Sulfur cycle
The movement of sulfur among rocks, oceans, atmosphere, soil, and organisms through geological, chemical, and biological processes.
Sulfur oxidation: The chemical or biological conversion of reduced sulfur compounds into more oxidized forms. Microbes and chemical reactions oxidize sulfide and elemental sulfur, making sulfate available in many environments.
Fossil fuel combustion: The burning of coal, oil, or natural gas to release usable energy. Combustion releases sulfur compounds that had been stored in geological deposits.
Sulfur: A chemical element with atomic number 16 that occurs in minerals, dissolved ions, gases, and organic compounds. Its chemical versatility allows sulfur to move among the cycle’s many compounds and reservoirs.
Hydrothermal vent: A seafloor opening that emits heated, chemically altered water from Earth’s crust. Vents release reduced sulfur compounds that fuel distinctive microbial food webs.
Sulfur limitation: Restricted biological growth caused by insufficient availability of sulfur compounds. When sulfur is scarce, its uptake can constrain plant and microbial production.
Sulfate reduction: The conversion of sulfate into reduced sulfur compounds, often by microorganisms using it in anaerobic respiration. This process returns sulfur in sediments and wetlands to reduced forms such as sulfide.
Flue-gas desulfurization: Technologies that remove sulfur dioxide from exhaust gases, commonly using alkaline sorbents. These systems interrupt a major industrial route from fossil sulfur to atmospheric pollution.
Sulfate: The sulfur oxyanion SO₄²⁻, abundant in seawater and a major form of sulfur in soils. Sulfate is the principal dissolved sulfur form taken up by many organisms.
Sulfur-oxidizing bacteria: Bacteria that obtain energy by oxidizing reduced sulfur compounds. They convert vent sulfide and other reduced sulfur into forms that support local ecosystems.
Dimethyl sulfide: A volatile sulfur compound, (CH₃)₂S, produced by marine organisms and other biological sources. Its oxidation forms marine aerosols and helps connect ocean biology with atmospheric chemistry.