon dioxide (CO₂) from the atmosphere. However, the rate at which human activities, particularly the burning of fossil fuels, release CO₂ exceeds the oceans' capacity to absorb it, leading to increased atmospheric CO₂ levels and contributing to climate change.

Carbon Dioxide Absorption and Release in Oceans

Absorption of CO₂:

Dissolution Process:
- CO₂ from the atmosphere dissolves in seawater, forming carbonic acid (H₂CO₃).
- This process is driven by the concentration gradient between atmospheric CO₂ and dissolved CO₂ in the ocean.
- The dissolved CO₂ can further dissociate into bicarbonate (HCO₃⁻) and carbonate ions (CO₃²⁻), which are more stable forms of inorganic carbon in seawater.
Biological Uptake:
- Photosynthesis:
  - Marine organisms, such as phytoplankton and algae, absorb dissolved CO₂ for photosynthesis.
  - These organisms convert CO₂ into organic matter, incorporating it into their biomass.
  - This process effectively removes CO₂ from the water, allowing more atmospheric CO₂ to dissolve.

Release of CO₂:

Outgassing:
- When the concentration of dissolved CO₂ in seawater exceeds the equilibrium with the atmosphere, CO₂ is released back into the air.
- This release occurs naturally through processes such as oceanic circulation and temperature changes, which affect the solubility of CO₂ in water.

Oceans as a Carbon Sink

Role as a Carbon Sink:
- Oceans absorb approximately 20% of the CO₂ emitted by human activities annually.
- The vast surface area and volume of the oceans provide a significant capacity for CO₂ absorption and storage.
Limitation of Absorption:
- Despite their role as a carbon sink, the rate of CO₂ absorption by the oceans is limited by factors such as water temperature, ocean circulation patterns, and the capacity of marine ecosystems.
- Warmer water holds less CO₂, reducing the effectiveness of the oceans as a carbon sink in a warming climate.

2.3.10 Increases in concentrations of dissolved carbon dioxide cause ocean acidification, harming marine animals.

Explain the chemical process of ocean acidification
Describe how increased concentrations of dissolved CO₂ affect the pH of seawater..
Explain the impact of ocean acidification on the ability of marine organisms to form calcium carbonate shells and skeletons.

https://www.researchgate.net/figure/Schematic-diagram-of-ocean-acidification-The-reaction-between-dissolved-carbon-dioxide_fig1_319405916

Ocean acidification is a significant consequence of increased concentrations of dissolved carbon dioxide (CO₂) in seawater. As more CO₂ is absorbed by the oceans, it leads to chemical reactions that lower the pH of seawater, making it more acidic. This acidification has harmful effects on marine life, particularly on organisms that rely on calcium carbonate for their shells and skeletons, such as molluscs and corals.

Process of Ocean Acidification

Dissolution of CO₂:
- CO₂ from the atmosphere dissolves in seawater, forming carbonic acid (H₂CO₃).
- Carbonic acid dissociates into bicarbonate (HCO₃⁻) and hydrogen ions (H⁺).
- The increase in hydrogen ions leads to a decrease in pH, making the water more acidic.
Chemical Reactions:
- The formation of bicarbonate and hydrogen ions reduces the availability of carbonate ions (CO₃²⁻), which are essential for calcium carbonate (CaCO₃) formation.
- Calcium carbonate is crucial for the development of shells and skeletons in many marine organisms

https://ugc.berkeley.edu/background-content/ocean-acidification/

https://mindthegraph.com/blog/ocean-acidification-consequences/

Impact on Marine Life

Harm to Molluscs:
- Molluscs, such as clams, oysters, and snails, rely on calcium carbonate to build their shells.
- Ocean acidification reduces the availability of carbonate ions needed for shell formation.
- As a result, molluscs experience thinner, weaker shells, making them more vulnerable to predators and environmental stresses.
Harm to Corals:
- Corals use calcium carbonate to construct their skeletons, forming the structure of coral reefs.
- Lower pH levels interfere with the corals' ability to produce and maintain their calcium carbonate skeletons.
- This results in slower growth rates, weakened structural integrity, and increased susceptibility to damage and disease.

Broader Ecosystem Effects:

Many marine organisms, including some species of plankton and fish, are affected by changes in pH and carbonate ion availability.
The disruption of shell and skeleton formation can lead to declines in populations of key species, affecting the entire marine food web.
Coral reefs, which provide habitat and protection for numerous marine species, face degradation and loss, impacting biodiversity and coastal ecosystems.

Case Study: Effects of Ocean Acidification on Coral Reefs in the Great Barrier Reef

https://www.cruisemapper.com/ports/great-barrier-reef-port-646#google_vignette

Introduction

The Great Barrier Reef (GBR), located off the coast of Queensland, Australia, is the world's largest coral reef system and a UNESCO World Heritage site. It spans over 2,300 kilometers and is home to thousands of marine species, making it a critical habitat for marine biodiversity. However, this iconic ecosystem faces significant threats from ocean acidification, driven by increased atmospheric CO₂ levels.

Sources: Ocean pH and Atmospheric CO₂ Levels: Doney, S. C., Fabry, V. J., Feely, R. A., & Kleypas, J. A. (2009). Ocean Acidification: The Other CO2 Problem. Annual Review of Marine Science, 1, 169-192. Feely, R. A., Doney, S. C., & Cooley, S. R. (2009). Ocean acidification: Present conditions and future changes in a high-CO2 world. Oceanography, 22(4), 36-47. Coral Calcification Rates: De'ath, G., Lough, J. M., & Fabricius, K. E. (2009). Declining Coral Calcification on the Great Barrier Reef. Science, 323(5910), 116-119. Coral Bleaching Events: Hughes, T. P., Kerry, J. T., Álvarez-Noriega, M., Álvarez-Romero, J. G., Anderson, K. D., Baird, A. H., ... & Wilson, S. K. (2017). Global warming and recurrent mass bleaching of corals. Nature, 543(7645), 373-377.

