Application of sorbents in different soil types from small arms shooting ranges for immobilization of lead (Pb), copper (Cu), zinc (Zn), and antimony (Sb)

Abstract

Soil contamination of ammunition residues at shooting ranges for small arms may be followed by leaching of lead (Pb), copper (Cu), zinc (Zn), and antimony (Sb). Mixing stabilizing agents into the soil may reduce the mobility of the contaminants. To avoid risk of unexpected effects of a stabilizing agent in large-scale measures, the effect of an amendment should be tested on a small scale in advance. Two different amendments, ferric oxyhydroxide powder (CFH-12 from a commercial provider) and zerovalent iron (powder or grit), were mixed into different soil types in order to test their generic effects as stabilizing agents in contaminated soil from shooting ranges. Factors that were considered for their effects were soil water pH, limestone addition, soil chemical composition, and content of organic matter. The stabilizing agents (2–4% weight basis) were mixed into four different soil types contaminated with ammunition residues. The effects of the amendments were elucidated in two column experiments, one small-scale and one larger-scale experiment. Leaching of Pb, Cu, Zn, and Sb from the soil mixed with stabilizing agents was compared with reference soil with no amendments added. Best performance was achieved on leaching of Sb irrespective of the type of iron amendment and soil type. The Sb concentrations in the soil leachates were 55–94% less than in the leachates from the reference soils. Both amendments mixed into an acidic soil reduced the Pb, Cu, and Zn concentrations in the soil leachates in the range of 79–99%. The ability of the amendment to reduce leaching of Pb, Cu, and Zn from the other soil types was highly dependent on soil pH. CFH-12 was acidic and pH had to be balanced with limestone. The general trend was that the iron amendments reduced leaching of the elements in the order Sb>>Cu > Pb ≥ Zn. Iron amendment may be suitable as stabilizing agents for Pb, Cu, Zn, and Sb in soil. The soil pH appeared to be the most important factor governing the mobility of the ammunition residues in the soils. Overall, best effect was achieved with zerovalent iron, which can be purchased at low cost and appeared to have minor influence on the properties of the soils.