Antimony (Sb) Contaminated Shooting Range Soil: Sb Mobility and Immobilization by Soil Amendments

Antimony (Sb) in lead bullets poses a major environmental risk in shooting range soils. Here we studied the effect of iron (Fe)-based amendments on the mobility of Sb in contaminated soil from shooting ranges in Norway. Untreated soil showed high Sb concentrations in water extracts from batch tests (0.22-1.59 mg L-1) and soil leachate from column tests (0.3-0.7 mg L-1), occurring exclusively as Sb(V). Sorption of Sb to different iron-based sorbents was well described by the Freundlich equation (Fe-2(SO4)(3), log K-F = 6.35, n = 1.51; CFH-12 (Fe oxyhydroxide), log K-F = 4.16-4.32, n = 0.75-0.76); Fe-0 grit, log K-F = 3.26, n = 0.47). These sorbents mixed with soil (0.5 and 2% w/w), showed significant sorption of Sb in batch tests (46-92%). However, for Fe-2(SO4)(3) and CFH-12 liming was also necessary to prevent mobilization of lead, copper, and zinc. Column tests showed significant significant retention of Sb (89-98%) in soil amended with CFH-12 (2%) mixed with limestone (1%) compared to unamended soil. The sorption capacity of soils amended with Fe-0 (2%) increased steadily up to 72% over the duration period of the column test (64 days), most likely due to the gradual oxidation of Fe-0 to Fe oxyhydroxides. Based on the experimental results, CFH-12 and oxidized Fe-0 are effective amendments for the stabilization of Sb in shooting range soils.