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GEOL 1070 Global Change 2 READING ASSIGNMENT 3/07/01 3/7-3/12 Nitrogen page 1 of 6 and Phosphorus Assigned Reading: 1) Xeroxes: Nitrogen and Phosphorous cycle overviews (2 pages text, 2 figures) Phosphorous in Lake Erie (1 page) 2) Env. Sci.: p. 66-70, 49-50, and 421-422 What to know (from readings and class) * the major chemical forms of nitrogen * that nitrogen is an essential element for humans (amino acids), how humans get nitrogen * the processes in the nitrogen cycle, and which processes are facilitated by microorganisms * the main reservoir of nitrogen * the species of nitrogen involved in acid rain * the main anthropogenic source of nitrogen in acid rain * the species of nitrogen involved in stratospheric ozone depletion * the species of nitrogen involved in eutrophication * the species of nitrogen involved in blue baby syndrome * the major chemical forms of phosphorus * the species of phosphorus involved in eutrophication * two main anthropogenic sources of phosphate Vocabulary See next page Vocabulary page 2 of 6 dinitrogen N2 ammonia NH3 ammonium ion NH4+ nitrite NO2nitrate NO3nitrous oxide N2O nitric acid HNO3 NOx nitrogen fixation industrial fixation nitrification denitrification ammonification oxidation acid rain buffer liming essential nutrient eutrophication blue baby syndrome (methaemogloninaemia) phosphate PO43apatite Ca5(PO4)3(F,Cl, OH) GEOL 1070 Global Change 2 READING, NITROGEN CYCLE OVERVIEW page 3 of 6 Modified slightly from: http://www.britannica.com nitrogen cycle circulation of nitrogen in various forms through nature. Nitrogen, a component of proteins and nucleic acids, is essential to life on Earth. Although 78 percent by volume of the atmosphere is nitrogen gas, this abundant reservoir exists in a form unusable by most organisms. Through a series of microbial transformations, however, nitrogen is made available to plants, which in turn ultimately sustain all animal life. The steps, which are not altogether sequential, fall into the following classifications: nitrogen fixation, nitrogen assimilation, ammonification, nitrification, and denitrification. Nitrogen fixation, in which nitrogen gas is converted into inorganic nitrogen compounds, is mostly (90 percent) accomplished by certain bacteria and blue-green algae (see nitrogen fixation). A much smaller amount of free nitrogen is fixed by abiotic means (e.g., lightning, ultraviolet radiation, electrical equipment) and by conversion to ammonia through the Haber-Bosch process. Nitrates and ammonia resulting from nitrogen fixation are assimilated into the specific tissue compounds of algae and higher plants. Animals then ingest these algae and plants, converting them into their own body compounds. The remains of all living things--and their waste products--are decomposed by microorganisms in the process of ammonification, which yields ammonia. (Under anaerobic, or oxygen-free, conditions foul-smelling putrefactive products may appear, but they too are converted to ammonia in time.) Ammonia can leave the soil or be converted into other nitrogen compounds, depending in part on soil conditions. Nitrification, a process carried out by nitrifying bacteria, transforms soil ammonia into nitrates, which plants can incorporate into their own tissues. Nitrates also are metabolized by denitrifying bacteria , which are especially active in water-logged, anaerobic soils. The action of these bacteria tends to deplete soil nitrates, forming free atmospheric nitrogen. GEOL 1070 Global Change 2 READING, NITROGEN CYCLE DIAGRAM page 4 of 6 Source: Environmental Chemistry, 2nd Edition, O'Neill, P., 1993 GEOL 1070 Global Change 2 READING, PHOSPHORUS CYCLE OVERVIEW Modified slightly from: http://www.britannica.com page 5 of 6 phosphorus cycle circulation of phosphorus in various forms through nature. Of all the elements recycled in the biosphere, phosphorus is the scarcest and therefore the one most limiting in any given ecological system. It is indispensable to life, being intimately involved in energy transfer and in the passage of genetic information in the deoxyribonucleic acid (DNA) of all cells. Much of the phosphorus on Earth is tied up in rock and sedimentary deposits, from which it is released by weathering, leaching, and mining. Some of it passes through freshwater and terrestrial ecosystems via plants, grazers, predators, and parasites, to be returned to those ecosystems by death and decay. Much of it, however, is deposited in the sea, in shallow sediments, where it circulates readily, or in ocean deeps, whence it wells up only occasionally. Phosphorus is brought back to the land through fish harvests and through collection of guano deposited by seabirds. Although there are seasonal pulses of availability, there appears to be a steady loss of phosphorus to the ocean deeps. Because of its high reactivity, phosphorus exists in combined form with other elements. Microorganisms produce acids that form soluble phosphate from insoluble phosphorus compounds. The phosphates are utilized by algae and terrestrial green plants, which in turn pass into the bodies of animal consumers. Upon death and decay of organisms, phosphates are released for recycling. Because of the steady diversion of phosphorus into the oceans, the element must be added (in fertilizers) to soils to maintain fertility and agricultural productivity. PHOSPHORUS CYCLE DIAGRAM Source: Environmental Chemistry, 2nd Edition, O'Neill, P., 1993 page 6 of 6 Single page Xerox on restoration of Lake Erie ecosystems (Handed out in class, See Dr. Lubinski for copy)