Sulfur Cycle Definition Importance Process and Steps (Diagrams)

Among the natural cycles, one of the most complicated is the sulfur cycle. This chemical compound ofsulfur cycle nomenclature S, is part of the protein content of flora and fauna. For this reason, it is had as elemental sustenance for all living beings. The process to which it is associated undergoes numerous oxidation methods, which allow its circulation in the biosphere. Let’s see how it happens.

What is the sulfur cycle?

The sulfur cycle is a series of biogeochemical phases based on the circulation of these particles through nature. It is one of the chemical circles capable of moving throughout the biosphere. It begins its rotation in the terrestrial subsoil, passes to the flora, then to the fauna and returns to the ground again.

  • What is the sulfur cycle?
  • features
  • Process
  • Stages of the sulfur cycle
  • Alterations of the sulfur cycle
  • Consequences
  • Profits
  • Organisms that participate in the sulfur cycle
  • Importance

The biogeochemical cycle constitutes the journey made by sulfur through nature. It is transported by air, soil, water and living entities. Allows chemical component particles to change with rain or water.

They are thus restored to the earth again, as acid degradation and can be absorbed again by plants. This ensures that the cycle begins repeatedly and without setbacks.


Some of the characteristics of the sulfur cycle and its main element are the following:

  • It is chemically complex.
  • It describes the transit of sulfur in its different forms throughout the environment.
  • Includes mineralization of organic sulfur to sulfide.

Sulfur as such has certain features that differentiate it from other minerals:

  • It is a metal of a strange yellow-orange color, close to brown.
  • It is flammable, offering a bluish-colored flame.
  • It has an unpleasant and unmistakable smell similar to a rotten egg.
  • It gives off sulfur dioxide and is not soluble in water.
  • It dissolves in carbon dioxide and benzene.
  • It is tasteless and brittle.
  • It is located in the stones or rocks accumulated by oceanic precipitates.
  • It is produced in the natural environment, either by volcanic eruptions, by bacterial transformations, where organic matter is altered, or by the evaporation of water.


The sulfur cycle is based on the ability of this chemical element to transport itself in dissimilar environments. It begins in the lithosphere , where the salts or esters are located, either in the soil or diluted in the water.

The trees will suck these salts from the ground using their roots and exchange them for sulfur. It adds them to its vegetable marrow and already within its composition, sulfur jumps to the fauna. For this it uses the nutritional transformations of the habitats.

Herbivorous animals, by eating plants, add this chemical to their body. In the same way, carnivorous entities, by eating herbs, whose meat includes sulfur, will acquire this mineral. It is mandatory for its texture and maneuverability.

When these vertebrates die, the corpses are attacked by micro-entities, microbes, and molds. They are broken up and their mass is reduced to organic particles. Since S is part of certain amino acids in the body, soil germs transform it to H sulfide, which, in turn, corrodes and becomes sulfate. Return to the ground and the cycle begins again.

Steps of the sulfur cycle

There are many phases that occur during the transit of sulfur through its cycle:

  • When carnivorous animals perish, the remains are generally detected in the soil. Here they are found by composers who transform the remains of the corpses into salts. It happens as they are dissociated and compressed into organic particles.
  • By existing copiously in the earth’s crust and in the waters as a saline substance; vegetables attract it by its roots. In this way, the flora simplifies the sulfate-salt to sulfides, to carry out its vital performance.
  • Ruminants feed on vegetables that are internally sulfur, transferring them to their bodies.
  • Next, the meat-consuming beasts, by feeding on the herbivores, obtain nutrients and sulfur.
  • When carnivores die, the sulfur located in the acidic amines goes to the earth’s surface. There it is converted into hydrogen sulfide with the help of germs, feeding and improving the soil. It is then digested by the roots of the vegetations, starting the cycle once again.

Also, the decomposition of the excreta of living beings deposited on the earth is a source of sulfur. This has the property of rising to the stratosphere as a gaseous structure of sulfur dioxide and hydrogen sulfide. Likewise, ethers from volcanoes and fires rise. Sulfur dioxide is captivated by vegetations direct from the atmosphere .

Alterations of the sulfur cycle

It is necessary to emphasize that the actions of mortals have been definitive in the alteration of the sulfur circuit . An example of this is the combustion of fossil fuels that releases, in excess, hydrogen sulfide to the environment.

This gas, together with others, when the winter season arrives, promotes the well-known acid rain . It is a caustic precipitation that falls to the ground, transmuting sulfur dioxide into sulfuric acid that ends up damaging marine environments.


Among the derivations are acid showers . They are rains that contain quantities of sulfuric and nitric acid, which they drag from the atmosphere in their fall. These rains undermine nature and lower the pH of aquatic environments, warning of the death of the entities that inhabit them.

They are also harmful to buildings in metropolises because they deteriorate buildings and effigies. One example is the President Lincoln Memorial in Washington DC, which has suffered significant damage over the years from this dangerous rain.


The sulfur cycle is valuable for the support and preservation of life . Its units are a significant fraction of the amino acids that give rise to proteins, glutamate, coenzyme A, thiamine. The same happens with the other basic mixtures of the body.

A large amount of this element contributes so that the proteins retain their shape and perform their tasks properly. At the same time, basic sulfur is highly valued, commercially or industrially.

From it, the well-known sulfuric acid is made, used in factories and at household level. Despite the usefulness, it is pertinent to balance its existence in nature avoiding an exaggerated increase.

Organisms that participate in the sulfur cycle

The bacteria that are the causative entities of the oxidations and contractions of the salt stand out. Because of this, this chemical component can be localized with alum, sulfur or elemental sulfur. Depending on the environment or circumstance, aerobic or anaerobic in which it is found or whether they are deposits on the surface or depression.


There are 3 groups of bacteria that intervene which are listed below:

  • Chemosynthetic bacteria : They resort to the oxidation of H2S to SO4, thus obtaining the energy to produce organic matter.
  • Green and purple photosynthetic bacteria : They oxidize H2S, separating it into hydrogen, H2 and fundamental sulfur, S. Instead of photolysis of H2O, they do anoxygenic photosynthesis , without liberation of oxygen.
  • Anaerobic heterotrophic bacteria: In their respiration, they manipulate sulfates instead of oxygen, as an electron acceptor and compress it to sulfur dioxide, SO2.


The sulfur cycle is important because the realization of this sulfur circuit guarantees that the corresponding activity of proteins and other basic aggregates of the organism occurs in the living being. It means that thanks to him it is possible for living beings to maintain their shape and carry out their work.

On the other hand, S is used in various manufacturing uses. And starting from basic sulfur, sulfuric acid is produced , a substance widely used in industry.

  • In obtaining steel and metal cleaning techniques.
  • The pharmaceutical industry , in treatments against carcinomas
  • To whiten the sugar , in its refining process.
  • In agribusiness , it is treated as a seat for inorganic phosphate fertilizers.
  • In oil refining , as a catalyst in gasoline production factories and others.
  • In water treatment.

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