Unlike acidic sulfide mine wastes, where metal/loid mobility and bioaccessibility has been widely studied, less attention has been paid to alkaline cyanide heap leaching wastes. Thus, the main goal of this study is to evaluate the mobility and bioaccessibility of metal/loids in Fe-rich (up to 55%) mine wastes resulting from historical cyanide leaching activities. Wastes are mainly composed of oxides/oxyhydroxides (i.e. goethite and hematite), oxyhydroxisulfates (i.e. jarosite), sulfates (i.e., gypsum, evaporitic sulfate salts), carbonates (i.e., calcite, siderite) and quartz, with noticeable concentrations of metal/loids (e.g., 1453–6943 mg/kg of As, 5216–15,672 mg/kg; of Pb, 308–1094 mg/kg of Sb, 181–1174 mg/kg of Cu, or 97–1517 mg/kg of Zn). The wastes displayed a high reactivity upon rainfall contact associated to the dissolution of secondary minerals such as carbonates, gypsum, and other sulfates, exceeding the threshold values for hazardous wastes in some heap levels for Se, Cu, Zn, As, and sulfate leading to potential significant risks for aquatic life. High concentrations of Fe, Pb, and Al were released during the simulation of digestive ingestion of waste particles, with average values of 4825 mg/kg of Fe, 1672 mg/kg of Pb, and 807 mg/kg of Al. Mineralogy may control the mobility and bioaccessibility of metal/loids under rainfall events. However, in the case of the bioaccessible fractions different associations may be observed: i) the dissolution of gypsum, jarosite and hematite would mainly release Fe, As, Pb, Cu, Se, Sb and Tl; ii) the dissolution of an un-identified mineral (e.g., aluminosilicate or Mn oxide) would lead to the release of Ni, Co, Al and Mn and iii) the acid attack of silicate materials and goethite would enhance the bioaccessibility of V and Cr. This study highlights the hazardousness of wastes from cyanide heap leaching, and the need to adopt restoration measures in historical mine sites.This work was supported by the Spanish Ministry of Economic and
Competitiveness through the projects TRAMPA (PID2020–119196RBC21)
and by H2020 European Institute of Innovation and Technology
(EIT RawMaterials) through the project Modular recovery process services
for hydrometallurgy and water treatment (MORECOVERY). This
work was partially supported by FCT (Portugal) through contract UID/
Multi/04349/2019. C.R C´anovas thanks the Spanish Ministry of Science
and Innovation for the Postdoctoral Fellowship granted under application
reference RYC2019–027949-I. M.D. Basallote thanks the Spanish
Ministry of Science and Innovation for the Postdoctoral Fellowship
granted under application reference IJC 2018–035056-I. The authors
would also like to thank to Prof. Edward D. Burton, Ph.D (Editor) and
three anonymous reviewers for the support and comments that notably
improved the quality of the original paper