Impact of Acidification:

Calcification:
- Lower pH levels reduce the availability of carbonate ions, which are essential for coral calcification. This weakens coral skeletons and hampers growth.
Bleaching:
- Acidification, combined with rising sea temperatures, stresses corals, leading to more frequent and severe bleaching events.
Biodiversity Loss:
- As corals struggle to maintain their skeletons, the structure of the reef deteriorates, leading to habitat loss for many marine species.

Ecosystem Services at Risk:

Coastal Protection:
- Coral reefs act as natural barriers against storms and erosion. Degraded reefs are less effective, increasing vulnerability for coastal communities.
Fisheries:
- Many fish species depend on healthy coral reefs for spawning and feeding. A decline in reef health can reduce fish populations and impact local fisheries.
Tourism:
- The Great Barrier Reef is a major tourist attraction. Coral degradation can reduce its appeal, affecting tourism revenue.

2.3.11 Measures are required to alleviate the effects of human activities on the carbon cycle.

Define low-carbon technologies and explain how they contribute to mitigating the effects of human activities on the carbon cycle
Explain the process of carbon capture and storage (CCS) and its role in reducing atmospheric CO₂ levels.
Outline the environmental benefits of reforestation in terms of carbon sequestration.

Human activities, such as burning fossil fuels, deforestation, and soil disruption, have significantly altered the carbon cycle, leading to increased atmospheric CO₂ levels and contributing to climate change. To mitigate these effects, various measures must be implemented to reduce carbon emissions and enhance carbon sequestration. This section explores several key strategies, including low-carbon technologies, reduction of fossil fuel use, reforestation, and artificial carbon sequestration.

Low-Carbon Technologies:

Renewable Energy Sources:
- Description: Transitioning to renewable energy sources such as solar, wind, hydro, and geothermal power can significantly reduce CO₂ emissions.
- Benefits: These technologies generate electricity without burning fossil fuels, thus lowering greenhouse gas emissions and reducing dependence on non-renewable resources.
- Example: Solar panels convert sunlight directly into electricity, while wind turbines harness wind energy to generate power.
Energy Efficiency:
- Description: Implementing energy-efficient technologies and practices in industries, transportation, and buildings reduces overall energy consumption and CO₂ emissions.
- Benefits: Energy efficiency minimizes the demand for energy from fossil fuels, cutting down emissions and lowering energy costs.
- Example: LED lighting, high-efficiency appliances, and improved insulation in buildings contribute to significant energy savings.

Reduction in Use

Fossil Fuel Reduction:
- Description: Reducing the burning of fossil fuels for energy production and transportation is crucial for decreasing CO₂ emissions.
- Benefits: Lowering fossil fuel use reduces the release of greenhouse gases and mitigates climate change.
- Example: Promoting electric vehicles and public transportation reduces reliance on gasoline and diesel engines.
Minimizing Soil Disruption:
- Description: Sustainable agricultural practices that minimize soil disruption help maintain soil carbon stores and reduce CO₂ emissions.
- Benefits: Practices such as no-till farming and cover cropping prevent soil erosion, enhance soil health, and increase carbon sequestration in soils.
- Example: No-till farming involves planting crops without disturbing the soil, which helps retain soil organic matter and carbon.
Deforestation Reduction:
- Description: Preventing deforestation and promoting sustainable forest management are essential for maintaining carbon stores in forests.
- Benefits: Forests act as significant carbon sinks, and protecting them helps preserve their carbon sequestration capacity.
- Example: Implementing policies to curb illegal logging and promoting sustainable forestry practices ensure that forests continue to absorb CO₂.

Carbon Capture

Reforestation:
- Description: Reforestation involves planting trees on degraded or deforested lands to restore forest cover and enhance carbon sequestration.
- Benefits: Trees absorb CO₂ from the atmosphere and store carbon in their biomass, contributing to long-term carbon sequestration and ecosystem restoration.
- Example: The Bonn Challenge aims to restore 350 million hectares of deforested and degraded landscapes by 2030, enhancing global carbon sequestration efforts.

Artificial Carbon Sequestration:
- Description: Artificial carbon sequestration technologies capture CO₂ emissions from industrial sources and store them underground in geological formations.
- Benefits: This process prevents CO₂ from entering the atmosphere and contributes to reducing greenhouse gas concentrations.
- Example: Carbon capture and storage (CCS) involves capturing CO₂ from power plants and industrial facilities and injecting it into

Biochar:
Biochar is a stable form of carbon created from organic matter through a process called pyrolysis, which involves heating the material in the absence of oxygen. This process not only converts organic matter into a carbon-rich, porous substance but also has significant benefits for soil fertility and carbon storage. Biochar is increasingly recognized as a valuable tool for sustainable agriculture and climate change mitigation.

Benefits of Biochar:
- Enhanced Nutrient Retention: Biochar’s porous structure improves the soil’s ability to retain nutrients and water, making them more available to plants. This reduces the need for chemical fertilizers and enhances plant growth.
- Increased Microbial Activity: The porous nature of biochar provides habitats for soil microorganisms, which play crucial roles in nutrient cycling and soil health.
- pH Regulation: Biochar can help neutralize acidic soils, improving growing conditions for many crops.
- Long-Term Sequestration: By converting organic waste into biochar, carbon is locked into a stable form that resists degradation. This prevents the carbon from being released back into the atmosphere as CO₂, contributing to long-term carbon sequestration.
- Climate Change Mitigation: The use of biochar in soils not only sequesters carbon but also reduces greenhouse gas emissions from soils, such as nitrous oxide (N₂O) and methane (CH₄), which are potent greenhouse gases.

Environmental Benefits:
- Waste Management: Biochar production provides a sustainable way to manage agricultural and forestry waste, converting it into a valuable resource.
- Soil Health: Improved soil structure and fertility contribute to enhanced crop yields and resilience against environmental stressors such as drought and erosion.

Applications of Biochar:
- Agricultural Use: Biochar is widely used in farming to improve soil fertility, enhance crop yields, and reduce the need for chemical inputs. It is particularly beneficial in degraded soils and regions facing soil fertility challenges.
- Reclamation Projects: Biochar is used in land reclamation projects to restore soil health and productivity in degraded lands, such as former mining sites and deforested areas.
- Gardening and Landscaping: Home gardeners and landscapers use biochar to improve soil quality, increase plant growth, and enhance the aesthetic value of gardens and green spaces.

hl only

carbon stores in the lithosphere

2.3.12 The lithosphere contains carbon stores in fossil fuels and in rocks, such as limestone, that contain calcium carbonate.

