CSU2057 Environment Science Lecture 4 PDF

CSU2057 –Environment Science Lecture 4 Topics to be covered today Phosphorus Cycle Key points  Phosphorus is an essential nutrient found in the macromolecules of humans and other organisms, including DNA  The phosphorus cycle is slow. Most phosphorus in nature exists in the form of pho...

CSU2057 –Environment Science Lecture 4 Topics to be covered today Phosphorus Cycle Key points  Phosphorus is an essential nutrient found in the macromolecules of humans and other organisms, including DNA  The phosphorus cycle is slow. Most phosphorus in nature exists in the form of phosphate ion.  Phosphorus is often the limiting nutrient, or nutrient that is most scarce and thus limits growth, in aquatic ecosystems.  When nitrogen and phosphorus from fertilizer are carried in runoff to lakes and oceans, they can cause eutrophication, the overgrowth of algae. The algae may deplete oxygen from the water and create a dead zone. Introduction  Is phosphorus important?  That depends—do you like having DNA, cell membranes, or bones in you body?  Hint: The answer is probably yes!  Phosphorus is an essential nutrient for living organisms. It’s a key part of nucleic acids, like DNA and of the phospholipids that form our cell membranes. As calcium phosphate, it also makes up the supportive components of our bones.  In nature, phosphorus is often the limiting nutrient—in other words, the nutrient that’s in shortest supply and puts a limit on growth— and this is particularly true for aquatic, freshwater ecosystems. Natural cycling of phosphorus  The phosphorus cycle is slow compared to other biogeochemical cycles such as the water, carbon, and nitrogen cycles  In nature, phosphorus is found mostly in the form of phosphate ions.  Phosphate compounds are found in sedimentary rocks, and as the rocks weather—wear down over long time periods—the phosphorus they contain slowly leaches into surface water and soils.  Volcanic ash, aerosols, and mineral dust can also be significant phosphate sources, though phosphorus has no real gas phase, unlike other elements such as carbon, nitrogen, and sulfur.  Phosphate compounds in the soil can be taken up by plants and, from there, transferred to animals that eat the plants.  When plants and animals excrete wastes or die, phosphates may be taken up by detritivores or returned to the soil.  Phosphorus-containing compounds may also be carried in surface runoff to rivers, lakes, and oceans, where they are taken up by aquatic organisms.  Thank you Dr. Ritesh Banerjee School of Biological and Environmental Sciences Shoolini University Village Bajhol, Solan (H.P) +91 8585896326 [email protected]