| The metalloids arsenic (As) and antimony (Sb) are common mining contaminants. Although the geochemical behavior, mobility, and toxicological impacts of As have been studied, Sb is still poorly understood. This study investigates the transformations and biogeochemical cycling of As and Sb in contaminated freshwater environments.;Chapter 1 investigates As and Sb partitioning in a As and Sb contaminated freshwater ecosystem around Stibnite/Yellow Pine Mine, Idaho. Following earlier remediation efforts, stream metalloid concentrations were elevated in reaches immediately downstream of tailings piles, but were within acceptable EPA aquatic life standards. Wetlands surrounding the tailings, however, were highly contaminated. Organisms bioaccumulated both metalloids, with As generally in greater concentrations than Sb. Arsenic showed a decreasing pattern of accumulation with primary producers > tadpoles> sediment > macroinvertebrates > trout > water. Antimony was present in lower concentrations making accumulation trends difficult to discern.;Chapter 2 describes extreme metalloid tolerance in Stibnite Mine wetland tadpoles (Anaxyrus boreas) during development. This study reports the highest whole body As and Sb concentrations ever reported in living tadpoles [As: 3870 mg/kg-1; Sb 315.0 mg/kg-1 (dry wt)], the majority of which was located in the gut as ingested sediment. Metalloid concentration and gut sediment content diminished during tadpole metamorphosis. Biomethylation also contributed to the removal of As from tadpole bodies. High metalloid concentrations did not appear to effect tadpole development rate; however, high Sb- concentrations may affect tadpole size.;Chapter 3 describes a novel strain of Clostridium (designated strain IDSBR-1) isolated from Stibnite Mine wetland sediments that grows by reducing Sb(V) to Sb(III) as a terminal electron acceptor for anaerobic respiration. Bacterial reduction of Sb(V) resulted in the precipitation of antimony trioxide microcrystals that could potentially have commercial applications. This strain also grew using As(V), possibly suggesting a similar metabolic pathway for both metalloids. The significance of geomicrobiological cycling in controlling the environmental redox speciation of As is well established. These results suggest that microbiological processes also mediate the environmental mobility and bioavailability of Sb. |
