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In May 2017, a spill from La Zarza pit lake (SW Spain) resulted in the release of approximately 270,000 m 3 of extremely acidic waters to the Odiel River. Around 780 × 10 3  kg of Fe, 170 × 10 3  kg of Al, 2.15 × 10 3  kg of As and high amounts of other trace metals and metalloids were spilled. The purpose of this study is to explain the causes, consequences and impacts of the mine spill on the receiving water bodies. To this end, an extensive sampling along the mine site, river and estuary as well as a hydrological model of the pit lake was performed. Around 53 km of the Odiel River's main course, which was already contaminated by acid mine drainage (AMD), were affected. The mine spill resulted in an incremental impact on the Odiel River water quality. Thus, dissolved concentrations of some elements increased in the river up to 450 times; e.g. 435 mg/L of Fe and 0.41 mg/L of As. Due to low pH values (around 2.5), most metals (e.g., Cu, Zn, Mn, Cd) were transported in the dissolved phase to the estuary, exhibiting a conservative behavior and decreasing their concentration only due to dilution. However, dissolved concentrations of Fe, Cr, Pb, Se, Sb, Ti, V and especially As decreased significantly along the river due to Fe precipitation and sorption/coprecipitation processes. At the upper zone of the estuary, a noticeable increment of metal concentrations (up to 77 times) was also recorded. The water balance illustrates the existence of groundwater inputs (at least 16% of total) to the pit lake, due probably to local infiltration of rainwater at the mining zone. The probable existence of an ancient adit connected to the pit lake indicates that potential releases could occur again if adequate prevention measures are not adopted., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Carbon-capture and storage is considered to be a potential mitigation option for climate change. However, accidental leaks of CO 2 can occur, resulting in changes in ocean chemistry such as acidification and metal mobilization. Laboratory experiments were performed to provide data on the effects of CO 2 -related acidification on the chemical fractionation of metal(loid)s in marine-contaminated sediments using sequential extraction procedures. The results showed that sediments from Huelva estuary registered concentrations of arsenic, copper, lead, and zinc that surpass the probable biological effect level established by international protocols. Zinc had the greatest proportion in the most mobile fraction of the sediment. Metals in this fraction represent an environmental risk because they are weakly bound to sediment, and therefore more likely to migrate to the water column. Indeed, the concentration of this metal was lower in the most acidified scenarios when compared to control pH, indicating probable zinc mobilization from the sediment to the seawater., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This study aims to explore the impact of chronic metal exposure derived from persistent pollution from mining activity using human gallstones as proxies. The samples were obtained from patients residing in geologically and environmentally contrasting areas in the Province of Huelva, SW Spain, allowing for the evaluation of the regional effect of metal pollution. The study group resides in the Iberian Pyrite Belt characterized by natural and anthropogenic metal pollution from mining activities, whereas the control group resides in the Ossa Morena Zone famous for its natural parks. A total of 68 gallstones were first classified based on their phase composition and structure and subsequently their chemical composition was studied using solution Inductively Coupled Plasma-Mass Spectrometry. The metal concentrations increased in the cholesterol-rich gallstones from pure, to mixed and composite cholesterol stones along with the increasing amount of minor phases, such as bilirubinate, carbonate, and phosphate. These cholesterol stones did not show an evident enrichment tendency. On the contrary, pigment stones, composed of bilirubinate, carbonate, and phosphate phases, were rich in a variety of elements and the regional comparison showed that the pigment stones from the study area were enriched in sulfide-associated metal(loid)s, Mn, Fe, Cu, Zn, Sr, As, Ag, Sb, and Pb with respect to the control group. Inhalation of polluted airborne particulate matter is considered as one of the main exposure routes among the residents of the study area. Additionally, consumption of local water and locally produced food products such as fruit and vegetables and dermal contact may be possible sources of exposure, but no direct connection was observed., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Streams and rivers strongly affected by acid mine drainage (AMD) have legal vacuum in terms of assessing the water toxicity, since the use of conventional environmental quality biomarkers is not possible due to the absence of macroinvertebrate organisms. The Asian clam Corbicula fluminea has been widely used as a biomonitor of metal contamination by AMD in freshwater systems. However, these clams are considered an invasive species in Spain and the transplantation in the field study is not allowed by the Environmental Protection Agency. To evaluate the use of the freshwater bivalve C. fluminea as a potential biomonitor for sediments contaminated by AMD, the metal bioavailability and toxicity were investigated in laboratory by exposure of clams to polluted sediments for 14 days. The studied sediments were classified as slightly contaminated with As, Cr, and Ni; moderately contaminated with Co; considerably contaminated with Pb; and heavily contaminated with Cd, Zn, and specially Cu, being reported as very toxic to Microtox. On the fourth day of the exposure, the clams exhibited an increase in concentration of Ga, Ba, Sb, and Bi (more than 100 %), followed by Co, Ni, and Pb (more than 60 %). After the fourth day, a decrease in concentration was observed for almost all metals studied except Ni. An allometric function was used to determine the relationship between the increases in metal concentration in soft tissue and the increasing bioavailable metal concentrations in sediments.

