Carbon dioxide in Earth's atmosphere atmosphere, oceans, soil, rocks, and volcanism. Both carbon cycles are intrinsically interconnected and atmospheric gaseous carbon dioxide facilitates the carbon cycle. Natural sources of atmospheric carbon dioxide include volcanic outgassing, the combustion of organic matter, wildfires and the respiration processes of living aerobic organisms. Man-made sources of carbon dioxide include the burning of fossil fuels for heating, power generation and transport, as well as some industrial processes such as cement making. It is also produced by various microorganisms from fermentation and cellular respiration. Plants, algae and cyanobacteria convert carbon dioxide to carbohydrates by a process called photosynthesis. They gain the
Carbon dioxide stretching mode at 1388 cm which is only observed in the Raman spectrum. Carbon dioxide is soluble in water, in which it reversibly forms (carbonic acid), which is a weak acid since its ionization in water is incomplete. The hydration equilibrium constant of carbonic acid is formula_1 (at 25 °C). Hence, the majority of the carbon dioxide is not converted into carbonic acid, but remains as molecules, not affecting the pH. The relative concentrations of , and the deprotonated forms (bicarbonate) and (carbonate) depend on the pH. As shown in a Bjerrum plot, in neutral or slightly alkaline water (pH