Biogeochemical Cycles - 1 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. Example: Ecosystem 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 The boundary of a dynamic system is chosen for convenient conceptual separation for the system Pool

Carbon dioxide C-pool Sugar Night

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 and water cycles (but could include all necessary elements for life). N - cycle weakly touched on!

What is common amongst them? Each compound (water, carbon, nitrogen) typically exists in all four parts of the Earth System There are ‘Pools’ Fluxes in and out of pools Chemical or biochemical transformations Transformations are important can lead to positive & negative consequences

Transformations Examples of Transformations Carbon cycle: Organic compounds to CO2 (processes: respiration, decomposition, or fire) Carbon cycle: CO2 to organic compounds (process: photosynthesis) Nitrogen cycle: N2 to NO3 (atmospheric nitrogen to plant utilizable nitrate) (process: N-fixation) Nitrogen cycle: N2 to NH3 (plant utilizable ammonia) (process: Haber-Bosch Industrial N-fixation) Water cycle: Liquid water to water vapor (process: evaporation and evapo-transpiration) Water cycle: Water vapor to liquid water (process: condensation)

Carbon Cycle 5000 http://www.epa.gov/climatechange/kids/carbon_cycle_version2.html

Carbon Cycle Data Burning of fossil fuels Land conversion Cement 760 59 Burning of fossil fuels Land conversion Cement Role of Oceans Role of terrestrial plants (trees & soils) Lithosphere

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)

Nitrogen Cycle Forms of Nitrogen (N2) N2 - inert gas, 78% of the atmosphere NO, N20, NO2 - other gases of nitrogen, not directly biologically important. Part of the gases found in smog. NO3- (nitrate) and NH4+ (ammonium) -- ionic forms of nitrogen that are biologically usable. http://soil.gsfc.nasa.gov/NFTG/nitrocyc.htm

Nitrogen Cycle Forms & Sources of biologically available nitrogen (N2) For plants NO3- (nitrate) NH4+ (ammonium) Sources: N-fixation by plants (N2 to NH3 and N2 to NO3), lightening, bacteria decomposition of organic N (amino acids & proteins) For animals Organic forms: amino acids and proteins (from plants or other animals) http://soil.gsfc.nasa.gov/NFTG/nitrocyc.htm

Nitrogen Cycle Losses of nitrogen from system In bogs, lakes (places of low oxygen), NO3- is converted to N2 by bacteria (get their oxygen from the NO3) Volatilization of NH4+ (urea) to ammonia gas (NH3) - warm, dry conditions. Leaching of NO3- (nitrate) Erosion Fire (combustion) 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 (energy intensive) Nitrogen limits plant growth Nitrogen is easily lost from biological systems

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