The Iberian Pyrite Belt (SW Iberian Peninsula) has intense mining activity. Currently, its fluvial networks receive extremely acid lixiviate residue discharges that are rich in sulphates and metals in solution (acid mine drainage, AMD) from abandoned mines. In the current study, the sediment and water quality were analysed in three different areas of the Odiel River to assess the risk associated with the metal content and its speciation and bioavailability. Furthermore, sediment contact bioassays were performed using the freshwater clam Corbicula fluminea to determine its adequacy as a biomonitoring tool in relation to theoretical risk indexes and regulatory thresholds. Reburial activity and mortality were used as the toxic responses of clams when exposed to contaminated sediment. The results showed coherence between the water and sediment chemical contamination for most of the metals. The reburial activity was correlated with the metal toxicity, but no clam mortality was registered. The bioaccumulation of the studied metals in the clam did not have a significant correlation with the bioavailable fraction of the metal content in the environment, which could be related to a potential different speciation in this singular environment. The bioaccumulation responses were negative for As, Cd and Zn in highly contaminated environments and were characterized as severe, considerable and low potential environmental risks, respectively. The results show that C. fluminea is a good biomonitor of Cu and Pb., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Acid mine drainage in the Iberian Pyrite Belt is probably the worst case in the world of surface water pollution associated with mining of sulphide mineral deposits. The Iberian Pyrite Belt is located in SW Iberian Peninsula, and it has been mined during the last 4,500 years. The central and eastern part of the Iberian Pyrite Belt is drained by the Tinto and Odiel rivers, which receive most of the acidic leachates from the mining areas. As a result, the main channels of the Tinto and Odiel rivers are very rich in metals and highly acidic until reaching the Atlantic Ocean. A significant amount of the pollutant load transported by these two rivers is delivered during the rainy season, as is usual in rivers of Mediterranean climate regions. Therefore, in order to have an accurate estimation of the pollutant loads transported by the Tinto and Odiel rivers, a systematic sampling on a weekly basis and a high temporal resolution sampling of floods events were both performed. Results obtained show that metal fluxes are strongly dependent on the study period, highlighting the importance of inter-annual studies involving dry and wet years.

The Iberian Pyrite Belt (IPB), SW Spain and Portugal, contains about 100 abandoned mine wastes and galleries that release acid mine drainages (AMD) to the Tinto and Odiel rivers. In situ passive remediation technologies are especially suitable to remediate the drainages of these orphan sites. However, traditional remediation systems, designed for coal mines, have been demonstrated inefficient to treat the IPB mine waters. Due to their high acidity and metal loads, large amount of solids precipitate and fast clogging of porosity or passivation (coating) of the reactive grains occurs. To overcome these problems, the dispersed alkaline substrate (DAS) a mixture of fine-grained limestone sand and a coarse inert matrix (e.g., wood shavings) was developed. The small grains provide a large reactive surface and dissolve almost completely before the growing layer of precipitates passivates the substrate. The high porosity retards clogging. However, calcite dissolution only raises pH to values around 6.5, at which the hydroxides of trivalent metals (Al and Fe) precipitate, but it is not high enough to remove divalent metals. Caustic magnesia (MgO) buffers the solution pH between 8.5 and 10. A DAS system replacing limestone with caustic magnesia has been tested to be very efficient to remove divalent metals (Zn, Cd, Mn, Cu, Co, Ni, and Pb) from the water previously treated with calcite.