Define the term 'lithosphere'
Explain the significance of the lithosphere in the carbon cycle.

The lithosphere, the outermost layer of the Earth, plays a crucial role in the global carbon cycle by storing vast amounts of carbon in fossil fuels and rocks. These carbon stores have exceptionally long residence times, spanning hundreds of millions of years, making the lithosphere a significant carbon reservoir.

Carbon Stores in the Lithosphere

Fossil Fuels:
- Types: Includes coal, oil, and natural gas.
- Formation: Formed from the remains of ancient plants and microorganisms that were buried and subjected to heat and pressure over millions of years.
- Carbon Content: Fossil fuels are rich in carbon, which is released as CO₂ when they are burned for energy.
- Residence Time: The carbon in fossil fuels has been stored for hundreds of millions of years, locked away from the carbon cycle until extracted and combusted by humans.

Carbonate Rocks:
- Limestone and Dolomite: These rocks contain significant amounts of calcium carbonate (CaCO₃).
- Formation: Formed from the accumulation of shell, coral, algal, and fecal debris in marine environments, or by direct precipitation from seawater.
- Carbon Storage: Carbonate rocks are one of the largest carbon reservoirs on Earth, storing carbon in a stable form.
- Residence Time: Carbon stored in carbonate rocks also has a residence time of hundreds of millions of years, making it a long-term carbon sink.

Importance of Lithospheric Carbon Stores
The carbon stored in the lithosphere plays a crucial role in regulating Earth's climate over geological timescales.
The slow release of carbon from these stores, through processes like weathering and volcanic activity, contributes to the natural balance of the carbon cycle.

2.3.13 Reef-building corals and molluscs have hard parts that contain calcium carbonate that can
become fossilized in limestone.

Explain how reef-building corals contribute to carbon storage in the lithosphere.
Describe the role of molluscs in the formation of limestone.
Outline the process of fossilization of calcium carbonate structures in corals and molluscs
Discuss the significance of limestone as the largest carbon store in Earth systems.

Reef-building corals and molluscs are vital components of marine ecosystems, and they play a significant role in the global carbon cycle. These organisms have hard parts composed of calcium carbonate (CaCO₃), which can become fossilized in limestone. Limestone, formed through various processes, is the largest store of carbon in Earth's systems.

Calcium Carbonate Structures:

Corals:
- Reef-building corals secrete calcium carbonate to form their skeletons.
- These skeletal structures create complex reef systems that provide habitat for a diverse array of marine life.
Molluscs:
- Molluscs, such as clams, oysters, and snails, also produce shells made of calcium carbonate.
- These shells can accumulate on the ocean floor, contributing to sediment formation.

Fossilization Process:

Over time, the calcium carbonate structures of corals and molluscs can become buried by sediment.
Through geological processes, these sediments are compressed and cemented, forming limestone.
Fossilized remains of corals and molluscs are often found within limestone deposits, providing a historical record of marine life.

Limestone as a Carbon Store:

Limestone is the largest carbon store in Earth’s systems, holding a vast amount of carbon in a stable, solid form.
It plays a critical role in regulating atmospheric CO₂ levels over geological timescales.

Formation Processes:

Biological Processes:
- The fossilization of marine organisms like corals and molluscs is a key biological process in limestone formation.
Non-Biological Processes:
- Limestone can also form through chemical precipitation from water, without the direct involvement of living organisms.
- While the details of these processes are complex, they contribute significantly to the formation of limestone.

Importance of Limestone Carbon Storage:

Climate Regulation:
- The carbon stored in limestone is locked away for millions of years, effectively removing it from the carbon cycle.
- This long-term storage helps regulate atmospheric CO₂ levels and stabilize Earth’s climate.
Geological Carbon Cycle:
- Limestone formations are part of the geological carbon cycle, which involves the movement of carbon through the Earth’s crust.
- Weathering of limestone can release carbon slowly back into the atmosphere, balancing the carbon cycle over long periods.

2.3.14 In past geological eras, organic matter from partially decomposed plants became fossilized in coal, and partially decomposed marine organisms became fossilized in oil and natural gas held in porous rocks.

Describe the process of coal formation from partially decomposed plant matter.
Explain the conditions necessary for the formation of oil and natural gas from marine organisms.
Identify two geological periods when significant coal formation occurred and explain why these periods were conducive to coal formation

https://lms-leicester.libguides.com/c.php?g=807815

Fossil fuels, including coal, oil, and natural gas, are formed from the remains of ancient plants and marine organisms. These fuels are significant carbon stores, and their formation occurred over tens of millions of years during specific geological eras when conditions were particularly favorable.

Coal Formation:

Source Material:
- Partially decomposed plant matter, primarily from ancient forests and swamps.
Process:
- Over millions of years, layers of plant debris accumulated in wetlands.
- Burial under sediments caused the organic material to undergo physical and chemical changes, transforming it into peat.
- Further burial and increased pressure and temperature converted peat into lignite (brown coal), then into bituminous coal (soft coal), and finally into anthracite (hard coal).
Geological Eras:
- Major coal-forming periods include the Carboniferous Period (about 359 to 299 million years ago) and the Permian Period (about 299 to 252 million years ago).

Oil and Natural Gas Formation:

Source Material:
- Partially decomposed marine organisms, including plankton and algae.
Process:
- Organic matter from marine organisms settled on the ocean floor and mixed with sediments, forming organic-rich mud.
- Over millions of years, this mud was buried under additional sediments, increasing pressure and temperature.
- The organic material underwent chemical changes, transforming into kerogen (a waxy substance) and then into liquid oil and gaseous hydrocarbons (natural gas).
- Oil and natural gas migrated through porous rocks until trapped by impermeable rock layers, forming reservoirs.
Geological Eras:
- Significant oil and gas formation occurred during the Mesozoic Era (about 252 to 66 million years ago), particularly the Jurassic and Cretaceous periods, and the Cenozoic Era (about 66 million years ago to present).

