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Explore the basics of biogeochemical cycles involving water, carbon, nitrogen, sulfur, phosphorus, and oxygen. Learn about the interconnected cycles and spheres, human impacts, and the importance of the carbon cycle. Delve into the nitrogen cycle sources, forms, reservoirs, roles, and cycles.
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Anton Cwik, Ethan Sox Per. 4
‘Fundamentals’ of biogeochemical cycles • All matter cycles...it is neither created nor destroyed... • As the Earth is essentially a closed system with respect to matter, we can say that all matter on Earth cycles . • Biogeochemical cycles: the movement (or cycling) of matter through a system
by matter we mean: elements (carbon, nitrogen, oxygen) or molecules (water) so the movement of matter (for example carbon) between these parts of the system is, practically speaking, a biogeochemical cycle The Cycling Elements: macronutrients : required in relatively large amounts "big six": carbon , hydrogen , oxygen , nitrogen , phosphorous sulfur
other macronutrients: potassium , calcium , iron , magnesium micronutrients : required in very small amounts, (but still necessary) boron (green plants) copper (some enzymes) molybdenum (nitrogen-fixing bacteria)
6 of the most important cycles are the water, carbon, nitrogen, sulfur, phosphorus and oxygen.
1. Which part of the atmosphere has the highest altitude?A. Troposphere B. Stratosphere C. Thermosphere D. Mesosphere2. Which part includes all three of the other parts?Lithosphere B. Ecosphere C. Hydrosphere D. Atmosphere3. Which one is not a major cycle?A. Hydrogen B. Nitrogen C. Oxygen D. Sulfur E. Water
HYDROLOGIC CYCLE CONNECTS ALL OF THE CYCLES AND SPHERES TOGETHER
HUMAN IMPACTS TO WATER CYCLE • Water withdrawal from streams, lakes and groundwater. (salt water intrusion and groundwater depletion) • Clear vegetation from land for agriculture, mining, road and building construction. (nonpoint source runoff carrying pollutants and reduced recharge of groundwater) • Degrade water quality by adding nutrients(NO2, NO3, PO4) and destroying wetlands (natural filters). • Degrade water clarity by clearing vegetation and increasing soil erosion.
Carbon in Oceans • Additional carbon is stored in the ocean. • Many animals pull carbon from water to use in shells, etc. • Animals die and carbon substances are deposited at the bottom of the ocean. • Oceans contain earth’s largest store of carbon.
IMPORTANCE OF CARBON CYCLE CARBON IS THE BACKBONE OF LIFE!
1. What is no part of the water cycle?A. Precipitation B. Percolation C. Transpiration D. Surface Runoff E. Boiling2. Which is not a man made way of adding carbon to the carbon cycle?A. Airplanes B. Natural Fires C. Cars D. Burning fossil fuels3. What are the predictions for how much carbon will be added from fossil fuels?A. Low B. Medium-Low C. Medium D. High
Sources • Lightning • Inorganic fertilizers • Nitrogen Fixation • Animal Residues • Crop residues • Organic fertilizers
Forms of Nitrogen • Urea CO(NH2)2 • Ammonia NH3 (gaseous) • Ammonium NH4 • Nitrate NO3 • Nitrite NO2 • Atmospheric Dinitrogen N2 • Organic N
Roles of Nitrogen • Plants and bacteria use nitrogen in the form of NH4+ or NO3- • It serves as an electron acceptor in anaerobic environment • Nitrogen is often the most limiting nutrient in soil and water.
Nitrogen is a key element for • amino acids • nucleic acids (purine, pyrimidine) • cell wall components of bacteria (NAM).
Nitrogen Cycles • Ammonification/mineralization • Immobilization • Nitrogen Fixation • Nitrification • Denitrification
N2 N2O NH4 NO2 R-NH2 NO NO2 NO3
Which of the following is not part of the Nitrogen Cycle? A) Ammonification B) Nitrification C) Denitrosation D) Nitrogen Fixation E) Denitrification In what form(s) do plants and bacteria use nitrogen? A) NH4+ B) NH3 C) NO3- D) A and C E) All of the above What is the molecular formula for ammonium? A) NH4+ B) NH3 C) NO3 D) NO2 E) none of the above
Ammonification or Mineralization N2 N2O NH4 NO2 R-NH2 NO NO2 NO3
Mineralization or Ammonification • Decomposers: earthworms, termites, slugs, snails, bacteria, and fungi • Uses extracellular enzymes initiate degradation of plant polymers • Microorganisms uses: • Proteases, lysozymes, nucleases to degrade nitrogen containing molecules
Plants die or bacterial cells lyse release of organic nitrogen • Organic nitrogen is converted to inorganic nitrogen (NH3) • When pH<7.5, converted rapidly to NH4 • Example: Urea NH3 + 2 CO2
Immobilization • The opposite of mineralization • Happens when nitrogen is limiting in the environment • Nitrogen limitation is governed by C/N ratio • C/N typical for soil microbial biomass is 20 • C/N < 20Mineralization • C/N > 20 Immobilization
Nitrogen Fixation N2 N2O NH4 NO2 R-NH2 NO NO2 NO3
Nitrogen Fixation • Energy intensive process : • N2 + 8H+ + 8e- + 16 ATP = 2NH3 + H2 + 16ADP + 16 Pi • Performed only by selected bacteria and actinomycetes • Performed in nitrogen fixing crops (ex: soybeans)
Azobacter Beijerinckia Azospirillum Clostridium Cyanobacteria Require the enzyme nitrogenase Inhibited by oxygen Inhibited by ammonia (end product) Microorganisms fixing
Immobilization is the opposite of which process in the cycle? A) Mineralization B) Nitrification C) Immobilization D) Nitrogen Fixation E) Denitrification What process takes place when nitrogen is limiting in the environment? A) Mineralization B) Nitrification C) Immobilization D) Nitrogen Fixation E) Denitrification Which has the highest rate of nitrogen fixation? A) Rhizobium-legume B) Cynaobacteria-moss C) Rhizosphere associations D) Free-living E) Azobacter
Applications to wetlands • Occur in overlying waters • Aerobic soil • Anaerobic soil • Oxidized rhizosphere • Leaf or stem surfaces of plants
Bacterial Fixation • Occurs mostly in salt marshes • Is absent from low pH peat of northern bogs • Cyanobacteria found in waterlogged soils
Nitrification N2 N2O NH4 NO2 R-NH2 NO NO2 NO3
Nitrification Two step reactions that occur together : • 1rst step catalyzed by Nitrosomonas 2 NH4+ + 3 O2 2 NO2- +2 H2O+ 4 H+ • 2nd step catalyzed by Nitrobacter • 2 NO2- + O2 2 NO3-
Optimal pH is between 6.6-8.0 • If pH < 6.0 rate is slowed • If pH < 4.5 reaction is inhibited In which type of wetlands do you thing Nitrification occurs?
Denitrification N2 N2O NH4 NO2 R-NH2 NO NO2 NO3
Denitrification • Removes a limiting nutrient from the environment • 4NO3- + C6H12O6 2N2 + 6 H20 • Inhibited by O2 • Not inhibited by ammonia • Microbial reaction • Nitrate is the terminal electron acceptor