The impact of phlogopite-rich mine tailings on the speciation of water-soluble Pb in contaminated boreal shooting range soil

摘要

Changes in the water-solubility and the speciation of bullet-derived lead (Pb) in a contaminated shooting range soil were investigated in a pot experiment. Samples from the uppermost organic soil were incubated for 21 months with different particle-size fractions of untreated and artificially weathered (i.e. acid-treated) tailings from apatite ore beneficiation. Soil samples were subjected to water extraction. To estimate the proportion of the less toxic, non-cationic and organic Pb compounds in thetotal water-soluble Pb, the extracts were passed through cation exchange columns and analysed for Pb and dissolved organic carbon (DOC) before and after the cation exchange. Addition of untreated tailings to the organic soil decreased the water soluble Pb and increased the relative abundance of water-soluble and non-cationic Pb. On the contrary, incubation with the unsieved or the small particle-size fraction of the acid-treated tailings increased the water-solubility of Pb as well as the relative abundance of the most toxic Pb~(2+) and PbOH~+ species. The results indicated that the untreated and the large-sized acid-treated tailings might be suitable to the remediation of Pb-contaminated soils, whereas the unsieved and the small-sized acid-treated tailings may enhance leaching of Pb and, thus, cannot be considered as amendments.