Conditions Favorable for Fossil Fuel Formation:

High Organic Productivity:
- Periods with warm, humid climates and extensive vegetation growth led to high rates of organic matter production and accumulation.
- Marine environments with abundant plankton and algae also contributed to significant organic deposits.
Anaerobic Conditions:
- Low-oxygen environments, such as swamps and deep ocean floors, slowed the decomposition of organic material, allowing it to accumulate and eventually fossilize.
Sedimentation Rates:
- Rapid sedimentation buried organic material quickly, protecting it from complete decomposition and facilitating its transformation into fossil fuels.
Significance of Geological Eras:
- Carboniferous Period:
  - Known for extensive coal-forming forests and swamps.
  - Conditions were ideal for the formation of large coal deposits, with high organic productivity and rapid burial by sediments.
- Mesozoic Era:
  - Marked by high sea levels and warm climates, promoting the growth of marine plankton.
  - Significant oil and gas reserves formed during this time, especially in large sedimentary basins.
- Cenozoic Era:
  - Continued formation of oil and gas, particularly in newer sedimentary basins.
  - Advances in geological processes and tectonic activity created favorable conditions for fossil fuel accumulation.

2.3.15 Methane is produced from dead organic matter in anaerobic conditions by methanogenic bacteria.

Define methanogenesis and explain the role of methanogenic bacteria in this process.
Describe the conditions necessary for methanogenesis to occur
Discuss the significance of wetlands as natural sources of methane emissions

Methane (CH₄) is a potent greenhouse gas produced from the decomposition of organic matter in anaerobic (oxygen-free) conditions. This process, known as methanogenesis, is carried out by specialized microorganisms called methanogenic bacteria. Anaerobic conditions suitable for methanogenesis are found in various environments, including swamps, rice paddies, and the stomachs of ruminants like cattle.

Importance of Methane in the Carbon Cycle:

Greenhouse Gas:
- Methane is a potent greenhouse gas, with a global warming potential much higher than carbon dioxide (CO₂) over a 20-year period.
- Methane emissions contribute to the enhanced greenhouse effect and global warming.
Methane Oxidation:
- Methane released into the atmosphere is eventually oxidized to CO₂ and water vapor, completing its cycle in the carbon cycle.
- The residence time of methane in the atmosphere is relatively short, about 12 years, compared to CO₂.

Methanogenic Bacteria:

Role: These bacteria are responsible for breaking down organic matter in the absence of oxygen, producing methane as a byproduct.
Types: There are different types of methanogenic bacteria, each adapted to specific anaerobic environments.
Anaerobic Conditions: Methanogenesis occurs in environments where oxygen is absent or extremely limited. These conditions prevent the complete decomposition of organic matter, allowing methanogenic bacteria to thrive

Swamps and Wetlands:

Description: Swamps, wetlands, and marshes are waterlogged areas where organic matter accumulates.
Process: Dead plant material and other organic matter settle in the waterlogged soil, where anaerobic conditions prevent full decomposition. Methanogenic bacteria break down the organic matter, releasing methane into the atmosphere.
Impact: Wetlands are significant natural sources of methane emissions

Rice Paddies:

Description: Rice paddies are flooded agricultural fields where rice is grown.
Process: The standing water in rice paddies creates anaerobic conditions in the soil. As rice plants grow and decay, methanogenic bacteria decompose the organic matter, producing methane.
Impact: Rice cultivation is a major agricultural source of methane emissions.

https://water.unl.edu/article/manure-nutrient-management/reducing-carbon-footprint-cattle-operations-through-diet

Stomachs of Ruminants:

Description: Ruminants, such as cattle, sheep, and goats, have specialized stomachs (rumens) that allow them to digest fibrous plant material.
Process: In the rumen, anaerobic conditions enable methanogenic bacteria to break down cellulose and other complex carbohydrates, producing methane as a byproduct.
Impact: Livestock farming contributes significantly to global methane emissions due to enteric fermentation in ruminants.

2.3.16 Methane has a residence time of about 10 years in the atmosphere and is eventually oxidized to carbon dioxide

Define the term 'residence time' and explain its significance for methane in the atmosphere
Describe the oxidation process of methane in the atmosphere
Explain why methane is considered a potent greenhouse gas.

Methane (CH₄) is a potent greenhouse gas that plays a significant role in the Earth's atmosphere and climate system. Although its concentration in the atmosphere is much lower than that of carbon dioxide (CO₂), methane's impact on global warming is considerable due to its high global warming potential (GWP). Methane has a relatively short residence time in the atmosphere, approximately 10 years, after which it is oxidized to carbon dioxide.

Global Warming Potential (GWP):

Methane is about 25 times more effective than carbon dioxide at trapping heat in the atmosphere over a 100-year period.
This high GWP means that even small concentrations of methane can have a significant impact on global temperatures.

Sources of Methane:

Natural sources: Wetlands, termites, and oceans.
Anthropogenic sources: Agriculture (rice paddies, livestock), fossil fuel extraction and use, landfills, and biomass burning.

Residence Time

Methane has a residence time of approximately 10 years in the atmosphere.
During this time, methane molecules absorb infrared radiation, contributing to the greenhouse effect.
Eventually, methane is oxidized in the atmosphere through reactions with hydroxyl radicals (OH), converting it into carbon dioxide and water vapor.

Oxidation Process:

Hydroxyl Radicals (OH):
- The primary sink for atmospheric methane is its reaction with hydroxyl radicals.
- These radicals are highly reactive molecules formed in the atmosphere by the action of sunlight on water vapor and ozone.
Oxidation Reaction:
CH₄ + OH → CH₃ + H₂O
CH₃ + OH → CH₃O
CH₃O + O₂ → HCHO + HO₂
HO₂ + NO → NO₂ + OH
NO₂ + sunlight → NO + O
O + O₂ → O₃ (ozone)
HCHO (formaldehyde) eventually breaks down to CO₂ and H₂O

nitrogen cycle

2.3.17 The nitrogen cycle contains organic and inorganic stores.

Outline the organic and inorganic stores in the nitrogen cycle.

