Microbial Activities Response to Contamination in Soil and Sediments Rich in As Surrounding an Industrial Gold Mine

Gold mines are widely recognized as important sources of arsenic (As) pollution and this work proposes the use of in situ microbial community enzymatic response to assess the risk of As in soil and sediments surrounding “Morro do Ouro,” the largest industrial gold mine in Brazil. Bacterial community exposed to high metals concentrations deviates energy from growth to cell maintenance modifying enzymatic activity response. Even if the number of bacterial cells presented in soil and sediment samples was in the same order of 10 7 cell cm −3 , it declines in sediment samples closer to a mining area. Dehydrogenase activity (DHA) showed the same trend, suggesting inhibition by toxic effect of metals, while esterase activities (EST) behaved in the opposite way, representative of increasing energy demand by the community under environmental stress. The Quality Ratio (QR) index for environmental risk assessment was applied to integrate geochemical (grain size, total organic carbon contents, and metals as indicators of complex contamination) and microbial parameters (DHA—energy production into cell and EST—hydrolase organic matter outside the cell membrane). QR indicated that the risk associated with soil and sediment is driven by As levels and decreases from the mine facilities.