Presentation on theme: "Carbon Dioxide Sources and Sinks: Respiration and Photosynthesis"— Presentation transcript:
1Carbon Dioxide Sources and Sinks: Respiration and Photosynthesis CO2 + H2O ---hn---> Org-C + O2 (photosynthesis)Org-C + O > CO2 + H2O (respiration)The CO2 system is regulated by the acid/base chemistry of the carbonate system! (pH between )Formation of calcareous sediments (CaCO3)It is time to do some serious chemistry
8Carbonate Mass and Charge Balance Total CO2 = H2CO3 + HCO3- +CO32-Total Alkalinity = HCO3- + 2CO32-Another way of thinking about alkalinity is the charge of permanent cations - charge of permanent anions!
9Lets pull this all together TCO2 = H2CO3 + HCO3- +CO32-TA = HCO3- + 2CO32-pH = -log(H+)
10Lets pull this all together TCO2 = H2CO3 + HCO3- +CO32-TA = HCO3- + 2CO32-pH = -log(H+)
116 Equations, 8 Unknowns Measure two variables to define the system. pH Total AlkalinitypCO2We also need values for K1, K2, K*
15Carbonate Solubility Carbonate (CaCO3) Aragonite (CaCO3) CaCO3 = Ca2+ + CO32-Ksp vs. Ion ProductIP = [Ca2+][CO32-]@ Equilibrium Ksp=IPKsp > IP precipitationKsp < IP dissolutiondiss. produces 2 units of TA, 1 unit TCO2ppt. consumes 2 units of TA, 1 unit TCO2
18How do we mess with the CO2 system Carbonate precipitation or dissolution?diss. produces 2 units of TA, 1 unit TCO2ppt. consumes 2 units of TA, 1 unit TCO2Photosynthesis or Respiration?photo. Consume TCO2, TA = constantrespir. Produce TCO2, TA = constantEvaporation/precipitationChange in TCO2 = TA