1. STEPS
1.1. OXIDATION
1.1.1. By the bacterial genus Thiobacillus, genus Thiomicrospira & genus Sulfolobus
1.1.1.1. Oxidation of sulphur or sulphides to produce energy and sulphuric acid as a metabolic product
1.1.2. By bacteria, Thiobacillus ferrooxidans (act as catalyst)
1.1.2.1. Oxidation of iron sulphur minerals pyrite and pyrrhotite to produce Acid Rock Drainage (ARD)
1.2. REDUCTION
1.2.1. By sulphate reducing bacteria (SRB)
1.2.1.1. SRB utilise sulphate, thiosulphide or other reducible sulphur- containing ions as terminal electron acceptor in their respiratory metabolism
1.2.1.1.1. sulphur containing ions are reduced to hydrogen sulphide
1.3. MINERALIZATION
1.3.1. By plants
1.3.1.1. sulphur -> sulphydryl form
1.3.2. by soil
1.3.2.1. sulphur is mineralised, portion of inorganic sulphur is released and utilised by microflora for cell synthesis and remainder is released into the environment
2. RESERVOIR
2.1. EARTH'S CRUST
2.1.1. GYPSUM
2.1.2. PYRITE
2.2. OCEAN
2.2.1. SULFATE ANION
2.3. FRESH WATER
2.3.1. HYDROGEN SULFIDE
2.3.2. SULFATE
2.3.3. ELEMENTAL SULFUR
2.4. LAND
2.4.1. SULFATE
2.5. ATMOSPHERE
2.5.1. SULFUR OXIDE
2.5.2. METHANE SULFONIC ACID