Microbial Drivers Of Sulfate Formation And Evolution In Mine Water

Sulphate mine water is one of the important types of coal mine water in China.Microorganisms play an important role in the formation of high-sulfate mine water,which seriously endangers the health of the ecosystem.This thesis first investigated the distribution characteristics of microbial communities in mine water with different sulphate concentrations.Then,through indoor simulation experiments,studies the change characteristics of mine water under the action of water-rock-microbial three fields under temperature and redox conditions.Finally,the effect of microorganisms on high sulphate concentrations is discussed.Mechanism of action for mine water formation.The main conclusions are:（1）The sulphate concentration in coal mine water ranges from 90.25 mg/L to5065.95 mg/L.There were significant differences in the composition of microbial communities in mine waters with different sulphate concentrations.When the SO₄^2-concentration was 250-1000 mg/L,the abundance and diversity of the bacterial community were higher,the sulfur cycle bacteria and sulfur cycle genes were lower,and the microorganisms involved in the sulfur cycle were not active.When the concentration of SO₄^2-exceeded 1000 mg/L,the abundance and diversity of bacteria decreased with increasing concentration.The dominant bacterial phylum in the mine water was Proteobacteria.When the SO₄^2-concentration was lower than 250 mg/L or higher than 1000 mg/L,the water had abundant sulfur cycle related bacteria and sulfur cycle genes.（2）The simulation test of the water-rock-microbial reaction under temperature conditions showed that the SO₄^2-concentration after 28 days of reaction was 6.85%higher at 35°C than at 25°C.There was no significant difference in the diversity of the bacterial community between the two incubation temperatures.Thiobacillus increased by 14.74%when cultured at 35°C compared to 25°C.In addition,functional genes involved in sulfur oxidation,such as sulfur oxidation,sulfur compound oxidation and thiosulphate oxidation,were significantly higher at 35℃than at 25℃.The higher temperature under open conditions promoted a number of sulfur oxidations by sulfur oxidising bacteria in the system.（3）The simulation test of water-rock-microbial reaction under redox conditions showed that under open oxidation conditions,the pH and SO₄^2-concentration in water increased,while under closed anaerobic conditions,both pH and SO₄^2-concentration in water decreased.The richness of the bacterial community in the closed culture system was significantly higher than that in the open culture system,and there was no significant difference in the diversity of the bacterial community.The sulfur oxidising bacteria in the open system promoted the formation of sulphate in the system through the oxidation of sulfur compounds and the oxidation of thiosulphate.The sulphate and sulphite reducing bacteria and fermenting bacteria in the closed system reduced the pH and SO₄^2-concentration in the system through fermentation,sulphate reduction and sulphite reduction.These functional genes were significantly different between the two reaction systems.（4）During open culture,the concentration of SO₄^2-increased by 11.91%driven by microbial action.When sterile participated in the reaction,the concentration of SO₄^2-driven by the redox potential increased by 3.91%（open）and 5.49%（closed）,respectively.The driving effect of microbial action is stronger than that of redox potential.The research results provide a theoretical reference for the distribution characteristics of microbial communities in different concentrations of sulphate mine waters and the formation mechanism of high sulphate mine waters in coal mines.