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Chemical Reservoir 1 What is a chemical reservoir a Body of chemical entity that occupies a particular space b Reservoirs are not closed c Chemicals move from reservoir to reservoir in cycles d Expand and contract through changes in rates at which chemicals flow to or from them 2 What is chemical flux a Rate at which chemicals flow from one reservoir to another b Change on flux some reservoirs expand while others contract c Change to Earth with particular consequences for the planet and its life 3 Feedback affects fluxes a Negative opposes changes b Positive accelerates changes 4 If the atmospheric concentration of CO2 is increased a Negative feedback solar insulation plants b Positive feedback global warming c Major players i Biosphere ii Hydrosphere iii Cryosphere iv Lithosphere v Atmosphere d Plants prolitherate because more CO2 to use for photosynthesis e Carbon stored as biomass f Increased forest coverage g Lower albedo as compared to tundra h More heat absorption i Acceleration of global warming CO2 and O2 1 Living things play major roles in chemical cycles within the earth system via photosynthesis and respiration Important raw materials a i Water ii Carbon dioxide 2 Photosynthesis produces plant tissues a Photosynthesis the creation of sugar b Respiration the burning of sugar c Plant tissue biomass reservoir i CO2 and H2O used are temporarily sequestered in the biomass reservoir 3 Photosynthesis respiration cycle between plants and animals 4 Respiration and decomposers 5 Double the biomass doubles the O2 and CO2 flux a Atmospheric reservoir volume remains the same 6 Burial of organic carbon a Carbon is not returned to atmospheric reservoir by respiration process recycling is buried or if not decomposed 7 Marine cycling resembles terrestrial cycling a Hypoxic waters i GOM Dead Zones Carbon Isotopes 1 How can we reconstruct fluxes of carbon from atmosphere to the biosphere to the lithosphere during geologic past a Stable isotopes i Don t have half lives ii Carbon isotope ratios record cycling of organic carbon between reservoirs 2 Plants preferentially use lighter carbon CO2 from atmosphere for photosynthesis a Rapid burial of organic carbon disproportionally buries more carbon12 locked in plant tissues b Causes the remaining CO2 in the atmosphere to become more concentrated in carbon13 3 Carbon isotopes record cycling of organic carbon between reservoirs 4 Weathering of rock consumes atmospheric CO2 a Rain H2O atmospheric CO2 carbonic acid H2CO2 b Carbonic rain weathers CaO3 and silicate rocks exposed at surface c Dissolved ions carried by rivers to oceans then inorganically or organically precipitate d Limestone is stored for a long period carbon is consumed in the rock reservoir atmosphere e Carbon can then be released from the lithosphere and returned to the If the platform or pelagic carbonate undergoes MM i ii And or partial melting collision zone 5 Changes in rates of weathering affect the atmospheric carbon reservoir 6 Weathering rates influenced by a Mountain building chemical weathering consumes atmospheric CO2 b Temperatures increased temperature increased weathering c Precipitation increased moisture increased weathering d Vegetation root acids weather rock 7 Effectively negative feedback Phanerozoic Trends 1 CO2 trends during Phanerozoic a Paleozoic Era i Devonian sharp decrease on CO2 1 Cause 1st ever widespread inland expansion of forests a Root acid greatly increased rock weathering consuming CO2 ii Carboniferous continued additional CO2 decrease 1 Cause increased burial of organic carbon in coal swamps a Burial of organics draws CO2 out of atmosphere b Long term decrease in CO2 c Mesozoic Era CO2 removal i Triassic decrease mountain building associated reduction in ii Evolution of calcareous nannoplankton and forams 1 Subduction of carbonates produced CO2 release back into the atmosphere Oxygen Isotopes 1 Oxygen isotope ratios also fluxuate a Most common oxygen16 and oxygen18 b Marine organisms incorporate the oxygen isotopes into their shells CaCO3 c Change ratios in fossilized shells indicate change 2 Modern studies show that oxygen isotopic ratios measured as d18O in marine shells depends on 3 factors a Ocean water temperature oxygen18 incorporate b Ocean water salinity oxygen16 lighter and evaportates easier enriching oceans with oxygen18 during increased evaporation c Glacial ice accumulation glaciers preferentially incorporate oxygen16 leaving oxygen18 concentrated Ocean Chemistry 1 MOR ion exchange system a Extract magnesium from seawater release carbon b Lower Mg Ca ratio when ridges are abundant 2 Correlates with sea level change a Increased MOR volume increased sea level

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LSU GEOL 1003 - Chemical Reservoir

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