Biogeochemical Cycles PDF

BIOGEOCHEMICAL CYCLES GROUP 3 What are Biogeochemical cycles? Nutrient cycles, also known as biogeochemical cycles, involve the movement of chemical substances between the biosphere (living organisms), geosphere (earth), hydrosphere (water), and atmosphere (air). They ensure that essential...

BIOGEOCHEMICAL CYCLES GROUP 3 What are Biogeochemical cycles? Nutrient cycles, also known as biogeochemical cycles, involve the movement of chemical substances between the biosphere (living organisms), geosphere (earth), hydrosphere (water), and atmosphere (air). They ensure that essential elements like carbon, nitrogen, oxygen, phosphorus, and water are continuously exchanged between organisms and the environment, maintaining balance in ecosystems.  Nutrients that are required by organisms, primarily autotrophs, may be classified into: 1. MACRONUTRIENTS- are required in relatively large amounts and they include: Carbon, Hydrogen, Oxygen, Nitrogen, Potassium, Calcium, Magnesium and Sulfur and Phosphorus 2. MICRONUTRIENTS - are required in small quantities, among the are: Iron, Manganese Copper, Zinc, Boron, Sodium and so on These nutrients have to cycle in ecosystems because the continued functioning and maintenance of an ecosystem depends on the supply and circulation of these nutrients  Biogeochemical cycles have two basic types: 1. Gaseous Nutrient Cycle- the main source of nutrients are the atmosphere and the ocean ➤ The gases which are most important for life are nitrogen, oxygen and carbon dioxide ➤ These three gases in stable quantities of 78%, 21% and 0.03%, respectively Example: Nitrogen, Oxygen and Carbon Cycles 2. Sedimentary Nutrient Cycle- the main sources are soil, rocks and minerals ➤ The mineral elements that living organisms require come initially from inorganic source ➤ Mineral salts come directly from the Earth's crust through weathering Example: Sulfur Cycle, Phosphorus Cycle BIOGEOCHEMICAL CYCLES  5 BIOGEOCHEMICAL CYCLES WATER CYCLE PHOSPHORUS CARBON OXYGEN NITROGEN WATER CYCLE CARBON-OXYGEN CYCLE  RELATIONSHIP BETWEEN CARBON AND OXYGEN CYCLE The carbon cycle is fully coupled to the oxygen cycle. Each year, photosynthesis fixes carbon dioxide and releases 100,000 megatons of oxygen to the atmosphere. Respiration by animals and living organisms consumes about the same amount of oxygen and produces carbon dioxide in return. Oxygen and carbon dioxide are thus coupled in two linked cycles. What is the Carbon-Oxygen cycle? The carbon-oxygen cycle refers to the interconnected processes through which carbon and oxygen are exchanged among the atmosphere, living organisms, oceans, and the Earth’s crust. In this cycle, plants and other chlorophyll-bearing organisms take in carbon dioxide from the environment and use this gas during photosynthetic organisms such as algae and certain protists release oxygen, a by-product of photosynthesis, into the atmosphere and this is taken in by animals and other aerobic organisms (including microorganisms and decomposers). Terrestrial organisms obtain oxygen directly from the atmosphere, while aquatic organisms obtain oxygen dissolved in water. Why is it important? The carbon and oxygen cycles are crucial for regulating Earth's climate, supporting life, and maintaining ecosystem health. The carbon cycle balances CO₂ levels, enriches soil fertility, and helps address climate change, while the oxygen cycle maintains atmospheric oxygen, supports respiration, enables photosynthesis, and sustains healthy ecosystems. Together, they ensure the recycling of essential nutrients and the stability of environmental conditions. THE MAIN EFFECT OF EXCESSIVE CARBON: GLOBAL WARMING 1.Temperature rise 2.Ecosystem Disruption 3.Human Health (explanation will be added on the script)  The Stages of the Carbon- Oxygen Cycle  Photosynthesis This is the process by which green plants and certain other organisms transform light energy into chemical energy. During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds.  Respiration The process of respiration begins when organisms, including plants, animals, and microorganisms, take in oxygen (O₂) from their surroundings. This oxygen is crucial for the breakdown of glucose, a type of sugar that serves as a primary source of energy. Inside the cells, glucose undergoes a series of biochemical reactions to produce energy. As glucose is broken down to release energy, CO₂ is produced and expelled from the cells. This carbon dioxide then re- enters the atmosphere or, in aquatic environments, the water. In the carbon cycle, CO₂ is utilized by plants during photosynthesis to produce glucose and release oxygen, thus maintaining the cycle.  Respiration Respiration also influences the oxygen cycle. The oxygen consumed during respiration is replenished by plants through photosynthesis, where they release oxygen as a byproduct. This ongoing exchange helps keep atmospheric oxygen levels balanced and available for respiration and other vital processes.  