Overview:

Calcium Sulfate (CaSO₄) more commonly known as gypsum is a naturally occurring white crystalline mineral that has many different uses and applications. Gypsum in its hydrated form (CaSO₄•2H₂O) is used in the construction industry for fire resistance in buildings. Outside of the construction industry, gypsum is used in the food and fertilizer industry for calcium and sulfate fortification respectively. When gypsum is no longer usable, it is deposited in construction and demolition(C&D) landfills where anaerobic (low oxygen) conditions and the presence of sulfate-reducing bacteria promote the decomposition of wallboard/gypsum into hydrogen sulfide gas (H₂S). Due to local and state regulations on odor control, these C&D sites monitor their fill for hydrogen sulfide gas.  This paper will couple two methods of analysis to observe the relationship between the purity of gypsum (calcium sulfate dihydrate) and hydrogen sulfide concentration as a sample is fermented by sulfate-reducing agents (e.g. bacteria). The scope of this research may be beneficial for industrial hygienists concerned with C&D landfill H₂S levels or for incoming gypsum processing plants who suspect poor quality gypsum.