As acid mine drainage (AMD) remediation is increasingly faced by governments and mining industries worldwide, the generation of metal-rich solid residues from the treatments plants is concomitantly raising. A proper environmental management of these metal-rich wastes requires a detailed characterization of the metal mobility as well as an assessment of this new residues stability. The European standard leaching test EN 12457-2, the US EPA TCLP test and the BCR sequential extraction procedure were selected to address the environmental assessment of dispersed alkaline substrate (DAS) residues generated in AMD passive treatment systems. Significant discrepancies were observed in the hazardousness classification of the residues according to the TCLP or EN 12457-2 test. Furthermore, the absence of some important metals (like Fe or Al) in the regulatory limits employed in both leaching tests severely restricts their applicability for metal-rich wastes. The results obtained in the BCR sequential extraction suggest an important influence of the landfill environmental conditions on the metals released from the wastes. To ensure a complete stability of the pollutants in the studied DAS-wastes the contact with water or any other leaching solutions must be avoided and a dry environment needs to be provided in the landfill disposal selected., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Synchrotron radiation-induced micro-X-ray analysis were applied to characterize the newly formed phases that precipitate in a passive treatment system using magnesium oxide to remove high concentrations of zinc (ca. 440 mg/L) and other minor metals from neutral pretreated waters in the Iberian Pyrite Belt (SW Iberian Peninsula). Micro-X-ray fluorescence (μ-XRF) maps of polished samples were used to find spatial correlations among metals, pinpointing zones of interest where micro-X-ray diffraction (μ-XRD) data were exploited to identify the mineral phases responsible for metal retention. This coupled technique identified hydrozincite (Zn(5)(CO(3))(2)(OH)(6)) and minor loseyite ((Mn,Zn)(7)(CO(3))(2)(OH)(10)) as the mineral sinks for Zn and also other potentially toxic elements such as Co and Ni. Although hydrozincite retains traces of Mn, this metal is mainly retained by precipitation of loseyite. The precipitation of zinc hydroxy-carbonates and their ability to uptake other metals (Mn, Co, and Ni) is hence of potential interest not only for the treatment of contaminated waters but also for the generation of a solid waste that could be exploited as a new Zn economic resource.

The Tinto and Odiel rivers are seriously affected by acid mine drainage (AMD) from the long-term mining activities in Iberian Pyrite Belt (IPB). As a consequence, the Huelva estuary is heavily contaminated by metals and metalloids. This study presents an estimation of the seasonal variation, and the dissolved contaminant load transported by both rivers from February 2002 to September 2004. Besides, toxicity and bioaccumulation tests with the sediments of the estuary have been conducted in order to measure the mobility of the toxic metals. Results show that the Tinto and Odiel rivers transport enormous quantities of dissolved metals to the estuary: 7900 t yr(-1) of Iron (Fe), 5800 t yr(-1) Aluminium (Al), 3500 t yr(-1) Zinc (Zn), 1700 t yr(-1) Copper (Cu), 1600 t yr(-1) Manganese (Mn) and minor quantities of other metals and metalloids. These values represent 37% of the global gross flux of dissolved Zn transported by rivers in to the ocean, and 15% of the global gross flux of dissolved Cu. These metals and metalloids usually sink in the estuarine sediments due to pH and salinity changes. The increase of salinity in the estuary favours the adsorption and trapping of metals. For this reason, the mobility and bioavailability of metals such as Zn, Cd and Cu is higher in sediments located in the area of fresh water influence that in sediments located in the marine influenced area of the estuary, showing a higher percentage of fractionation and bioaccumulation of these metals in the station influenced by the fresh water environment.

The Tinto and Odiel Rivers are strongly affected by acid mine drainage (AMD) due to the intense sulphide mining developed in their basins over the past 5000 years. In this study the results obtained from a weekly sampling in both rivers, before their mouth in the Ría of Huelva, over three and a half years of control are analysed. In the Tinto River, the concentrations of sulphates, Al, Cd, Co, Li and Zn are double to those of the Odiel as a consequence of lower dilution. However, the concentration of Fe in the Odiel River is 20 times lower, since the precipitation of Fe oxyhydroxysulphates caused by neutralisation processes is more intense. Lower As, Cr, Cu and Pb concentrations are also found in the Odiel River as, to a greater or lesser extent, they are sorbed and/or coprecipitated with Fe. Other elements such as Be, Mn, Ni and Mg show similar values in both systems, which is ascribed to lithological factors. The seasonal evolution of contaminants is typical of rivers affected by AMD, reaching a maximum in autumn due to the dissolution of evaporitic salts precipitated during the summer. Nevertheless, in the Tinto River, Ca, Na and Sr show a strong increase during the summer, probably due to a greater water interaction with marly materials, through which the last reach of the river flows. Barium has a different behaviour from the rest of the metals and its concentration seems to be controlled by the solubility of barite. Iron, As and Pb show different behaviours in both rivers, those for Fe and As possibly linked to the prevalence of different dissolved species of Fe. The different Pb pattern is probably due to the control of Pb solubility by anglesite or other minerals rich in Pb in the Tinto River.