Browsing by Subject "soil contamination"

Antimony (Sb) is an element that is used widely for industrial purposes, for example, as a hardening agent in lead (Pb) ammunition. In soil, antimony typically occurs as antimonous acid Sb(OH)3 in anaerobic conditions and as antimonate Sb(OH)6- in aerobic conditions. Antimony mobility is controlled by sorption to oxide surfaces in soil and low pH favors the adsorption. Antimony contamination in shooting range soil can pose a risk for human health and ecosystems. In shooting range soil, antimony co-occurs with lead that is typically found in cationic Pb2+ form. Different adsorption behaviour of cationic Pb2+ and anionic Sb(OH)6- renders remediation of contaminated shooting range soil challenging, since amendments designed for lead stabilization can increase solubility of antimony. The aim of this study was to reveal how apatite ore mine tailings-treatment of antimony-contaminated soil affects antimony solubility in soil and if it has potential for immobilizing antimony in shooting range soil. The hypothesis of the research was that mine tailings treatment decreases the mobility of antimony in soil due to reactions of between antimony and components of the mine tailings material. In laboratory, soil samples from O horizon, B horizon, and C horizon of a former shooting range area in Svärdfelt, Sipoo were incubated for 2.5 years with and without tailings. Tailings-induced changes in the distribution of antimony between various chemical pools in soil were investigated with a sequential extraction method. Soil pH, electrical conductivity, oxalate-extractable Al, Fe and Mn concentrations, and calcium Ca2+ concentrations, as well as tailings-induced changes in the distribution of phosphorus P between chemical pools, were also determined. Contrary to the hypothesis, the increase in pH and phosphorus concentration induced by the tailings treatment can decrease the adsorption of antimony to oxide surfaces and, thus, increase its solubility. Results of the study indicate that the mine tailings treatment decreases total extractability of antimony possibly through formation of poorly soluble calcium antimonates. No significant increase in potentially bioavailable (soluble and labile) antimony fractions was observed, either. These results indicate that mine tailings material has the potential to act as an amendment in in situ remediation of shooting range soil.