An assessment of the environmental fate of mercury species in highly polluted brownfields by means of thermal desorption

High contents of mercury (Hg) have been found in old mining-metallurgy sites occurring a widespread contamination and degradation of the land. The ability to identify the Hg species present in these areas is essential to clarify fate of Hg and its bioavailability and additionally, to be able to parameterize remediation techniques based on thermal desorption in order to carry out a full-scale decontamination of the land. This study has proven the usefulness of a thermal programmed desorption procedure (Hg-TPD) for identifying Hg species in contaminated samples related to mining-metallurgy activities. Hg bound to organic matter (Hg-OM) and to pyrite (Hg-FeS2), HgS red, HgCl2, Hg and HgO were identified in most of waste samples. The absence of mobile Hg species in soils and sediments showed both its re-emission to the atmosphere (Hg) or of its oxidation and lixiviation (HgO and HgCl2) over the years. The results have demonstrated that most of these polluted solids can be remediated by thermal treatment at temperatures ranging between 150 and 600 degrees C. The study evidence that Hg-TPD is useful either for parameterizing a thermal remediation or for identifying the evolution pathways of Hg species in different environmental compartments and in general, for any environmental remediation treatment. (C) 2016 Elsevier B.V. All rights reserved.