The nitrogen cycle is a crucial biogeochemical cycle that circulates nitrogen through the atmosphere, soil, water, and living organisms. Nitrogen is essential for the formation of proteins, nucleic acids, and other vital compounds in living organisms. The cycle includes both organic and inorganic nitrogen stores, each playing a vital role in maintaining ecosystem health and productivity.

Organic Nitrogen Stores

In Living Organisms:
- Proteins: Nitrogen is a key component of amino acids, the building blocks of proteins, which are essential for growth and cellular functions.
- Nucleic Acids: Nitrogen is found in the nucleotides that make up DNA and RNA, crucial for genetic information storage and transfer.
- Nitrogenous Compounds: Other nitrogen-containing compounds in living organisms include chlorophyll (for photosynthesis) and hormones.
In Dead Organic Matter:
- Decomposition: When plants and animals die, their organic nitrogen is broken down by decomposers (bacteria and fungi) into simpler organic compounds.
- Humus: Decomposed organic matter in soil, known as humus, contains nitrogen that can be further broken down into inorganic forms.

Inorganic Nitrogen Stores

In the Atmosphere:
- Nitrogen Gas (N₂): The atmosphere is composed of approximately 78% nitrogen gas, which is relatively inert and not directly usable by most living organisms.
- Nitrogen Fixation: Certain bacteria and industrial processes convert atmospheric nitrogen into forms that can be used by plants, such as ammonia (NH₃).
In Soil and Water:
- Ammonia (NH₃) and Ammonium (NH₄⁺): Produced by nitrogen-fixing bacteria, decomposers, and the Haber-Bosch process. These compounds can be taken up by plants or further converted.
- Nitrites (NO₂⁻) and Nitrates (NO₃⁻):
- Nitrification: Nitrifying bacteria convert ammonia into nitrites and then into nitrates.
- Assimilation: Plants absorb nitrates from the soil and use them to build organic molecules.
- Denitrification: Denitrifying bacteria convert nitrates back into nitrogen gas, completing the nitrogen cycle.

https://www.geeksforgeeks.org/diagram-of-nitrogen-cycle/

2.3.18 Bacteria have essential roles in the nitrogen cycle.

Describe the process of nitrification and explain the role of bacteria in this process.
Outline the process of denitrification and discuss its significance in the nitrogen cycle.

Bacteria play a crucial role in the nitrogen cycle, facilitating the transformation of nitrogen into various chemical forms that are essential for life. These microorganisms drive key processes in the nitrogen cycle, ensuring the availability of nitrogen for plants, animals, and other organisms. Without bacteria, the nitrogen cycle would not function effectively, and life as we know it would be severely impacted.

Key Roles of Bacteria in the Nitrogen Cycle

Nitrogen Fixation: Converts atmospheric nitrogen (N₂) into ammonia (NH₃), a form that can be utilized by plants.
- Bacteria Involved:
  - Free-Living Nitrogen-Fixing Bacteria: Such as Azotobacter and Clostridium, found in soil.
  - Symbiotic Nitrogen-Fixing Bacteria: Such as Rhizobium, which form nodules on the roots of leguminous plants (e.g., peas, beans).
- Process:
  - Nitrogen gas (N₂) is converted to ammonia (NH₃) by the enzyme nitrogenase.
  - Ammonia can then be taken up by plants and used to synthesize organic nitrogen compounds.
Nitrification: Converts ammonia (NH₃) into nitrites (NO₂⁻) and then into nitrates (NO₃⁻), which plants can absorb.
- Bacteria Involved:
  - Ammonia-Oxidizing Bacteria: Such as Nitrosomonas, convert ammonia into nitrites.
  - Nitrite-Oxidizing Bacteria: Such as Nitrobacter, convert nitrites into nitrates.
- Process:
  - Ammonia (NH₃) is oxidized to nitrite (NO₂⁻) by Nitrosomonas.
  - Nitrite (NO₂⁻) is further oxidized to nitrate (NO₃⁻) by Nitrobacter.
Assimilation: Plants and other organisms absorb nitrates (NO₃⁻) and incorporate them into organic molecules, such as amino acids and proteins.
- Bacteria Involved: While assimilation primarily occurs in plants and animals, soil bacteria play a role in maintaining the availability of nitrates.
Ammonification: Converts organic nitrogen from dead organisms and waste products back into ammonia (NH₃), returning nitrogen to the soil.
- Bacteria Involved:
  - Decomposers: Such as Bacillus and Pseudomonas, break down proteins and other nitrogen-containing organic compounds into ammonia.
- Process:
  - Organic nitrogen compounds are decomposed into ammonia by the action of decomposing bacteria.
Denitrification: Converts nitrates (NO₃⁻) back into nitrogen gas (N₂), releasing it into the atmosphere and completing the nitrogen cycle.
- Bacteria Involved:
  - Denitrifying Bacteria: Such as Pseudomonas and Clostridium, found in anaerobic conditions (e.g., waterlogged soils).
- Process:
  - Nitrate (NO₃⁻) is reduced to nitrite (NO₂⁻) and then to nitrogen gas (N₂) by denitrifying bacteria.
  - This process occurs in the absence of oxygen and is essential for balancing the nitrogen cycle.

2.3.19 Denitrification only happens in anaerobic conditions, such as soils that are waterlogged.

Define denitrification
Describe the conditions under which denitrification occurs.
Explain how insectivorous plants obtain nitrogen in anaerobic conditions

Denitrification is a crucial process in the nitrogen cycle that occurs under anaerobic (oxygen-free) conditions, such as in waterlogged soils. This process involves the conversion of nitrates (NO₃⁻) into nitrogen gas (N₂), which is then released into the atmosphere. Waterlogged, anaerobic soils present challenges for plant growth, but some plants have evolved unique adaptations to thrive in these conditions.

Impact on Soil and Plant Growth:

Denitrification reduces the availability of nitrates in the soil, limiting the nitrogen available for plant uptake.
Waterlogged soils create anaerobic conditions that hinder root respiration and nutrient uptake, leading to reduced plant growth or even plant death.

