Effect of Anthropogenic Mercury on Biogeochemical cycle of Gold. Biogeochemical_Gold_Cycle

On Earth's surface to near-surface environment, gold (Au) is progressively transformed through a complex biogeochemical process. On this process, biogeochemical cycling of major, minor biogenic elements and microbiota, especially bacteria play an important role in the transformation of Au by forming biofilm and creating a suitable microenvironment for Au dissolution (i.e., oxidation) and subsequent (re)-precipitation (i.e., reduction) of highly pure, crystalline secondary gold. In the environment the occurrence and behaviour of Au is also strongly intertwined with associated metals i.e., silver, copper and mercury. Environmental hazardous toxic mercury (Hg) has been used for small-scale mining (i.e., Artisanal mining) since roman times and presently using in high quantity in the top gold producing countries such as South Africa, Peru, Mexico and Ghana. This study hypothesize that the prolonged use of toxic Hg on gold mining sites alter the natural biogeochemical cycle of gold. The results of the study explains how continuous use of toxic mercury changes the Au particles morphology, exerts a selective pressure on the microbial community on Au particle and selects heavy metal resistant/transforming bacterial communities in the biofilm. Therefore, the selection of metal resistant biofilm bacterial communities living on gold particle catalyse rapid dissolution and re-precipitation Au and this study estimates that prolonged use of mercury can increase the rate biogeochemical transformation of Au by 5 to 6 times.