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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.

A multidisciplinar analysis of sediments collected in different environments of the Doñana National Park (Guadalquivir estuary, SW Spain) provides an overview of the textural, mineralogical and physico-chemical parameters that control the distribution of benthic foraminifera in this Biosphere Reserve. These microorganisms are absent in the fine quartzitic sands that constitute the substrate of temporary ponds with brief hydroperiods located in the dune systems and spits, as well as in other ponds with low conductivities or hypersaline conditions located in the inner marshland or near the Guadalquivir river banks. Benthic foraminifera are mainly found on phyllosilicate-rich, silty-clayey substrates, where cluster analysis permits to delimitate six foraminiferal assemblages. Cluster II (Ammonia inflata + Haynesina germanica) is the dominant assemblage in the central ponds and the margins of the main channels, while cluster IV (Trochammina inflata + Entzia macrescens) is restricted to some ponds located on the high marsh and cluster VI (Ammonia beccarii + Quinqueloculina spp.) is abundant on external beaches. Tidal fluxes cause the transport of marine species both to the inner areas of the estuary and to these beaches.

Numerous investigations have used the foraminiferal assemblages or species as bioindicators. This paper tests the responses of these microorganisms to different environmental changes (heavy metal pollution, treatment stations, artificial inlets, agricultural and urban sewages) and compares them to those observed previously on ostracod assemblages. Foraminifera are more tolerant to these changes, while ostracods present a more specialized response. Numerous investigations have used the foraminiferal assemblages or species as bioindicators. This paper tests the responses of these microorganisms to different environmental changes (heavy metal pollution, treatment stations, artificial inlets, agricultural and urban sewages) and compares them to those observed previously on ostracod assemblages. Foraminifera are more tolerant to these changes, while ostracods present a more specialized response.

Numerous investigations have used the foraminiferal assemblages or species as bioindicators. This paper tests the responses of these microorganisms to different environmental changes (heavy metal pollution, treatment stations, artificial inlets, agricultural and urban sewages) and compares them to those observed previously on ostracod assemblages. Foraminifera are more tolerant to these changes, while ostracods present a more specialized response., Numerosas investigaciones han utilizado a las asociaciones o especies de foraminíferos como bioindicadores. Este trabajo investiga la respuesta de estos microorganismos ante diferentes cambios ambientales (contaminación por metales pesados, estaciones de tratamiento de residuos, pasajes artificiales, desechos urbanos e industriales) y la compara con la observada previamente en las asociaciones de ostrácodos. Los foraminíferos son más tolerantes a estos cambios, en tanto que la respuesta de los ostrácodos es más especializada.