Section 4 Lecture 4 (Biogeochemical Cycles) PDF

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Download Section 4 Lecture 4 (Biogeochemical Cycles) PDF

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Key terms: - Biogeochemical cycles: a pathway by which a chemical substance moves through both the biotic and abiotic components of earth. Flux of essential nutrients through the earth system: nutrient cycle. - Biological magnification: contaminants taken up in low levels by primary producers. Concentration increases at each trophic level. Concentrations are high at the top. - Nutrient cycles: movement and exchange of organic and inorganic matter back into the production of living matter. - Photosynthesis: Process by which plants and some use energy from sunlight to produce glucose from carbon dioxide and water. Focus Questions What are the most important BGCs in the earth system? ● Carbon cycle is important because it is the basic building block of organic compounds. Photosynthesis is the primary flux from the atmosphere and many pathways to the atmosphere. ● Nitrogen cycle is important because atmospheric N2 is inaccessible to most organisms and the Nitrogen cycle provides nitrogen in the form of Nitrate or Ammonium ions that plants are able to take up. Animals require N in an organic compound and this makes the Nitrogen cycle essential to life on earth. ● Oxygen cycle How does material move through the earth system? What are stocks and sinks? ● Flux: the rate of transfer - the amount per unit of time - of a chemical that enters or leaves a storage compartment. BGC involve flux of material between storage compartments (sources to sinks). ● Open and Closed Systems: An open system exchanges energy and materials with the outside environment. A closed system is a region that is isolated from its surroundings. ● Reservoirs: In terms of BGC's, places where the element is accumulated or held for a long period of time. ● Sinks: material, such as a chemical. The donating compartment is called a source, and there generally is a flux or rate of transfer between the source and sink. How are humans affect biogeochemical cycles? Are these effects reversible? ● Carbon cycle: Humans are shifting carbon from the lithosphere to the atmosphere. By mining fossil fuel deposits, we are removing carbon from an underground reservoir with a residence time of millions of years. By combusting these fuels, we release CO2 and greatly increase the flux of Carbon from ground to air. Also, deforestation removes carbon from pool of vegetation and releases it into air. ● Nitrogen cycle: Haber-Bosch process of producing ammonia has enabled people to overcome the limits on productivity due to nitrogen scarcity in nature constraints.This process is fixing at least as much nitrogen as is being fixed naturally; doubling the rate of nitrogen fixation on Earth. ● Phosphorus cycle: We mine rocks containing phosphorus to extract this nutrient for inorganic fertilizers. Wastewater discharge rich in phosphates. Runoff into waterways can boost algal growth, causing eutrophication altering ecosystem....