Decomposition This is the process that when organisms die, decomposers like bacteria and fungi break them down, releasing carbon into the soil and atmosphere as CO₂ and other organic compounds. The remains of plants and animals accumulate in the ground for over millions of years, and are subjected to physical prosses that transform them into fossil fuels, such as coal and petroleum.  Combustion This is the process in the carbon-oxygen cycle that involves the burning of organic materials to release energy. During combustion, carbon (C) in the organic material is converted into carbon dioxide (CO₂) and water (H₂O). Carbon dioxide is released into the atmosphere, while water vapor can condense and fall as precipitation or remain in the atmosphere. Impact of Combustion Human activities, such as the burning of fossil fuels for energy (coal, oil, and natural gas) and deforestation, significantly impact the carbon-oxygen cycle. When fossil fuels are burned, they release large amounts of CO₂ into the atmosphere, which contributes to climate change. Additionally, deforestation reduces the number of trees available to absorb CO₂, exacerbating the problem.  Carbon Sequestration This is the process of capturing and storing carbon dioxide (CO₂) from the atmosphere or other sources to prevent it from contributing to climate change. Trees and plants, for example, are integral to natural carbon sequestration. During photosynthesis, they absorb CO₂ from the air and convert it into organic matter. This carbon is then stored in their biomass, including trunks, branches, and leaves. Additionally, carbon is sequestered in the soil through plant root systems, where it remains stored for long periods.  Conclusion This is the process of capturing and storing carbon dioxide (CO₂) from the atmosphere or other sources to prevent it from contributing to climate change. Trees and plants, for example, are integral to natural carbon sequestration. During photosynthesis, they absorb CO₂ from the air and convert it into organic matter. This carbon is then stored in their biomass, including trunks, branches, and leaves. Additionally, carbon is sequestered in the soil through plant root systems, where it remains stored for long periods. * The element carbon is stored in various forms of organis compounds such as carbohydrates, fats, proteins, and nucleic acids.It is also retained in the bodies of consumers until they die.Carbon and waste products of dead organisms accumulate in the soil. After hundreds to thousands of years, the organic compounds form part of fossls and fossil fuels. Ocean uptake may also bring about release of carbon dioxide. * Organic carbon found in carbohydrates produced in photosynth is utilized during cellular respiration.It is passed from producers to consumers, for example, from trees to sheep.Carbon stored in the form of compounds of carbohydrates, fats, and the like is retained in the bodies of the consumers until they die.It is finally released as carbon dioxide when the remains of the consumers decompose. The remains of plants and animals accumulate in the ground for over millions of years, and are subjected to physical prosses that transform them into fossil fuels, such as coal and petroleum. WATER CYCLE What is the Water cycle? The water cycle shows the continuous movement of water within the Earth and atmosphere. It is a complex system that includes many different processes. Liquid water evaporates into water vapor, condenses to form clouds, and precipitates back to earth in the form of rain and snow. Why are water processes important? The water cycle is an extremely important process because it enables the availability of water for all living organisms and regulates weather patterns on our planet. If water didn’t naturally recycle itself, we would run out of clean water, which is essential to life. The Stages of the Water Cycle Evaporation Evaporation takes place when solar energy heats bodies of water (oceans, lakes, rivers), causing the liquid water to turn into vapor (gas) and rise into the atmosphere. Oceans are the primary source of evaporation because they cover about 71% of the Earth’s surface.  Transpiration Transpiration is the process where plants absorb water through their roots and release water vapor into the air through tiny openings in their leaves, contributing to the overall moisture content of the atmosphere.  Condensation Condensation occurs when warm water vapor rises into the atmosphere and cools down and condenses to form tiny droplets of water or ice, leading to the formation of clouds. This phase change from gas to liquid is crucial in driving weather patterns.  Precipitation Precipitation takes place when water droplets in clouds coalesce, growing large enough to overcome air resistance and fall back to the Earth in the form of rain, snow, sleet, or hail. Precipitation replenishes freshwater sources and is essential for ecosystems.  Runoff Runoff refers to the movement of water, usually from precipitation, across the Earth's surface. Precipitation that doesn’t infiltrate the ground flows across the land’s surface (runoff), collecting in rivers, lakes, and eventually the ocean. This runoff can erode land and shape landscapes over time.  