Biogeochemical Cycles Explained
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The document discusses biogeochemical cycles, which describe the movement of chemical elements through the biosphere, lithosphere, atmosphere, and hydrosphere. It specifically examines the carbon, water, nitrogen, phosphorus, oxygen, and sulfur cycles. Each cycle involves the movement of an element through various pools and fluxes between the biotic and abiotic components of Earth, driven by both physical and biological processes. Human activities have significantly impacted these natural cycles through activities like burning fossil fuels, agriculture, deforestation, and industrialization. Maintaining the natural biogeochemical cycles is essential for sustaining life on Earth.
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Biogeochemical Cycles Explained
- 1. Biogeochemical Cycles Course : B.Sc. Microbiology/ Bio-Technology/ Bio-Chemistry Sem I Sub: Environmental Science Unit 4
- 2. What are biogeochemical cycles? • Earth system has four parts – Atmosphere – Hydrosphere – Lithosphere – Biosphere • Biogeochemical cycles: The chemical interactions (cycles) that exist between the atmosphere, hydrosphere, lithosphere, and biosphere. • Abiotic (physio-chemical) and biotic processes drive these cycles • Focus on carbon and water cycles (but could include all necessary elements for life). N - cycle weakly touched on! 1
- 3. Biogeochemical Cycle • Bio- life • Geo-earth • Chemical- elements • A biogeochemical cycle or substance turnover or cycling of substances is a pathway by which a chemical substance moves through both biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. A cycle is a series of change which comes back to the starting point and which can be repeated.
- 4. What is common amongst them? • Each compound (water, carbon, nitrogen) typically exists in all four parts of the Earth System • There are – ‘Pools’ – Fluxes in and out of pools – Chemical or biochemical transformations • Transformations – are important – can lead to positive & negative consequences
- 5. What Sustains Life on Earth? • Solar energy, the cycling of matter, and gravity sustain the earth’s life. 2
- 6. Two Secrets of Survival: Energy Flow and Matter Recycle • An ecosystem survives by a combination of energy flow and matter recycling. Figure 3-14Figure 3-14 3
- 7. MATTER CYCLING IN ECOSYSTEMS • Nutrient Cycles: Global Recycling – Global Cycles recycle nutrients through the earth’s air, land, water, and living organisms. – Nutrients are the elements and compounds that organisms need to live, grow, and reproduce. – Biogeochemical cycles move these substances through air, water, soil, rock and living organisms.
- 8. Water’ Unique Properties • There are strong forces of attraction between molecules of water. • Water exists as a liquid over a wide temperature range. • Liquid water changes temperature slowly. • It takes a large amount of energy for water to evaporate. • Liquid water can dissolve a variety of compounds. • Water expands when it freezes.
- 9. PrecipitationPrecipitation Transpiration Condensation Evaporation Ocean storage Transpiration from plants Precipitation to land Groundwater movement (slow) Evaporation from land Evaporation from ocean Precipitation to ocean Infiltration and Percolation Rain clouds Runoff Surface runoff (rapid) Surface runoff (rapid) Water Cycle 4
- 10. • The Water Cycle (also known as the hydrologic cycle) is the journey water takes as it circulates from the land to the sky and back again. The Sun's heat provides energy to evaporate water from the Earth's surface (oceans, lakes, etc.). Plants also lose water to the air (this is called transpiration). The water vapor eventually condenses, forming tiny droplets in clouds. When the clouds meet cool air over land, precipitation (rain, sleet, or snow) is triggered, and water returns to the land (or sea). Some of the precipitation soaks into the ground. Some of the underground water is trapped between rock or clay layers; this is called groundwater. But most of the water flows downhill as runoff (above ground or underground), eventually returning to the seas as slightly salty water.
- 11. The Water Cycle (also known as the hydrologic cycle) 5
- 12. Water Cycle • involves the processes of photosynthesis, transpiration, evaporation and condensation, respiration, and excretion
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- 14. Effects of Human Activities on Water Cycle • We alter the water cycle by: – Withdrawing large amounts of freshwater. – Clearing vegetation and eroding soils. – Polluting surface and underground water. – Contributing to climate change.
- 15. The Carbon Cycle All living things are made of carbon. Carbon is also a part of the ocean, air, and even rocks. Because the Earth is a dynamic place, carbon does not stay still 7
- 16. • In the atmosphere, carbon is attached to some oxygen in a gas called carbon dioxide. • Plants use carbon dioxide and sunlight to make their own food and grow. The carbon becomes part of the plant. Plants that die and are buried may turn into fossil fuels made of carbon like coal and oil over millions of years. When humans burn fossil fuels, most of the carbon quickly enters the atmosphere as carbon dioxide.
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- 18. Effects of Human Activities on Carbon Cycle • We alter the carbon cycle by adding excess CO2 to the atmosphere through: – Burning fossil fuels. – Clearing vegetation faster than it is replaced. 9
- 19. Carbon-Oxygen Cycle • Involves the processes of respiration and photosynthesis. • In respiration, oxygen and glucose are combined releasing energy and producing water and carbon dioxide. • In photosynthesis water and carbon dioxide along with the energy from the sun are combined to produce glucose (containing energy) and oxygen. • Each process compliments the other and the ecosystem maintains its balanced communities.
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- 22. • The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. • The majority of Earth's atmosphere (78%) is nitrogen, making it the largest pool of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. • Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle.
