The Sulfur CycleBY SOPHIA VELIS & CHEN WU

Natural Process

The way it works Most sulfur is stored in ocean sediments and underground

in rocks and minerals in the form of sulfate (SO42-)

It enters the atmosphere as hydrogen sulfide (H2S) through highly active volcanoes and decomposing organic matter by anaerobic decomposers normally found in flooded swamps, bogs, and tidal flats. Sulfur dioxide (SO2) is also released from volcanoes.

Sea spray, dust storms, and forest fires release sulfate salts into the atmosphere. Plants absorb the sulfates and incorporate them as an essential component of many proteins.

The way it works

Certain kinds of marine algae produce large amounts of volatile dimethyl sulfide or DMS (CH3SCH3). While in the atmosphere DMS is turned into sulfur trioxide gas (SO3) and to tiny droplets of sulfuric acid (H2SO4) which fall down to earth as acid rain.

In the oxygen-deficient environments like flooded soils, freshwater wetlands, and tidal flats, specialized bacteria convert sulfate ions to sulfide ions (S2-). The sulfide ions can then react with metal ions to form insoluble metallic sulfides, which are deposited as rock or metal ores, and the cycle continues.

Natural reservoirs The atmosphere In animals In plants Ocean

sediments Soil Rock Fossils fuels

Why is it important?

The sulfur cycle is important because it helps with functioning of enzymes and protein for plants and animals that depend on plants.

Human Impact Humans impact this cycle by releasing to much sulfur

into the atmosphere. It interrupts the cycle. MDCs like the US and Japan greatly impact it because of their large oil industries. The burning of fossil fuels increases the rate at which sulfur is entering the atmosphere greatly, and that prevents the sulfur from going back into the soil and the biosphere and it also results in acid rain. LDCs such as Venezuela or India also contribute to the interruption of the sulfur cycle.

Human Impacts (continued) In India, because of their

worship of cows, they don't kill them and therefore, there is a surplus of cows. Because cows are herbivores, they eat lots of grass, and that grass contains sulfur. Which is released in the form of flatulence, which they do very often.

Pathway affected by human activities

The natural state of sulfur is normally found in rocks, ocean sediments, and in metals. They can be released naturally into the atmosphere through volcanoes and algae. But humans mine for fossil fuels that contain sulfur in them. The extraction of sulfur in the soil and rocks takes away from the plants that obtain sulfur from the soil. Humans also burn the fossil fuels that contain sulfur, and increase the rate in which sulfur enters the atmosphere. In natural circumstances, sulfur returns to the ground in the form acid rain that is basic enough to be safe to organisms. But because of the increased amount of sulfur in the atmosphere, the acid rain is too acidic and can damage the biosphere.