Total inorganic carbon


Total inorganic carbon is the sum of inorganic carbon species.
Carbon compounds can be distinguished as either organic or inorganic, and dissolved or particulate, depending on their composition. Organic carbon forms the backbone of key component of organic compounds such as – proteins, lipids, carbohydrates, and nucleic acids. Inorganic carbon is found primarily in simple compounds such as carbon dioxide, carbonic acid, bicarbonate, and carbonate.

Inorganic carbon species

The inorganic carbon species include carbon dioxide, carbonic acid, bicarbonate anion, and carbonate. It is customary to express carbon dioxide and carbonic acid simultaneously as CO2*. CT is a key parameter when making measurements related to the pH of natural aqueous systems, and carbon dioxide flux estimates.
where,
Each of these species are related by the following pH-driven chemical equilibria:
The concentrations of the different species of DIC depends on the pH of the solution, as shown by a Bjerrum plot.
Total inorganic carbon is typically 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, usually by infrared spectroscopy.

Marine carbon

Marine carbon is further separated into particulate and dissolved phases. These pools are operationally defined by physical separation – dissolved carbon passes through a 0.2 μm filter, and particulate carbon does not.
There are two main types of inorganic carbon that are found in the oceans:
Some of the inorganic carbon species in the ocean, such as bicarbonate and carbonate, are major contributors to alkalinity, a natural ocean buffer that prevents drastic changes in acidity. The marine carbon cycle also affects the reaction and dissolution rates of some chemical compounds, regulates the amount of carbon dioxide in the atmosphere and Earth's temperature.