The Transformation of Hg(2+) during Anaerobic S(0) Reduction by an AMD Environmental Enrichment Culture

Mercury (Hg) is a highly toxic and persistent heavy metal pollutant. The acid mine drainage (AMD) environment in sulfide-mining areas is a typical Hg pollution source. In this paper, the transformation of Hg(2+) during anaerobic S(0) reduction by an AMD environmental enrichment culture was studied by multiple spectroscopic and microscopic techniques. The experimental results showed that the microbial S(0) reduction of the AMD enrichment culture was significantly inhibited in the presence of Hg(2+). The results of cell surface morphology and composition analysis showed that there was obvious aggregation of flocculent particles on the cell surface in the presence of Hg(2+), and the components of extracellular polymeric substances on the cell surface changed significantly. The results of surface morphology and C/S/Hg speciation transformation analyses of the solid particulate showed that Hg(2+) gradually transformed to mercuric sulfide and Hg(0) under anaerobic S(0) reduction by the AMD enrichment culture. The microbial community structure results showed that Hg(2+) significantly changed the enrichment community structure by decreasing their evenness. The dominant microorganisms with S(0) reduction functions are closely related to mercury transformation and are the key driving force for the transformation of substrate solid particulate and cellular substances, as well as the fixation of Hg(2+).