Antimony leaching from contaminated soil under manganese- and iron-reducing conditions: column experiments

Abstract

Environmental context Contamination of shooting range soils by antimony (Sb) released from corroding ammunition has become an issue of public environmental concern. Because many of these sites are subject to waterlogging and consequently limited aeration, we performed column experiments with contaminated shooting range soil to investigate Sb mobility under such conditions. The results are important for our understanding of the risks arising from Sb-contaminated soils, and also for the derivation of appropriate management strategies for such sites. Abstract Despite the environmental risks arising from antimony-contaminated sites, critical factors controlling the mobility of Sb in soils have still not been fully identified to date. We performed column experiments to investigate how reducing conditions affect Sb leaching from a calcareous shooting range soil, with a special focus on the relationship between Sb release and mineral dissolution processes. After eluting the columns for 5 days with 15mM lactate solution at a flow rate of 33mm day–1, the flow was interrupted for 37 days and then resumed for another 5 days. With the transition to moderately reducing conditions (~300mV) after 1 day of flow, effluent SbV and manganese (Mn) concentrations showed a concomitant increase, providing evidence that SbV associated to these phases was released by the reductive dissolution of Mn minerals. The release of SbV was counteracted by the reduction to SbIII, which was first scavenged by iron (Fe) (hydr)oxides and then slowly liberated again when the redox potential further decreased to Fe-reducing conditions. Laser ablation–inductively coupled plasma–mass spectrometry revealed the presence of an initial pool of Sb associated with Mn-containing, Fe-free phases, underpinning the important role of the latter in addition to Fe (hydr)oxides as Sb sorbents.