This article provides a flow diagram of the sulphur cycle.
Sulfur is one of the essential elements of life system and its major reservoir lies in the earth’s crust together with oceanic sediment. It acts as a component of several compounds like amino acids, protein, enzymes etc. Natural fuel like coal and oils also have some sulfurs (1 to 3%). Burning these materials leads to formation of the gas SO2.
The reactions of this gas with other compounds in the atmosphere are extremely complex, but one of the important products of its solution and further oxidation is sulfuric acid, together with sulfurous acid (both of which occur in combination with rain) forms acid rain.
An overall scheme of global sulphur cycle showing major reservoirs and the flux rates between these are presented in Fig. 5.23. (All values expressed as Tg (g x 1012 or tonnes x 106) sulphur.)
There is a strong analogy between sulfur and nitrogen in the way that micro-organisms influence their biogeochemical cycling. When organic sulfur compounds are decomposed by bacteria, the initial excreted sulfur product is often hydrogen sulfide, H2S.
Many marine phytoplankton’s produce compounds that break down to produce dimethyl sulfide (CH3)2S. Dimethyle sulfide is a major biogenically produced sulfur compound, releasing about 20-40 Tg Sa-1 from the oceans.