Unformatted text preview:

Slide 1BioGEOCHEMICAL CYCLESBIOGEOCHEMICAL CYCLING OF ELEMENTS: examples of major processesHISTORY OF EARTH’S ATMOSPHERESlide 5COMPARING THE ATMOSPHERES OF EARTH, VENUS, AND MARSSlide 7Slide 8Slide 9Slide 10Slide 11Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19FAST OXYGEN CYCLE: ATMOSPHERE-BIOSPHERE…however, abundance of organic carbon in biosphere/soil/ocean reservoirs is too small to control atmospheric O2 levelsSLOW OXYGEN CYCLE: ATMOSPHERE-LITHOSPHERESlide 23GLOBAL PREINDUSTRIAL CARBON CYCLESlide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Chemical Composition of Sea WaterALKALINITY & THE CARBONATE BUFFERSlide 37Inorganic Carbon SpeciesRatios of Carbon SpeciesSlide 40Slide 412. Slow Ocean Turnover RateSlide 43Slide 44Slide 45Slide 46Slide 47NET UPTAKE OF CO2 BY TERRESTRIAL BIOSPHERE (1.4 Pg C yr-1 in the 1990s; IPCC [2001]) is a small residual of large atm-bio exchangeCYCLING OF CARBON WITH TERRESTRIAL BIOSPHERESlide 50EVIDENCE FOR LAND UPTAKE OF CO2 FROM TRENDS IN O2, 1990-2000Slide 52Slide 53Slide 54Slide 55Slide 56Slide 57Slide 58Slide 59Slide 60Slide 61Slide 62Slide 63Slide 64Slide 65Slide 66Slide 67PROJECTIONS OF FUTURE CO2 CONCENTRATIONS [IPCC, 2001]Slide 69Carbon-Climate FuturesSlide 71Slide 72Slide 73Non-CO2 Greenhouse GasesAtmospheric Methane (CH4)‏Slide 76Slide 77Slide 78Slide 79Slide 80Slide 81Slide 82Slide 83Slide 84Slide 85IPCC [2001] Projections of Future CH4 Emissions (Tg CH4) to 2050OXIDATION STATES OF NITROGEN N has 5 electrons in valence shell 9 oxidation states from –3 to +5THE TERRESTRIAL NITROGEN CYCLE: MAJOR PROCESSESSlide 89Slide 90Slide 91BOX MODEL OF THE NITROGEN CYCLEN2O: LOW-YIELD PRODUCT OF BACTERIAL NITRIFICATION AND DENITRIFICATIONSlide 94Slide 95Slide 96Slide 97Slide 98PRESENT-DAY GLOBAL BUDGET OF ATMOSPHERIC N2OBOX MODEL OF THE N2O CYCLESlide 101Slide 102N2O Observed vs Model (EDGAR—2000 )‏Slide 104Slide 105Slide 106Slide 107PROJECTED FUTURE TRENDS IN CO2 UPTAKE BY OCEANS AND TERRESTRIAL BIOSPHERESlide 109Slide 110I. Physical Principles: The foundation & the toolsNewton's laws: forces, pressure, motionEnergy: Temperature, radiant energyII. Atmospheric & Ocean Physics: First element of climate and environmental scienceAtmospheric structure (T, P in "4-D") Winds, Weather, General Circulation, Climate III. Atmospheric & Ocean Biogeochemistry: Second element of climate and environmental scienceAtmospheric and ocean composition, past and presentHuman impact, global change IV. Intersection: what we know, would like to know, will never know, and what can we contribute to the debate.BioGEOCHEMICAL CYCLESBioGEOCHEMICAL CYCLES•Most abundant elements: oxygen (in solid earth!), iron (core), silicon (mantle), hydrogen (oceans), nitrogen, carbon, sulfur…•The elemental composition of the Earth has remained essentially unchanged over its 4.5 Gyr history–Extraterrestrial inputs (e.g., from meteorites, cometary material) have been relatively unimportant –Escape to space has been restricted by gravity•Biogeochemical cycling of these elements between the different reservoirs of the Earth system determines the composition of the Earth’s atmosphere and oceans, and the evolution of lifeTHE EARTH: ASSEMBLAGE OF ATOMS OF THE 92 NATURAL ELEMENTSTHE EARTH: ASSEMBLAGE OF ATOMS OF THE 92 NATURAL ELEMENTSBIOGEOCHEMICAL