Subsurface outflow Subsurface flow refers to the movement of water beneath the Earth's surface through soil and rock layers. After water infiltrates the ground through precipitation, it travels through soil and rock layers in a process known as percolation. This subsurface water either slowly flows back to rivers, lakes, or oceans, or it is stored as groundwater in aquifers. Infiltration Infiltration is the process by which water on the Earth's surface, typically from precipitation, snowmelt, or irrigation, enters the soil and moves downward into the ground.  Conclusion The water cycle is a continuous and dynamic system that drives the movement of water throughout the Earth's atmosphere, surface, and subsurface. It involves key processes such as evaporation, Transpiration, condensation, precipitation, infiltration, runoff, and subsurface outflow, which work together to distribute water across the planet. This cycle supports life by providing freshwater, regulating climate, and sustaining ecosystems. PHOSPHORUS CYCLE The phosphorus cycle is the biogeochemical process that describes the movement of phosphorus through the lithosphere (Earth's crust), hydrosphere (water bodies), and biosphere (living organisms). Unlike other cycles (like carbon or nitrogen), phosphorus does not have a gaseous phase at Earth's surface, meaning it doesn't enter the atmosphere in significant amounts.  The Stages of the Phosphorus Cycle  Phosphate rock formation Phosphate rocks, also referred to as phosphorites, are sedimentary deposits with high phosphorus (P) concentrations. These rocks are one of the primary ore sources for phosphate, which in turn is a critical and non-renewable element for fertilizer production, upon which global fertility depends. The startling limitation of phosphate rock reserves has led to a renewed intensity of research in mitigating P loss from landscapes, recycling P from waste streams, and exploring new P ore potentials.  Weathering Weathering is the processes, such as rain and erosion, break down rocks and release phosphorus into the soil and water. Phosphorus is found in the rocks in abundance. That is why the phosphorus cycle starts in the earth’s crust. The phosphate salts are broken down from the rocks. These salts are washed away into the ground where they mix in the soil.  Plants Plants take up inorganic phosphate from the soil. The plants may then be consumed by animals. Once in the plant or animal, the phosphate is incorporated into organic molecules such as DNA. When the plant or animal dies, it decays, and the organic phosphate is returned to the soil.  Animals The animals absorb phosphorus from the plants or by consuming plant-eating animals. The rate of the phosphorus cycle is faster in plants and animals when compared to rocks.  Soils Soil contains minerals that are rich in phosphorus. These minerals are classified into primary and secondary minerals. Minerals break down over time (a process referred to as weathering) and release phosphorus in the soil solution for plant uptake.  Sedimentation The sedimentation of phosphorus occurs when organic phosphorus is released during either, excretion or decomposition, if this organic phosphorus is not taken up within the water column it will settle to the bottom of the lake.  Fertilizer runoff fertilizers are used, they potentially enter the soil and water through run-off, as shown in the image below. Phosphates are transferred to rivers, lakes, and the ocean from agricultural crops, residential lawns, or any other places that use these fertilizers during periods through run-off.  Conclusion The phosphorus cycle is a crucial biogeochemical process that sustains life on Earth. While phosphorus is a limiting nutrient in many ecosystems, human activities have disrupted its natural balance. Understanding the phosphorus cycle and its human impacts is essential for managing environmental resources and promoting sustainable practices. NITROGEN CYCLE What is the Nitrogen cycle? The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification.  Today, the Earth’s atmosphere is about 78% nitrogen, about 21% oxygen, and about 1% other gases. This is an ideal balance because too much oxygen can actually be toxic to cells. In addition, oxygen is flammable. Nitrogen, on the other hand, is inert and harmless in its gaseous form. However, nitrogen gas is not accessible to plants and animals for use in their cells. (explanation will be added on the script) The Stages of the Nitrogen Cycle Nitrogen Fixation This is the process of converting nitrogen gas from the atmosphere into a form that plants can use. For nitrogen to be available to make proteins, DNA, and other biologically important compounds, it must first be converted into a different chemical form (Ammonia). The process of converting N2 into biologically available nitrogen is called nitrogen fixation. N2 gas is a very stable compound due to the strength of the triple bond between the nitrogen atoms, and it requires a large amount of energy to break this bond.  