Total_inorganic_carbon

"Present day" (1990s) sea surface DIC concentration (from the GLODAP climatology)

The total inorganic carbon (C_T, or TIC) or Dissolved inorganic carbon (DIC) is the sum of inorganic carbon species in a solution. The inorganic carbon species include carbon dioxide, carbonic acid, bicarbonate anion, and carbonate anion. It is customary to express carbon dioxide and carbonic acid simultaneously as CO₂* . C_T is an important parameter when making measurements related to the pH of natural aqueous systems, and carbon dioxide flux estimates.

C_T = [CO₂*] + [HCO₃⁻] + [CO₃²⁻]

where,

• C_T is the total inorganic carbon
• [CO₂*] is the sum of carbon dioxide and carbonic acid concentrations ( [CO₂*] = [CO₂] + [H₂CO₃])
• [HCO₃⁻] is the bicarbonate concentration
• [CO₃²⁻] is the carbonate concentration

Each of these species are intimately related by the following pH driven chemical equilibria:

CO₂ + H₂O $\backslash rightleftarrows$ H₂CO₃ $\backslash rightleftarrows$ H⁺ + HCO₃⁻ $\backslash rightleftarrows$ 2H⁺ + CO₃²⁻

Total inorganic carbon is measured by the acidification of the sample which drives the equilibria to CO₂. This gas is then sparged from solution and trapped, and the quantity trapped is then measured, typically by infrared spectroscopy.

See also

• Total Organic Carbon
• Total Alkalinity(A_T)
• pH
• carbon dioxide fugacity(f_CO2)
• Total Organic Carbon Analyzer

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