How do the occurrence patterns of potentially toxic elements (PTEs) control their release behaviours from Pb/Zn smelter contaminated soils?

Abstract

Little information is available on the occurrence patterns of potentially toxic elements (PTEs) controlling their release behaviors, according to the results from leaching tests, multidisciplinary characterization and geochemical modeling. In this study, the occurrence characteristics of PTEs were dentified by combining Tessier results with X-ray photoelectron spectroscopy (XPS) and mineral liberation analyzer (MLA) and their main release mechanisms were elucidated based on geochemical modeling results from PHREEQC software. The results indicated that 0–17.69% of As, 0–27.90% of Pb and 0–82.17% of Zn were hosted in the non–reactive silicate minerals, respectively, while 82.31–100 % of As, 0–100 % of Pb and 17.82–100% of Zn were hosted in the reactive minerals, respectively. Among these studied metals, 45.78–81.73% of Cd was mainly associated with the labile fractions. PTEs presented highly pH and acidity–dependent leaching characteristics. Acidification prediction results indicated that soil pH could decrease to a value of 6 within a wide time range of 15–388 years. PTEs release were mainly controlled by the dissolution of metal–rich oxide and carbonate mineral phases, as well as the adsorption/desorption and co–precipitation/dissolution of Fe, Mn and Al bearing oxyhydroxide minerals and the complexation of dissolved organic matter (DOM). These findings would extend the knowledge to the scenario based leaching assessment studies of smelter contaminated soils.