Pyrites (FeS2) were widespread and important minerals, mainly used in the manufacture of sulfuric acid, and were heavily mined in the last few decades globally which generated huge numbers of pyrite tailings. In many developing countries and low income areas, pyrite tailings were discarded in the valley near the pyrite mine without further reasonable disposal as the reuse value of pyrite tailings was low. The FeS2 in pyrite tailings can be oxidized to soluble iron (Fe2+ and Fe3+), sulfate, and hydrogen ion (H+), present in the leachate, with the participation of oxygen, water, and certain microbes when the pyrite tailings are directly exposed to the air (Lowson, 1982; Edwards et al., 1998). Therefore, the pyrite tailings leachate, one kind of acid mine drainage (AMD), has strong acidity and contains high concentration of iron (Fe), sulfate (SO42−), and other heavy metals which can cause serious pollution to the downstream water (Li et al., 2019). The ecological system of the river polluted by pyrite is usually seriously destroyed by low pH, high heavy metal concentration, and high turbidity caused by hydrolysis of iron ion (Liu et al., 2015). To better understand the pollutant generating process and further reduce the production of pollution, plenty of research had revealed the special bacteria such as Thiobacillus, Leptospirillum, Sulfobacillus, and Thiomonas which could fasten the pyrite oxidization (Crundwell, 1996; Edwards et al., 1998; Yahya and Johnson, 2002; Han et al., 2013). However, the holistic bacterial communities in pyrite tailings polluted areas and the modification of the downstream bacterial communities by pyrite tailings are still not clear which further impede the cognition of the potential effect of pyrite tailings pollution.
To increase pH and precipitate iron ion, alkali neutralization process was used to AMD treatment and gradually became a common method (Santomartino and Webb, 2007; Park et al., 2019). With the development of treatment technology, sodium hydroxide (NaOH) or calcium hydroxide (Ca(OH)2) coupled with polyacrylamide (PAM) was recognized as the rapid and effective approach to treating pyrite tailings leachate. However, this method consumed large amounts of potions and further increased the cost of pollutant control. The generation of leachate in pyrite tailing ponds or heaps usually continues for decades and alkali neutralization process will cause large amounts of cost. More importantly, a great deal of sludge generated from neutralization process needs further treatment and management which are high priced (Naidu et al., 2019). The government or relevant company will be difficult to cover the cost of potions for decades which need to develop a series of new technologies based on microbial or ecology methods to reduce the overall treatment cost partial like the municipal or industrial wastewater treatment process. In recent years, many biological remediation methods such as bio-reactors, permeable reactive barriers, and wetlands had been established mainly utilized the sulfate reducing bacteria (SRB) to remove sulfate and heavy metals (Giordani et al., 2019; Rambabu et al., 2020; Singh and Chakraborty, 2020). However, the limitation of existing biological technology is the dependence on carbon sources and hard adaptation to high pollutant concentrations which is very common in contaminated sites, since the characteristics of SRB (Rambabu et al., 2020; Zhang et al., 2021). Therefore, the bacterial communities and their interaction of real pyrite tailings leachate and its pollutant areas need to be deeply researched to find more adaptable bacteria in future and provide the fundamental theories of bio-ecology pyrite tailings leachate treatment process.
To explore the bacterial communities in the polluted area of pyrite tailings, an actual river flowing through the pyrite tailings polluted areas was selected and the bacteria in the water and sediment of upstream, pollutant source, and downstream were analyzed by Illumina Hiseq sequencing in this study. The findings innovatively revealed the bacterial communities of pyrite tailings polluted area and further confirmed the effect of pyrite tailings pollution on natural water bodies.