The Global Carbon Cycle Recording the Evolution of Earth, from the origin of life to the industrialization of the planet

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Austin Boyd
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1 The Global Carbon Cycle Recording the Evolution of Earth, from the origin of life to the industrialization of the planet Celebrating 5 years of world-leading collaborative and multidisciplinary research

7 Carbon Dioxide Concentrations are Increasing... Mauna Loa Observatory, Scripps

8 Atmospheric Carbon Dioxide Atmospheric Methane Glacial Interglacial Cycles

11 Quick Overview of the Carbon Cycle

12 Carbon in the oceanatmosphere system Organic carbon Biological carbon Inorganic carbon Dissolved species: CO 2, CO 3 2- But also calcium carbonate (limestone)

13 Reservoir sizes in Gt C (not Gt CO 2 ) = petagram (Pg) = 1x10 15 g Fluxes in Gt C yr -1

14 The natural short -term carbon cycle Volcanoes and Weathering of Shale Atmosphere (597) Terrestrial biota, soils (2300) IPCC (2007) Surface ocean (900) Deep ocean (37,100) Biota (3) 0.2 Sediment (150)

15 The natural long -term carbon cycle Ocean-Atmosphere-Biosphere Total carbon = 41,000 Gt Cycled between reservoirs very quickly (geologically-speaking) Fluxes <0.5 Gt yr -1 Solid Earth Millions Gt Carbon

16 Many of our interests and challenges are about the long-term carbon cycle or about perturbations to it. So why are we going to talk about the short-term carbon cycle?

17 Organic Carbon is largely about photosynthesis and respiration (i.e. oxygen and light)

18 Carbon Dioxide Concentrations are Increasing... Mauna Loa Observatory, Scripps

19 Redox Chemistry Life needs two things: Energy A way to reduce CO 2 to form biomass Redox potential Reflects the flow of electrons from one atom or molecule to another Thus can be considered as two reactions Oxidation and Reduction This can generate energy (DG) or electrical potential (Eh) DG o (Gibbs free energy) By convention negative values indicate that products are favoured in equilibrium Energy is available if a solution is not in equilibrium

20 Thermodynamics What is the equilibrium distribution of compounds? DG o = -RT lnk, where K = where K ~ gc c x gd d ga a x gb b [C] c [D] d [A] a [B] b aa + bb for cc + dd Thermodynamic energy is available when compounds are not in equilibrium DG = -RT ln K Q = DG o + RT lnq

21 Kinetics Rate = k[a][b] k is defined by the Arrhenius equation k = Ae -E a/rt Where: A = Maximum rate of reaction E a = Activation energy Activation Energy: For any reaction to occur, there must be collisions between species; however at close distances, most species show mutual repulsion. This acts as an energy barrier to the reaction that must be overcome.

22 Photosynthesis Primary production by photosynthesis: 106CO NO 3- + HPO H 2 O + 18H + + trace metals (Fe, Zn, Cu, Cd, Co) C 106 H 263 O 110 N 16 P + 138O 2 Light In terms of Redox: CO 2 + H 2 O CH 2 O + O 2 HNO 3 + H 2 O NH O 2 In terms of Chemical Compounds, roughly: CH 2 O = Carbohydrate NH 3 = Amine (Amino Acid = Protein) PO 4 = DNA, RNA, Membrane lipids

23 What governs Photosynthesis?

24 What governs Photosynthesis?

25 What governs Photosynthesis? From: Sarmiento and Gruber (2006) Ocean Biogeochemical Dynamics, Princeton University Press

26 Respiration Heterotroph: organism that cannot synthesise all the organic molecules it needs using only inorganic compounds; instead they oxidise organic carbon to carbon dioxide to yield cellular energy (respiration) CH 2 O + O 2 CO 2 + H 2 O (CH 2 O) 106 (NH 3 ) 16 H 3 PO O CO H 2 O + 16 HNO 3 + H 3 PO 4

27 What controls Respiration? Aerobic Respiration CH 2 O + O 2 CO 2 + H 2 O DG Denitrification 5 CH 2 O + 4NO H + 5CO 2 + 2N 2 + 7H 2 O Sulfate Reduction 2 CH 2 O + SO HCO H 2 S Methanogenesis 2 CH 2 O CO 2 + CH 4 Hydrogen Fermentation CH 2 O + H 2 O CO 2 + 2H Two take-home messages: Lots of oxidants (but O 2 the best) Strong interactions between carbon and other element cycles

28 What controls Respiration? Rate = k[a][b] k is defined by the Arrhenius equation k = Ae -E a/rt Where: A = Maximum rate of reaction E a = Activation energy Activation Energy: For any reaction to occur, there must be collisions between species; however at close distances, most species show mutual repulsion. This acts as an energy barrier to the reaction that must be overcome.

29 But why doesn t everything degrade.. eventually? As thermodynamics says it should?

30 Reservoir sizes in Gt C (not Gt CO 2 ) = petagram (Pg) = 1x10 15 g Fluxes in Gt C yr -1

31 The inorganic carbon cycle is basically about ph

32 When CO 2 dissolves in water, it is an acid Dissolved Inorganic Carbon occurs as several dissolved species CO 2 (aq) + H 2 O H 2 CO 3 H 2 CO 3 H + + HCO 3 - HCO 3 - H + + CO 3 2- SCO 2 = Total DIC = CO 2 (aq) + H 2 CO 3 + HCO CO 3 2-

33 Ca 2+ + CO 2-3 CaCO 3 (s)

34 Ca 2+ + CO 2-3 CaCO 3 (s)

37 CO 2(aq) + CaCO 3 (s) + H 2 O Ca HCO 3 -

38 CO 2(aq) + CaCO 3 (s) + H 2 O Ca HCO 3 -

39 Reservoir sizes in Gt C (not Gt CO 2 ) = petagram (Pg) = 1x10 15 g Fluxes in Gt C yr -1

41 So what is the global carbon cycle about? Life!! Life s origin and its evolution Photosynthesis and Respiration The history of carbon dioxide and of methane The formation of oil and coal The industrial age, fossil fuels and global warming The deep biosphere and exotic organisms The fate of permafrost and soil The things that vary with carbon redox reactions nutrients in the ocean to toxic metal contamination

XI. the natural carbon cycle. with materials from J. Kasting (Penn State)

XI. the natural carbon cycle. with materials from J. Kasting (Penn State) XI. the natural carbon cycle with materials from J. Kasting (Penn State) outline properties of carbon the terrestrial biological cycle of carbon the ocean cycle of carbon carbon in the rock cycle overview