Biogeochemical processes governing natural pyrite oxidation and release of acid metalliferous drainage

The oxidative dissolution of sulfide minerals (principally pyrite) is responsible for the majority of acid metalliferous drainage from mine sites, which represents a significant environmental problem worldwide. Understanding the complex biogeochemical processes governing the natural pyrite oxidation is critical to not only solving this problem but also industrial bioleaching of sulfide minerals. To this end, we conducted a simulated experiment of natural pyrite oxidative dissolution. Microbial community analysis assessed by pyrosequencing revealed a distinct succession across the three stages: at the early stage, a newly proposed genus Tumebacillus using sodium thiosulfate and sulfite as sole electron donors, dominated the microbial community; at the mid stage, Alicyclobacillus (the fifth most abundant genus at the early stage) became the most dominant genus, while Tumebacillus was still ranked as the second most abundant genus; at the last stage, the microbial community was dominated by Ferroplasma (the tenth most abundant genus at the early stage). The geochemical and mineralogical analyses showed that the exchangeable heavy metals increased as the oxidation progressed and that some secondly sulfate minerals (including jarosite and magnesiocopiapite) were formed at the last stage of the oxidation. Moreover, we proposed a comprehensive model of biogeochemical processes governing oxidation of sulfide minerals.