Environmental Engineering Reference
In-Depth Information
The natural sulfur cycle is described by the following path:
• Sulfur is naturally released into the atmosphere from rocks and sediment in the forms of hydrogen sulfide
(H
2
S) and sulfur dioxide (SO
2
) through weathering, volcanic eruptions, and the decay of dead organ-
isms.
• Once in the atmosphere, SO
2
reacts with oxygen to form sulfur trioxide (SO
3
) and with water to form
sulfuric acid (H
2
SO
4
).
• Sulfur particles are deposited back into the soil and water, or they combine with water and fall in the form
of acid precipitation.
• Plants absorb sulfate ions (SO
4
2-
) through their roots, and animals receive sulfur by consuming plants.
Humans have also affected the sulfur cycle through industrial processes and coal burning, from which sulfur is
emitted into the atmosphere in the forms of SO
2
and H
2
SO
4
.
In each biogeochemical cycle, matter is being cycled throughout ecosystems. This movement of nutrients
throughout various parts of an ecosystem—both biotic and abiotic—exemplifies the conservation of matter,
which states that matter cannot be created or destroyed.
