Biogeochemical Cycles

Biogeochemical Cycles - 1 Class Lecture Goals 1. What are systems? 2. What are biogeochemical cycles? 3. Why are they important? 4. What is common about them? 5. Carbon and nitrogen cycles 6. Focus on the Water Cycle What is a system? • System: a collection of matter, parts, or components which are included inside a specified, often arbitrary, boundary. • Systems often have inputs and outputs. • For dynamic systems, by definition, one or more aspects of the system change with time. – Example of a simple dynamic system: bathtub or your ‘bank’ account. Flux Pool • The boundary of a dynamic system is chosen for convenient conceptual separation for the system Understanding Regional Change: Comparison of 2 lake districts In the readings for today, the Lake District being studied was: 1. Northern Highland Lake District, WI 2. Trout Lake District, WI 3. Yoho River Lake District, WI Answer Now! 0% 0% 0% 1 2 3 10 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, nitrogen, water cycles (but could include all necessary elements for life) What is common amongst them? • Typical exist in all four parts of the Earth System • There are ‘pools’ • Are transformed chemically or biochemically • There are fluxes between the pools • Transformations are important • Transformations can lead to positive and negative consequences Transformations Examples of Transformations 1. Carbon cycle: Organic compounds to CO2 (process: decomposition or fire) 2. Carbon cycle: CO2 to organic compounds (process: photosynthesis) 3. Nitrogen cycle: N2 to NO3 (atmospheric nitrogen to plant utilizable nitrate) (process: N-fixation) 4. Nitrogen cycle: N2 to NH3 (plant utilizable ammonia) (process: Haber-Bosch Industrial N-fixation) 5. Water cycle: Liquid water to water vapor (process: evaporation and evapo-transpiration) 6. Water cycle: Water vapor to liquid water (process: condensation) Carbon Cycle 760 5000 http://www.epa.gov/climatechange/kids/carbon_cycle_version2.html Changes in Atmospheric C02 - 1 Dr. Pieter Tans, NOAA/ESRL (www.esrl.noaa.gov/gmd/cgg/trends) Changes in Atmospheric C02 - 2 http://www.whrc.org/resources/online_publications/warming_earth/scientific_evidence.htm Key Aspects of the Carbon Cycle • Carbon is the skeleton of all life. • Carbon dioxide is a critical gas: – Taken up by plants in photosynthesis – Released by plants and animals in respiration – Released during decomposition (and fires) – Greenhouse gas (greenhouse effect - your car in the sun) Question: Photosynthesis is an example of a pool 1. True 2. False 0% 1 0% 2 Answer Now! 10 Nitrogen Cycle Forms & Nitrogen from system Losses Sources Forms ofof nitrogenof biologically available nitrogen 1. N2 - inert gas, 78% of the atmosphere For bogs, NO2 - other of low oxygen), NO3- directly • NO, N20, 2. Inplants lakes (placesgases of nitrogen, not is converted • to N3- by bacteria (get their oxygen gasesthe NO3) NO 2 biologically important. Part of the from found in • Volatilization of NH4+ (urea) to ammonia gas (NH3) NH4+ smog. • warm,and conditions. forms of nitrogen that are 3. Sources: N-fixation by plants (N2 to NH3 and N2 to NO3), NO3- dry NH4+ -- ionic • lightening, bacteria decomposition of organic N (amino Leaching of NO3- (nitrate) biologically usable. • acids & proteins) Erosion • Fire (combustion) For animals • Organic forms: amino acids and proteins (from plants or other animals) http://soil.gsfc.nasa.gov/NFTG/nitrocyc.htm Nitrogen Sources over time Nitrogen Cycle: Key Points • Nitrogen is in the atmosphere as N2 (78%) • N2 is an inert gas and cannot be used by plants or animals • N2 can be converted to a usable form via – Lightening – N-fixing plants and cyanobacteria – Industrial process • Nitrogen limits plant growth Summary • • • • • 1. What are systems? 2. What are biogeochemical cycles? 3. Why are they important? 4. What is common about them? 5. Carbon and nitrogen cycles