Adaptations of Insectivorous Plants

Plants that derive some or most of their nutrients by capturing and digesting insects and other small animals. Insectivorous plants have evolved to capture insects as an alternative nitrogen source, compensating for the low availability of soil nitrogen in waterlogged conditions.

https://www.ft.com/content/6b71cd84-4ff5-11e9-8f44-fe4a86c48b33

Pitcher Plants (genus Nepenthes and Sarracenia): Have modified leaves forming pitcher-shaped structures filled with digestive enzymes and fluids. Insects are attracted to the pitchers, fall in, and are digested.

Sundews (genus Drosera): Have glandular hairs on their leaves that secrete sticky substances to trap insects. The leaves then curl around the prey, secreting digestive enzymes to break it down.

https://www.mdpi.com/2075-4450/4/3/413

2.3.20 Plants cannot fix nitrogen so atmospheric dinitrogen is unavailable to them unless they form mutualistic associations with nitrogen-fixing bacteria.

Explain why plants cannot fix atmospheric nitrogen on their own.
Describe the mutualistic relationship between Rhizobium bacteria and leguminous plants

https://news.illinois.edu/view/6367/204407

Nitrogen is an essential nutrient for plant growth, but atmospheric dinitrogen (N₂) is unavailable to plants because they cannot fix nitrogen on their own. To overcome this limitation, some plants form mutualistic associations with nitrogen-fixing bacteria. These associations allow plants to access nitrogen in a usable form, providing them with a competitive advantage in ecosystems where nitrogen is a limiting factor.

Mutualistic Associations Between Plants and Nitrogen-Fixing Bacteria

Nitrogen Fixation: Nitrogen-fixing bacteria convert atmospheric nitrogen (N₂) into ammonia (NH₃), which can then be taken up by plants and used to synthesize essential organic compounds such as amino acids and proteins.
- Enzyme: The enzyme nitrogenase, found in nitrogen-fixing bacteria, catalyzes the conversion of N₂ to NH₃.

Types of Nitrogen-Fixing Bacteria:

Free-Living Bacteria: Such as Azotobacter, which fix nitrogen independently in the soil.
Symbiotic Bacteria: Such as Rhizobium and Frankia, which form mutualistic associations with plants.

Plants Forming Mutualistic Associations:

Leguminous Plants: These plants form nodules on their roots where Rhizobium bacteria reside.
- Examples: Peas (Pisum sativum), beans (Phaseolus vulgaris), clover (Trifolium spp.), and soybeans (Glycine max).
- Mechanism:
  - The plant roots secrete flavonoids that attract Rhizobium bacteria.
  - The bacteria infect the root hairs, leading to the formation of root nodules.
  - Within the nodules, Rhizobium bacteria convert N₂ into ammonia, which the plant can use.
Non-Leguminous Plants: These plants form symbiotic relationships with Frankia bacteria.
- Examples: Alder (Alnus spp.) and certain species of actinorhizal plants like sweetfern (Comptonia peregrina) and bayberry (Myrica spp.).
- Mechanism:
  - Similar to leguminous plants, Frankia bacteria form nodules on the roots of these plants and fix atmospheric nitrogen.

2.3.21 Flows in the nitrogen cycle include mineral uptake by producers, photosynthesis, consumption, excretion, death, decomposition and ammonification.

Describe the process of mineral uptake by producers

The nitrogen cycle is a complex biogeochemical cycle that involves various flows of nitrogen through the atmosphere, soil, water, and living organisms. These flows include processes such as mineral uptake by producers, photosynthesis, consumption, excretion, death, decomposition, and ammonification. Understanding these flows and their transformations and transfers is crucial for comprehending how nitrogen moves through ecosystems.

Flows in the Nitrogen Cycle

Mineral Uptake
- Plants absorb inorganic nitrogen compounds (such as nitrates, NO₃⁻, and ammonium, NH₄⁺) from the soil through their roots.
- This uptake is essential for plant growth and the synthesis of proteins, nucleic acids, and other nitrogen-containing compounds.
Photosynthesis:
- Plants convert carbon dioxide (CO₂) and water (H₂O) into glucose (C₆H₁₂O₆) and oxygen (O₂) using sunlight. Although primarily a carbon fixation process, photosynthesis supports nitrogen assimilation by providing the energy and organic molecules necessary for growth.
- This process transforms light energy into chemical energy stored in organic molecules.
Consumption:
- Herbivores consume plants, obtaining the nitrogen stored in plant tissues. Carnivores, in turn, consume herbivores, transferring nitrogen through the food web.
- This flow involves the transfer of nitrogen from one organism to another within the ecosystem.
Excretion:
- Animals excrete nitrogenous waste products (such as urea, uric acid, and ammonia) into the environment.
- Excretion transfers nitrogen from living organisms back into the soil and water.
Death:
- When plants and animals die, their bodies become part of the organic matter in the ecosystem.
- Death transfers nitrogen from living organisms to dead organic matter.
Decomposition:
- Decomposers (bacteria and fungi) break down dead organic matter, converting it into simpler organic compounds and inorganic nutrients.
- Decomposition transforms complex organic nitrogen compounds into simpler forms, such as ammonia.
Ammonification:
- Decomposers convert organic nitrogen in dead organisms and waste products into ammonia (NH₃), which can be further converted to ammonium (NH₄⁺) in the soil.
- Ammonification transforms organic nitrogen into inorganic ammonia.

Transformation Flows:

Photosynthesis: Converts light energy into chemical energy, supporting nitrogen assimilation in plants.
Decomposition: Transforms complex organic nitrogen compounds into simpler forms.
Ammonification: Converts organic nitrogen into inorganic ammonia.

Transfer Flows:

Mineral Uptake: Transfer of inorganic nitrogen from soil to plants.
Consumption: Transfer of nitrogen through the food web from plants to herbivores and then to carnivores.
Excretion: Transfer of nitrogen from animals back into the environment.
Death: Transfer of nitrogen from living organisms to dead organic matter.

