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Los ríos que drenan la Faja Pirítica Ibérica (FPI) presentan un grave problema de contaminación por aguas ácidas procedentes de minas de sulfuros abandonadas. La construcción de la presa de Alcolea, localizada en el río Odiel, se empezó en 2014 pero se paralizó en 2017, aunque actualmente hay una fuerte presión de los regantes para que se retome. Debido a la acidez que presenta el río Odiel existe una gran polémica sobre la calidad del agua de este embalse. En este trabajo se investiga la calidad del agua en los grandes embalses de la FPI a partir de la información analítica de la red oficial de control de calidad. Los embalses no afectados por aguas ácidas (Jarrama y Corumbel) tienen valores de pH próximos a neutros y muy baja concentración de sulfatos (

Bariatric surgery generates a large weight loss. It is considered a successful surgery when 50% of the excess weight loss is reached. However, this measure does not include some variables that may have a direct impact on a patient’s health, such as fat-free mass (FFM) or bone mass. Therefore, the aim of this study is to evaluate body composition and bone mass in patients undergoing one-anastomosis gastric bypass (OAGB). A prospective observational study was performed in patients undergoing OAGB. Body composition and bone mass were evaluated by bioelectrical impedance analysis at baseline (1 day prior to surgery), at 6 and 12 months after surgery. A total of 94 patients (67% females and 33% males) were included in the study. The excess BMI loss at 6 and 12 months after surgery was 97.9 ± 20.1% and 110.2 ± 30.5% respectively. The FFM showed a reduction of 6.6 ± 4.8 kg (p

The treatment of acid mine drainage in sulphide mining generates large amounts of metal-rich sludge whose management suppose an environmental quandary worldwide. Although traditional practices have focused on safe disposal in landfills, more environmentally friendly solutions may be adopted. The environmental performance of these solutions can be evaluated using tools like Life Cycle Analysis (LCA) that allows the estimation of the cumulative environmental impacts resulting from all stages in the product life cycle. The main goal of this study is, for the first time, to perform a LCA on different management strategies (i.e., i), encapsulation and disposal in landfill; ii) metal recovery using a chemical scheme; iii) pellets manufacturing for phosphorus removal from wastewaters; and iv) brick fabrication) for the metal-rich sludge generated from an active treatment plant. The manufacturing of pelletized material exhibited the lowest impacts (−35 REQs) due mainly to the environmental benefits of wastewater treatment. Despite the undoubtedly economic interest of recovering metals from the sludge, this route exhibited the highest environmental impacts (38 REQs), especially in the categories of fossil depletion (20,943 kg oil eq), marine (64 kg 1,4-dB eq) and freshwater ecotoxicity (50 kg 1,4-dB eq) due to the use of toluene and trybutylphosphate (TBP). The manufacture of bricks could be also an alternative route by obtaining economic value while exhibiting low environmental impacts (0.32 REQs), mainly on marine and freshwater ecotoxicity (0.7 kg 1,4-dB eq). These impacts can be notably reduced if waste materials are used replacing clays or using renewable energies. The encapsulation of these wastes is also a suitable option with a low environmental impact (0.46 REQs), but slightly greater than the brick manufacturing and with no economic return., This work was supported by the Spanish Ministry of Economic and Competitiveness through the projects CGL2016-78783-C2-1-R (SCYRE) and by H2020 European Institute of Innovation and Technology (EIT RawMaterials) through the projects Modular recovery process services for hydrometallurgy and water treatment (MORECOVERY). C.R C´anovas thanks the Spanish Ministry of Science and Innovation for the Postdoctoral Fellowship granted under application reference RYC2019- 027949-I. F. Macias was funded by the R&D FEDER Andalucía 2014–2020 call through the project RENOVAME (FEDER; UHU- 1255729). The authors would also like to thank to Dr. Roland Hischier (Associate Editor) for its kindly handling and four anonymous reviewers for their helpful comments and suggestions that improved the quality of the manuscript. Funding for open access charge: Universidad de Huelva / CBUA