- 23. Nitrogen Cycle • Nitrates (used by plants) • Build plant proteins • Eaten by animals • made into animal proteins • Plants and animals die • bacteria decay • Ammonia (NH3) • Nitrifying Bacteria • Nitrates (used by plants)
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- 27. Effects of Human Activities on the Nitrogen Cycle • We alter the nitrogen cycle by: – Adding gases that contribute to acid rain. – Adding nitrous oxide to the atmosphere through farming practices which can warm the atmosphere and deplete ozone. – Contaminating ground water from nitrate ions in inorganic fertilizers. – Releasing nitrogen into the troposphere through deforestation.
- 28. Effects of Human Activities on the Nitrogen Cycle • Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined. 15
- 29. The biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus-based compounds are usually solids at the typical ranges of temperature and pressure found on Earth.
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- 31. Phosphorus cycle • Phosphates move quickly through plants and animals; however, the processes that move them through the soil or ocean are very slow, making the phosphorus cycle overall one of the slowest biogeochemical cycles. • Initially, phosphate weathers from rocks and minerals, the most common mineral being apatite. Overall small losses occur in terrestrial environments by leaching and erosion, through the action of rain. In soil, phosphate is absorbed on iron oxides, aluminium hydroxides, clay surfaces, and organic matter particles, and becomes incorporated (immobilized or fixed). Plants and fungi can also be active in making P soluble. • Unlike other cycles, P cannot be found in the air as a gas; it only occurs under highly reducing conditions as the gas phosphine PH3.
- 32. Dissolved in Ocean Water Marine Sediments Rocks uplifting over geologic time settling out weatheringsedimentation Land Food Webs Dissolved in Soil Water, Lakes, Rivers death, decomposition uptake by autotrophs agriculture leaching, runoff uptake by autotrophs excretion death, decomposition mining Fertilizer weathering Guano Marine Food Webs 17
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- 35. Effects of Human Activities on the Phosphorous Cycle • We remove large amounts of phosphate from the earth to make fertilizer. • We reduce phosphorous in tropical soils by clearing forests. • We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers.
- 36. What Sustains Life on Earth? • Solar energy, the cycling of matter, and gravity sustain the earth’s life.
- 37. Oxygen cycle 19
- 38. Oxygen cycle • All organisms living an animals breathe in oxygen. Oxygen constitutes about 20% of the atmosphere. It is essential for respiration. It produces energy in living beings by the oxidation of foods. During this process, CO2 is released which is used by the plants in making food during photosynthesis. During the process of photosynthesis, oxygen gas is released back into the atmosphere. Thus, this cycle is completed. 20
- 39. Oxygen cycle 21
- 40. Oxygen cycle • Oxygen cycle, circulation of oxygen in various forms through nature. Free in the air and dissolved in water, oxygen is second only to nitrogen in abundance among uncombined elements in the atmosphere. Plants and animals use oxygen to respire and return it to the air and water as carbon dioxide (CO2). CO2 is then taken up by algae and terrestrial green plants and converted into carbohydrates during the process of photosynthesis, oxygen being a by-product. The waters of the world are the main oxygen generators of the biosphere; their algae are estimated to replace about 90 percent of all oxygen used. Oxygen is involved to some degree in all the other biogeochemical cycles. For example, over time, detritus from living organisms transfers oxygen-containing compounds such as calcium carbonates into the lithosphere.
- 41. Sulphur Cycle Hydrogen sulfide Sulfur Sulfate salts Decaying matter Animals Plants Ocean Industries Volcano Hydrogen sulfide Oxygen Dimethyl sulfide Ammonium sulfate Ammonia Acidic fog and precipitationSulfuric acid WaterSulfur trioxide Sulfur dioxide Metallic sulfide deposits 22
- 42. Effects of Human Activities on the Sulfur Cycle • We add sulfur dioxide to the atmosphere by: – Burning coal and oil – Refining sulfur containing petroleum. – Convert sulfur-containing metallic ores into free metals such as copper, lead, and zinc releasing sulfur dioxide into the environment.
- 43. What do you think? • Does life on earth control earth’s life- sustaining processes or does life merely influence these life-sustaining process?
- 46. Books: 1.Environmental studies by R.Rajagopalan 2.Environmental Science by Richard T Wright & Bernard J Nebel References
Notes de l'éditeur
- Figure 3.26 Natural capital: simplified model of the hydrologic cycle.
- Figure 3.27 Natural capital: simplified model of the global carbon cycle. Carbon moves through both marine ecosystems (left side) and terrestrial ecosystems (right side). Carbon reservoirs are shown as boxes; processes that change one form of carbon to another are shown in unboxed print. QUESTION: What are three ways in which your lifestyle directly or indirectly affects the carbon cycle? (From Cecie Starr, Biology: Concepts and Applications, 4th ed., Pacific Grove, Calif.: Brooks/Cole, © 2000)
- Figure 3.31 Natural capital: simplified model of the phosphorus cycle. Phosphorus reservoirs are shown as boxes; processes that change one form of phosphorus to another are shown in unboxed print. QUESTION: What are three ways in which your lifestyle directly or indirectly affects the phosphorus cycle? (From Cecie Starr and Ralph Taggart, Biology: The Unity and Diversity of Life, 9th ed., Belmont, Calif.: Wadsworth © 2001)
- Figure 3.32 Natural capital: simplified model of the sulfur cycle. The movement of sulfur compounds in living organisms is shown in green, blue in aquatic systems, and orange in the atmosphere. QUESTION: What are three ways in which your lifestyle directly or indirectly affects the sulfur cycle?