Fixation and mobilization of antimony in sediments

The mobility of sediment antimony (Sb) during sediment-water interactions was studied. Emphasis was placed on the fixation of native and added Sb by sediment, long-term (6 months) releases of Sb and sediment properties that affect the mobilization of Sb.

Sequential selective extraction procedures revealed that most native and added sediment Sb was associated with relatively immobile iron (Fe) and aluminum (Al) compounds. In sediments amended with Sb, concentrations of interstitial water and exchangeable phase Sb were also high. Initial and long-term releases of Sb were much higher from Sb-amended sediments than from sediments containing no added Sb, apparently a result of Sb concentrations in more mobile sediment phases. In most sediments, the largest amount of Sb release occurred early in the leaching experiment. These results suggest that Sb release from contaminated sediments is more likely to occur during the first few months of sediment-water interaction. During aerobic leaching, Sb moved into a more unavailable sediment phase, decreasing the potential for further releases. Sediment Fe and CaCO₃ equivalent concentrations were found to affect releases of added Sb. Evolution of volatile Sb compounds was also noted from sediments under anaerobic conditions.