Microbial processes and arsenic mobilization in mine tailings and shallow aquifers

Microbial processes play an important role in transforming and mobilizing As in the sub-surface. Enrichment cultures indicated several As tolerant species, which actively reduced As(V) to As(III). No change in As speciation occurred in the controls, thereby confirming As(V) reduction was biologically mediated, and active metabolism was a prerequisite for reduction. Different growth and As(V) reduction rates were noted under oxic to sub-oxic conditions, and a zero-order model best fits the As(V) reduction data. Arsenic concentrations in the microcosms seem to affect biomass yield and As(V) reduction rates in some of the strains. Arsenic reduction in these microorganisms probably occurs for respiratory or detoxification purposes. It is likely that microbial mobilization of As may have an impact on groundwater remediation treatment in these environments.