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Carbon Cycle Carbon Carbon exists in the nonliving environment as: • • • • • Carbon dioxide (CO2) Carbonic acid ( HCO3−) Carbonate rocks (limestone and coral = CaCO3) Deposits of Fossil fuels Dead organic matter Organic Carbon • Hydrocarbons: CH4 • Carbohydrate: CH2O • lipids • Other molecules Inorganic carbon • Carbon Dioxide: CO2 • Calcium Carbonate: CaCO3 Mandale Limestone Quarry Carbon Fixation The conversion process of inorganic carbon (carbon dioxide) to organic compounds by living organisms. Autotrophs absorb CO2 from atmosphere • Convert to carbohydrates, lipids & other carbon compounds • Reduces CO2 in atmosphere • Average concentration is 0.039% ???? • Why is the concentration of CO2 lower above parts of the earth’s surface where photosynthesis rates are high? • Where are these locations? ????? • Discuss with a neighbor how removing the rain forests would affect global CO2 levels. Carbon is removed from the atmosphere in several ways • Photosynthesis. • The oceans when the seawater becomes cooler, more CO2 dissolve and become carbonic acid. (ocean pH reduced) Consequences???? • In the upper ocean areas organisms convert reduced carbon to carbohydrates & other compounds. Autotrophs absorb CO2 from atmosphere • Autotrophs utilize CO2. • Creates concentration gradient between cells <->atmosphere • Diffuses high to low • Stomata in plants Photosynthesis • CO2 + H2O + sunlight CH2O + O2 CO2 in solutions • Dissolves in water forming carbonic acid • CO2 + H2O carbonic acid hydrogen + carbonate ions • pH reduced • Carbon carbohydrates, other Carbon is released into the atmosphere in several ways • Respiration by plants and animals. • Decay of animal and plant matter. • Combustion of organic material • Production of cement. • The ocean releases CO2 into the atmosphere. • Volcanic eruptions and metamorphism Respiration • • • • • CO2 – aerobic waste product Non-photosynthetic root cells Animal cells Saprotrophs Diffuses out of cells into atmosphere & water Respiration • CH2O + O2 CO2 + H2O + energy Methanogenesis • the formation of methane by microbes known as methanogens. • Organisms capable of producing methane have been identified only from the domain Archaea Methanogensisis • Bacteria organic matter organic acids, alcohols, H2, CO2 • Bacteria organic acids + alcohols acetate, H2, CO2 • Archaeans produce CH4 from acetate, H2, & CO2 • Mud & swampy areas • Guts of cattle, sheep • Buried organic material ?????? • As permafrost melts due to increasing global temperatures explain the impact on CO2 levels. • Be able to support your reasoning. Oxidation of methane • Methane released into atmosphere is oxidized and converted to carbon dioxide and water • 12 years Combustion • Organic matter that burns in the presence of oxygen produces carbon dioxide and water • Forest fires & other biomass • Natural causes • Burning of rain forests for farm land • Burning of fossil fuels Combustion or Oxidization of hydrocarbon CH4 + 2 O2 CO2 + 2 H2O + energy CH4 + O + OH˙ CO2 + H2O Limestone • Animals containing calcium carbonate that become fossilized form limestone • Mollusc shells • Hard corals • Deposits form in sea beds • 10% of sedimentary rock • 12% of the mass of calcium carbonate is carbon Peat formation • • • • • Incomplete decomposition Anaerobic conditions Water logged – saprotrophs cannot thrive Acidic conditions Peat: dark brown, acidic, incompletely decomposed organic matter • 3% of Earth’s surface – up to 10 meters, bogs Fossilized organic matter • Coal- peat buried under sediments, compressed, heated • Pennsylvanian sub-period of Carboniferous • Sea level rose & fell • Oil & natural gas- sea & lake mud • Anaerobic conditions, incomplete decomposition • Organic material buried, forms mixtures of liquid carbon compounds & gases (methane) Fossil Fuels •Petroleum •Natural Gas •Coal Fossil Fuel 86% of global primary energy consumption is fossil fuels. Human Impacts on the Carbon Cycle Burning fossil fuels have serious impact on the carbon cycle. Carbon reservoirs •The atmosphere. •The biosphere •The oceans •The lithosphere (include fresh water systems and non-living organic material, such as soil carbon). ( including dissolved inorganic carbon and living and non-living marine biota). (sediments, Earth core including fossil fuels) . Carbon reservoirs Carbon Cycle Draw Carbon Cycle combustion CO2 Concentration Pre-Industrial value: 280 ppm (600 billion tons) Current value: 380 ppm (800 billion tons) Critical value: 560 ppm (1200 billion tons) Keeling Curve