Ans. The major reservoirs involved in the sulphur cycle are the biosphere and the atmosphere.In the atmosphere, sulphur is mainly found in the form of sulphur dioxide and hydrogen sulphide. Natural processes as chemical weathering, human activities, and microbial activity are the major sources of sulphur found in the atmosphere. Sulphur in the atmosphere is transported to the biosphere either as fallout or precipitation. At the end of the sulphur cycle, sulphur from the biosphere is transported back into the atmosphere. The biosphere comprises living organisms, of which microorganisms play a very important role in the sulphur cycle. In the biosphere, sulphur is available in organic as well as inorganic forms. The organic form of sulphur travels through the food chain whereas the inorganic form is present in the soil. The biosphere, at times, can also act as a sulphur sink as any living organisms take up sulphur for their growth process and development.