Nitrification This is the process that converts ammonia to nitrite and then to nitrate and is another important step in the global nitrogen cycle. Most nitrification occurs aerobically and is carried out exclusively by prokaryotes. (explanation will be added on the script)  Two Steps of Nitrification 1st STEP: Ammonia to 2nd STEP: Nitrite to Nitrite Nitrate The first step is carried out by ammonia- The second step is performed by nitrite- oxidizing bacteria (AOB) or archaea. oxidizing bacteria. These bacteria convert These microorganisms convert ammonia nitrite (NO₂⁻) into nitrate (NO₃⁻). This step is (NH₃) into nitrite (NO₂⁻). This step is known as nitrite oxidation. known as ammonia oxidation. (explanation will be added on the script)  Assimilation This is the process by which plants and animals incorporate the NO3- and ammonia formed through nitrogen fixation and nitrification. Plants take up these forms of nitrogen through their roots, and incorporate them into plant proteins and nucleic acids. Animals are then able to utilize nitrogen from the plant tissues.  Ammonification When an organism excretes waste or dies, the nitrogen in its tissues is in the form of organic nitrogen (e.g. amino acids, DNA). Various fungi and prokaryotes then decompose the tissue and release inorganic nitrogen back into the ecosystem as ammonia in the process known as ammonification. The ammonia then becomes available for uptake by plants and other microorganisms for growth.  Denitrification This is the process that converts nitrate to nitrogen gas, thus removing bioavailable nitrogen and returning it to the atmosphere. Dinitrogen gas (N2) is the ultimate end product of denitrification, but other intermediate gaseous forms of nitrogen exist. Some of these gases, such as nitrous oxide (N2O), are considered greenhouse gasses, reacting with ozone and contributing to air pollution.  Conclusion The nitrogen cycle is a crucial ecological process that ensures the continuous availability of nitrogen, an essential nutrient for all living organisms. It involves the transformation of nitrogen through various forms and processes, including nitrogen fixation, nitrification, assimilation, ammonification, and denitrification. Each step is carried out by different microorganisms and environmental factors, making the cycle a dynamic and interconnected system. By converting atmospheric nitrogen into forms usable by plants and then recycling it back into the atmosphere, the nitrogen cycle supports ecosystem productivity and maintains soil health. Understanding and protecting this cycle is vital for sustaining agricultural productivity and ecosystem balance. SULFUR CYCLE  What is the Sulfur Cycle? A biogeochemical cycle that describes the movement of sulfur through the lithosphere, hydrosphere, atmosphere, and biosphere. Important for living organisms, as sulfur is a key component of proteins and vitamins. The Processes in the Sulfur Cycle Weathering of Rocks: Releases sulfur into the soil. Volcanic Activity: Releases sulfur dioxide (SO₂) into the atmosphere. Sulfur Assimilation: Plants absorb sulfur in the form of sulfate (SO₄²⁻). Decomposition: Bacteria decompose dead organisms, returning sulfur to the soil and atmosphere. Acid Rain: Sulfur dioxide (SO₂) combines with water vapor to form sulfuric acid (H₂SO₄), leading to acid rain. Sulfur's Atmospheric Role Sulfur dioxide (SO₂) released by burning fossil fuels, volcanic eruptions, and decay. Sulfuric acid (H₂SO₄) formation leads to acid rain, affecting ecosystems and buildings. Interaction with clouds can impact weather patterns and climate. Oceanic Sulfur Marine organisms take up sulfate ions (SO₄²⁻) and use them in biological processes. Dimethyl sulfide (DMS) released by phytoplankton contributes to cloud formation. Sulfates in ocean sediments return to the lithosphere over time. How Humans Affect the Sulfur Cycle Burning of fossil fuels (coal and oil) increases sulfur dioxide (SO₂) in the atmosphere. Industrial processes like smelting release sulfur compounds. Acid rain from SO₂ leads to environmental damage, affecting soil pH, plant life, and aquatic systems.  Consequences of Altered Sulfur Cycle Acid Rain: Lowers pH of lakes, streams, and soil, impacting aquatic and terrestrial ecosystems. Climate Impact: Sulfur aerosols in the atmosphere can cool the Earth by reflecting sunlight. Biodiversity Loss: Acid rain and pollution can harm sensitive plant and animal species. Solutions and Mitigation Efforts Reducing Emissions: Clean energy alternatives to fossil fuels. Scrubbers in Factories: To reduce sulfur dioxide (SO₂) emissions. Legislation: Policies like the Clean Air Act aimed at controlling sulfur emissions. Ecosystem Restoration: Liming acidic soils and water bodies to neutralize acid rain effects. Summary of the Sulfur Cycle The sulfur cycle is a crucial part of Earth’s systems, linking atmosphere, land, and ocean. Human activities have intensified sulfur emissions, leading to environmental challenges. Sustainable practices and mitigation efforts are necessary to preserve ecological balance.