Application of skills: Create a systems diagram of the nitrogen cycle.

human activity on Nitrogen cycle

2.3.22 Human activities such as deforestation, agriculture, aquaculture and urbanization change
the nitrogen cycle.

Discuss the impacts of human activity on the nitrogen cycles.

image from www.drmonline.ne

Humans clearly disrupt many, if not all biogeochemical cycles and in the process threaten many ecosystems. In resent years human activities have directly or indirectly affected the biogeochemical cycles that determine climatic conditions of earth. It is imperative to mention that, managing and understanding environmental problems caused by climate change would require an understanding of the biogeochemical cycles. Biogeochemical cycles always involve equilibrium states: a balance in the cycling of the element between spheres. However, overall balance may involve elements distributed on a global scale and that is why a disruption in one cycle causes a disruption in all other cycles. Below is a summary of how human activities have contributed to disruption of biogeochemical cycles. For impacts on specific cycles, the reader should refer to the sites where these cycles are presented.

Burning Fossil Fuels

Combustion of fossil fuels have altered the way in which energy from the Sun interacts with the atmosphere and the planet. Increased CO levels, and the corresponding increase in temperature have led to the reduction of Arctic Sea ice, reducing the amount of reflected sunlight energy
Changes in the atmosphere through pollution have led to increased interception of radiation from the Sun, through changes in reflection by scatter from tiny atmospheric particles

Deforestation:

Timber harvesting interferes with nutrient cycling, especially in tropical rainforests, where soils have low fertility and nutrient cycle between the leaf litter and tree biomass. Rapid decomposition, due to warm conditions and high rainfall, leads to the breakdown of rich leaf litter. Once the trees have been removed, the canopy no longer intercepts rainfall and the soil and leaf letter is washed away.

Aquaculture:

Aquaculture can also affect the nitrogen cycle. Fish farms often use large amounts of fertilizers and antibiotics, which can pollute the surrounding water bodies

Urbanization

Wetlands are drained to allow for expansion of urban areas. Since denitrification takes place in wetland areas denitrification is reduced and less nitrogen enters the atmosphere.

Agriculture:

As a result of extensive cultivation human beings have more than doubled the annual transfer of nitrogen into biologically available forms. Humans have significantly contributed to the transfer of nitrogen gases from Earth to the atmosphere, and from the land to aquatic systems through four main processes:
The application of nitrogen fertilizers to crops has caused increased rates of denitrification and leaching of nitrate into groundwater. The additional nitrogen entering the groundwater system eventually flows into streams, rivers, lakes, and estuaries. In these systems, the added nitrogen can lead to eutrophication.
Increased deposition of nitrogen from atmospheric sources because of fossil fuel combustion and forest burning. Both of these processes release a variety of solid forms of nitrogen through combustion.

Mining of Fossil fuels:

Humans have interfered with the carbon cycle where fossil fuels have been mined from the earth crust. Had fossils not been discovered prior to industrial revolution, they could have remained there until now. Carbon dioxide is number one greenhouse gas contributing to global warming and climate change. Additionally, clearing of vegetation that serve as carbon sinks has increased the concentration of carbon dioxide in the atmosphere.

Livestock ranching:

Livestock release a large amounts of ammonia into the environment from their wastes. This nitrogen enters the soil system and then the hydrologic system through leaching, groundwater flow, and runoff.

2.3.23 The Haber process is an industrial process that produces ammonia from nitrogen and
hydrogen for use as fertilizer.

Describethe Haber process
Outline the advantages and disadvantages of using the Haber process for fertilizer production.

The Haber process, also known as the Haber-Bosch process, is an industrial method for synthesizing ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂) gases. This process is fundamental for producing fertilizers, which significantly enhance agricultural productivity. However, the use of the Haber process also comes with both advantages and disadvantages.

Chemical Reaction:

Equation: N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g)
Conditions: The reaction typically occurs at high temperatures (around 450-500°C) and high pressures (150-200 atmospheres) in the presence of an iron catalyst.

Raw Materials:

Nitrogen (N₂): Sourced from the air, which is composed of approximately 78% nitrogen.
Hydrogen (H₂): Usually derived from natural gas (methane) through a process called steam reforming, where methane reacts with water to produce hydrogen and carbon dioxide (CO₂).
Output: The ammonia produced is used primarily to manufacture fertilizers such as ammonium nitrate (NH₄NO₃) and urea (CO(NH₂)₂), which provide essential nitrogen for plant growth.

https://chemistrytalk.org/haber-process/

2.3.24 Increases in nitrates in the biosphere from human activities have led to the planetary boundary for the nitrogen cycle being crossed, making irreversible changes to Earth systems likely.

Explain the significance of the 'planetary boundary' in the context of the nitrogen cycle.
Discuss two major environmental impacts of crossing the nitrogen cycle planetary boundary.

https://www.researchgate.net/figure/Proposed-new-planetary-boundaries-framework-Updated-version-of-the-planetary-boundaries_fig2_356855403

There is growing evidence that human activities have crossed the planetary boundary for the nitrogen cycle, leading to potentially irreversible changes in Earth's ecosystems. The Stockholm Resilience Centre has highlighted this concern, showing that increased nitrate levels, eutrophication, and decreased biodiversity are key indicators of this boundary being breached. The primary cause of this violation is the global dependence on inorganic fertilizers for crop production, particularly those produced using the Haber-Bosch process.

Increased Nitrate Levels:

The concentration of nitrates in rivers, lakes, and groundwater has been steadily rising.
Widespread use of fertilizers, manure, and other sources of nitrogen pollution contribute to this increase.
Elevated nitrate levels can lead to water pollution, making it unsafe for drinking and harming aquatic life.

Eutrophication:

Eutrophication is the excessive growth of algae and other aquatic plants due to an abundance of nutrients, primarily nitrogen and phosphorus.
This process leads to oxygen depletion, habitat destruction, and fish kills in affected water bodies.
Many rivers, lakes, and coastal areas worldwide have experienced severe eutrophication, resulting in dead zones where aquatic life cannot survive.

Decreased Biodiversity:

Excessive nitrogen inputs disrupt natural ecosystems, leading to declines in biodiversity.
Nitrogen pollution favors certain species over others, causing imbalances in food webs and reducing species diversity.
Loss of biodiversity weakens ecosystem resilience and functionality, affecting services that ecosystems provide to humans.

Causes of Planetary Boundary Violation

Inorganic fertilizers are primarily produced using this process, which synthesizes ammonia from atmospheric nitrogen.
The demand for high crop yields has led to the extensive use of these fertilizers, contributing to nitrogen pollution.
The reliance on inorganic fertilizers has drastically increased the amount of bioavailable nitrogen in the environment, exceeding natural levels.

