SULPHUR CYCLE

1. Reservoirs of sulphur and examples

1.1. INORGANIC RESERVOIRS

1.1.1. Earth Crust

1.1.2. Gypsum

1.1.2.1. Calcium Sulphate

1.1.3. Pyrite (FeS2)

1.1.4. Freshwater (Sulphate, Hydrogen sulfide)

1.1.5. Land (Sulfate)

1.1.6. Atmosphere ( Sulphur Oxide, Methane Sulfonic Acid)

1.1.7. Emission of volcanic fumes

1.1.8. Sediment

1.1.9. Fossil fuels

1.2. ORGANIC RESERVOIRS

1.2.1. Plants

1.2.2. Animals

1.2.3. Bacteria

2. Essential steps in sulphur cycle

2.1. oxidation of sulphite to sulphate

2.1.1. restricted to the bacterial genus Thiobacillus,Thiomicrospira

2.1.2. produce sulphuric acid as metabolic product

2.2. direct reduction of sulphate ions to hydrogen sulphide.

2.2.1. reducing bacteria are heterotrophic that utilixe sulphate,thiosulphate or other reducible sulphur-containing ions as terminal electron acceptors in their respiratory metabolisms.

2.2.2. Lactate is used by the sulphate reducing bacteria during anaerobic respiration to produce acetate.

3. Mineralization of Sulphur

3.1. The breakdown of large organic sulphur compounds to smaller units

3.2. Their conversion into inorganic compounds (sulphates) by the microorganisms.

3.3. Rate of sulphur mineralization is about 1.0 to 10.0 percent/year

3.4. Examples : Hydrogen sulphide , Sulphide mineral