Abstract: In this study, three representative sulfate minerals (gypsum, anhydrite, and celestite) were co-cultured with a strain
of sulfate-reducing bacteria (SRB). The process of and constraints on anaerobic decomposition of typical sulfate mineral were investigated by monitoring dynamic changes in solution pH, oxidation-reduction potential, protein content, acid-volatile sulfur, and SO₄^2- concentration during the 360-hour incubation period, combined with post-cultivation analysis of mineral surface micromorphology. The results show that oxidation-reduction potential levels follows the order: gypsum system < anhydrite system < celestite system. Concentrations of proteins, SO₄^2-, and acid-volatile sulfur exhibited: gypsum system > anhydrite system > celestite system. SRB growth rates decrease sequentially as: gypsum system > anhydrite system > celestite system. Post-experiment analysis reveals that the formation of etch pits and dissolution micropores on the surfaces of anhydrite and celestite occurs at sites where bacterial cells and their metabolic byproducts made contact. The study demonstrates that anaerobic decomposition process of sulfate mineral is fundamentally constrained by their solubility and dissolution rates. Gypsum with the fastest dissolution rate facilitates robust SRB growth through readily available dissolved SO₄^2-, thereby accelerating its own decomposition. Anhydrite with the moderate dissolution rates supports SRB growth primarily through dissolved SO₄^2- utilization, while bacterial adhesion and metabolic byproducts on mineral surfaces provide additional decomposition enhancement. Celestite possessing both low solubility and slow dissolution rates relies predominantly on bacterial adhesion to promote mineral breakdown, with SRB growth sustained by the limited SO₄^2- released during this gradual decomposition process.

Key words: sulfate mineral, sulfate-reducing bacterium, anaerobic decomposition, dissolution rate, adhesion