Impacts of Irreversible Changes

Eutrophication leads to degraded water quality, making it unsafe for human consumption and harmful to aquatic ecosystems.
Contaminated water can cause health problems, particularly in infants and vulnerable populations.

Reduced Food Security:

Excessive nitrogen pollution can harm crops, reducing yields and potentially threatening food security.
Lower crop productivity can affect farmers' livelihoods and global food supply chains.

Harm to Human Health:

High nitrate levels in drinking water pose health risks, including methemoglobinemia (blue baby syndrome) in infants.
Nitrogen compounds can contribute to the formation of fine particulate matter, impacting respiratory health.

2.3.25 Global collaboration is needed to address the uncontrolled use of nitrogen in industrial and
agricultural processes and bring the nitrogen cycle back within planetary boundaries.

Explain why global collaboration is necessary to manage the nitrogen cycle
Discuss the role of international agreements and policies in regulating nitrogen emissions from industrial processes.

The uncontrolled use of nitrogen in industrial and agricultural processes has led to the crossing of the planetary boundary for the nitrogen cycle, resulting in significant environmental and health challenges. Addressing this issue requires global collaboration and the implementation of comprehensive measures to bring the nitrogen cycle back within safe limits.

Need for Global Collaboration

Shared Responsibility:
- Nitrogen pollution affects ecosystems and human health worldwide, making it a global issue that requires coordinated efforts.
- The nitrogen cycle is interconnected with other biogeochemical cycles and Earth systems, necessitating international cooperation to address the complex challenges.
International Agreements and Policies:
- Existing frameworks, such as the Paris Agreement and the Sustainable Development Goals (SDGs), provide platforms for collaboration on nitrogen management.
- Developing and enforcing international regulations on nitrogen use can help standardize practices and reduce global nitrogen pollution.

Measures to Restore Planetary Boundaries

Efficient Fertilizer Use:
- Implementing precision farming and optimizing fertilizer application can reduce runoff and minimize nitrogen pollution.
- Providing farmers with knowledge and tools to use fertilizers more efficiently.
Promoting Sustainable Agriculture:
- Growing cover crops can improve soil health and reduce the need for synthetic fertilizers.
- Rotating crops helps maintain soil fertility and reduce pest and disease pressures.
Reducing Nitrogen Emissions:
- Reducing nitrogen emissions from power plants and other industrial sources can help mitigate overall nitrogen input to the environment.
- Implementing stricter regulations on nitrogen emissions and enforcing compliance.
Promoting Alternative Nitrogen Sources:
- Encouraging the use of legumes and other nitrogen-fixing plants can naturally enhance soil nitrogen levels.
- Investing in the development of alternative nitrogen sources and sustainable agricultural practices.

Key Terms

biogeochemical cycle
carbon cycle
carbon stores
carbons sinks
carbon sources
residence time

HL ONLY
lithosphere
nitrogen cycle
methanogenesis
nitrates
nitrites
denitrification
anaerobic conditions
eutrophication
planetary boundaries
global collaboration
Haber Process
nitrogen-fixing bacteria.
legumes
nitrogen fixation
ammonification
decomposition
leaching

regenerative agricultural
fossil fuels
limestone
fossilization

carbon sequestration
carbon capture
artificial sequestration
sustainable agriculture

ocean acidification
photosynthesis
cellular respiration
soil erosion
deforestation

biomass
reforestation
inorganic fertilizers
ocean acidification

Classroom Material

Subtopic 2.3 Biogeochemical Cycle Workbook.docx
File Size:	1129 kb
File Type:	docx

Download File

Subtopic 2.3 Biogeochemical Cycles.pptx
File Size:	13211 kb
File Type:	pptx

Download File

Activity: Create a systems diagram of the carbon cycle.
Activity: Field trip to local forests, wetlands, or farms to study carbon storage and sequestration practices firsthand
Activity: Students design an experiment to measure soil carbon changes over time with different agricultural practices
Activity: Provide students with real-world data sets on carbon emissions, forest cover, or ocean pH levels and guide them through the process of data analysis and interpretation.
Activity: Students conduct experiments to simulate acidification and measure its impact on calcium carbonate formation.

Human Impact of Biogeochemcial Cycles - Global Change article
Deforestation and the Carbon Cycle - EarthLabs

Correct use of terminology is a key skill in ESS. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.

Useful Links

Carbon Cycle Game - Windows 2 Universe
Carbon Cycle - BBC Bitesize
Carbon Cycle Online Modeling - Annenberg Learner
Water Cycle Interactive - EPA
Water Cycle Game - Southeast Water
Nitrogen Cycle Interactive - Classzone
Nitrogen Cycle Animation - Vermont County Extension Service
The Nitrogen Cycle - Nature

In The News
Why Restoring Nature Could Be the Key to Fighting Climate Change - Time, 15 Oct 2015
As large animals disappear, the loss of their poop hurts the planet - Washington Post - 25 Oct 2015

TOK

"To what extent does scientific knowledge about biogeochemical cycles impose an ethical responsibility on individuals and societies to change their environmental practices?"

International-mindedness

"Recognizing the global nature of biogeochemical cycles underscores our interconnectedness and shared responsibility to manage Earth's resources sustainably, fostering a collective effort to mitigate environmental impacts and promote ecological balance across nations and cultures."

Video Clips

Earth's energy budget is a metaphor for the delicate equilibrium between energy received from the Sun versus energy radiated back out in to space. Research into precise details of Earth's energy budget is vital for understanding how the planet's climate may be changing, as well as variabilities

Hank introduces us to biogeochemical cycles by describing his two favorites: carbon and water. The hydrologic cycle describes how water moves on, above, and below the surface of the Earth, driven by energy supplied by the sun and wind. The carbon cycle does the same... for carbon!

It is important to understand the carbon cycle in order to understand climate change

Hank describes the desperate need many organisms have for nutrients (specifically nitrogen and phosphorus) and how they go about getting them via the nitrogen and phosphorus cycles.

Nitrogen Cycle