The sulfur cycle has both sedimentary and gaseous components. Sulfur enters the biosphere through natural processes like rock weathering and volcanic eruptions or through human activities like burning fossil fuels. It cycles through terrestrial and marine environments and can be found in soil, oceans, plants, and animals. Various bacteria play important roles in processing and transforming sulfur as it moves between the atmosphere, lithosphere, hydrosphere, and biosphere.

1. Sulfur Cycle
Sedimentary and Gaseous

2. • Sedimentary cycle
– Weathering of rock and leaching of its minerals,
transport, deposition and burial.
• Gaseous Cycle
– A biogeochemical cycle with the main reservoir or
pool of nutrients in the atmosphere and ocean

3. Sulfur enters the biosphere through
• Natural Activity
Carried through terrestrial
Weathering of rocks and
environments in salt
decomposition
solution.
Consumers Plants

4. Sulfur enters the atmosphere through
• Natural Activity • Human Activity
Volcanic eruptions, gases Burning of fossil fuels, acidic
released by decomposition drainage from mines
Enters atmosphere as H2S
and reacts with oxygen to
form SO2

5. SO2 is soluble in H2O Acid rain (H2SO4)
consumers plants

6. Death of consumers Sulfur to the atmosphere
Ponds, lakes, seas and soil
oceans

7. Different kinds of bacteria
process this sulfur
Non-photosynthetic photosynthetic
Purple bacteria
Colorless sulfur bacteria
Green bacteria

8. Sulfur
Iron
Ferrous sulfide (FeS2)

9. Sulfur from the oceans
Released in the atmosphere
as Dimethyl sulfide ((CH3)2S )
Go back to the atmosphere
by bacteria fixation, or sea
sprays