CYCLING OF ELEMENTS:BIOGEOCHEMICAL CYCLING OF ELEMENTS:examples of major processesexamples of major processesPhysical exchange, redox chemistry, biochemistry are involvedSurfacereservoirsHISTORY OF EARTH’S ATMOSPHEREHISTORY OF EARTH’S ATMOSPHEREOutgassingN2CO2H2Ooceans formCO2dissolvesLife forms in oceansOnset ofphotosynthesisO2O2 reaches current levels; life invades continents4.5 GyB.P4 GyB.P.3.5 GyB.P.0.4 GyB.P.presentSource: EARLY EARTH Oxygen for heavy-metal fans: Lyons TW, Reinhard CTNATURE Volume: 461 Issue: 7261 Pages: 179-181 SEP 10 2009COMPARING THE ATMOSPHERES COMPARING THE ATMOSPHERES OF EARTH, VENUS, AND MARSOF EARTH, VENUS, AND MARS3x10-41x10-23x10-3H2O (atm, mol/mol)1.3x10-30.216.9x10-5O2 (mol/mol)0.0070.6415.98914.87Surface pressure (atm)Mass (1024 kg)2.7x10-20.783.4x10-2N2 (mol/mol)0.953x10-40.96CO2 (mol/mol)340064006100Radius (km)MarsEarth VenusH2O (total, bars) 0.3 400 2 x 10-60.1x10-9Carbonyl Sulfide (COS)3.0x10-9Chlorofluorocarbons 0.03x10-6 to 0.3x10-6Carbon Monoxide (CO)0.32x10-6Nitrous Oxide (N2O)0.55x10-6Hydrogen (H2)1.1x10-6Krypton (Kr)1.7x10-6Methane (CH4)5.2x10-6Helium (He)0.02x10-6 to 10x10 –6Ozone (O3) ¶18.2x10-6Neon (Ne)Carbon Dioxide (CO2)0.0093Argon (Ar)0.04 to < 5x10-3; 4x10-6 -stratWater (H2O)0.21Oxygen (O2)0.78Nitrogen (N2)Mole fractionGasAtmospheric Atmospheric Composition Composition (average)(average)1 ppm= 1x101 ppm= 1x10-6-6red = increased by red = increased by human activityhuman activity¶ Ozone has increased in the troposphere, but decreased in the stratosphere.Arrows indicate El Nino eventsNotice:• atmospheric increase is ~50% of fossil fuel emissions• significant interannual variabilityNOAA Greenhouse Gas recordsUltra-simplified ("toy") model for atmospheric concentrations of CO2, CH4 and other gases:A) mass balance B) Inputs or Production ("P"), controlled by biogeochemical processesC) Removal or Loss ("L"), at a rate proportional to the amount that is present in the atmosphere (1st order or linear process, for example: dissolving CO2 in the ocean, reacting CH4 with atmospheric hydroxyl radical. 1/L = "Lifetime"). Quantity: C gas concentration in the atmosphere (Gtons C, or ppm; 1 ppm = 2.1 Gtons C globally)Ultra-simplified ("toy") model for atmospheric concentrations of CO2, CH4 and other gases:A) mass balance B) Inputs or Production ("P"), controlled by biogeochemical processesC) Removal or Loss ("L"), at a rate proportional to the amount that is present in the atmosphere (1st order or linear process, for example: dissolving CO2 in the ocean, reacting CH4 with atmospheric hydroxyl radical). 1/L = "Lifetime".Quantity: C gas concentration in the atmosphere (Gtons C, or ppm; 1 ppm = 2.1 Gtons C globally)The mass balance equation:Rate of change in the atmosphere = P - L C (units: Gtons/yr)dCdt=P −LCImpulse Approach Steady State Accumulation Airborne FractionResults from a "Toy Model" of human-caused CO2 changeHow is the composition of Earth's atmosphere controlled by geochemical and biological processes ?FAST OXYGEN CYCLE:


View Full Document

HARVARD EPS 5 - Biogeochemical Cycles

Download Biogeochemical Cycles
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Biogeochemical Cycles and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Biogeochemical Cycles 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?