In the salth-marshes of the Tinto River (Huelva estuary, SW Spain), are stored in stacks around 100 Mt of PG, covering a surface of 1000 ha without any type of isolation, which produce an important impact in the surrounding environment. On the other hand, this ecosystem it is affected by acid mine drainage (AMD) from sulphide mines located upstream the Tinto River. The aim of this study is to evaluate the deep pollution of the underlain salt-marsh sediments due to leachates from the PG stacks. For that purpose, 7 cores were collected from zones 2 and 3 of the stacks, and PG and salt-marsh sediments samples from different depths were analyzed. The physicochemical parameters, mineralogy, granulometry and the concentration of the main elements of interest were determined in the samples. Most analysed salt-marsh sediments are not affected by PG stacks pollution, because sediments act as a “barrier” for the leachates from the PG, concentrating the contaminants in the first decimetres (0.5 m) under PG-sediments contact, and the deep infiltration is very limited. The obtained results suggest that the perimeter channel which is projected to build in the restauration project, should has a depth of 1 m below the level of the PG stacks for assuring the complete collection of leachates from the stacks, and avoid their liberation into the Tinto River estuary.

This paper investigates the paleoenvironmental evolution of a core extracted in the middle sector of the Tinto River estuary, SW Spain, one of the most polluted areas in the world due to mining over thousands of years (>4 kyr BP) and recent industrial discharges. This evolution includes alluvial sands (>6.4 cal kyr BP), bioclastic sands and silts deposited in subtidal and intertidal channels during and after the Holocene transgression maximum (6.4-4.3 cal kyr BP), the sedimentation of clayey-sandy silts in low and high marshes during the last 2.4 kyr BP and a final anthropic filling. Three sharp peaks of pollution have been detected, representing a) a natural origin during the Holocene transgression; b) the impact of the first mining activities (~4.5 cal kyr BP); and c) the effect of industrial discharge and a new period of mining activity throughout the 19th and 20th centuries. Foraminifera, ostracods and molluscs disappeared during these last two peaks., Este trabajo investiga la evolución paleoambiental inferida a partir del estudio de un testigo extraído en el sector medio del estuario del río Tinto (SO de España), una de las zonas más contaminadas del mundo por actividades mineras milenarias (>4 kyr BP) y descargas industriales recientes. Esta evolución incluye arenas aluviales (>6.4 cal kyr BP), arenas bioclásticas y limos depositados en canales submareales e intermareales durante y después del máximo transgresivo holoceno (6.4-4.3 cal kyr BP), la sedimentación de limos arcillosos-arenosos marismeños durante los últimos 2.4 kyr BP y un relleno antrópico final. Se han detectado tres picos de contaminación, que proceden de: a) un origen natural durante el máximo transgresivo holoceno; b) el impacto de las primeras actividades mineras (~ 4.5 kyr BP); y c) el efecto conjunto de los vertidos industriales y un nuevo período de actividad minera durante los siglos XIX y XX. Los foraminíferos, ostrácodos y moluscos desaparecieron durante estos dos últimos picos.

Opencast mining of sulfide ore deposits may lead to the formation of anthropogenic acidic lakes with highly polluted waters. In these systems, it is crucial to understand the hydrological connections between surface and groundwater and their contribution to the pollutant load delivered to the downgradient streams. This study characterizes the interactions between surface and groundwater in an acidic pit lake using different geochemical tracers (i.e., REE and other trace metals). The San Telmo pit lake, located in one of the most pollutant sources of the Iberian Pyrite Belt (IPB), can be considered as a flow-through pit lake except during dry periods, when it behaves as a terminal lake due to lower inputs by surface waters and higher outputs by evaporation. Results based on geochemical tracers indicate that the main inputs to the pit lake come from surface waters, with minor groundwater inputs rich in As, Cr, Cu, Fe and Pb. The contaminant load released from the mining area is very high (e.g., median values of 520 kg/day of Fe and 38 kg/day of Zn), causing the degradation of the fluvial network downstream. Most of released pollutants come from waste dumps located at the W of the mining zone (~50-70% of Al, Cd, Mg, Mn, Ni, SO

The Odiel and Tinto rivers show singular characteristics due to the significant acid mine drainage (AMD) generated in the first section of their basins and the phosphogypsum (PG) stacks located on their common estuary. AMD leads to low pH and high redox potential, which keep high amounts of toxic elements and radionuclides in dissolution. The objective of this work was to analyse the seasonal evolution of U-Th isotopes and 210Po in these rivers and the estuarine mixing zone. Four sampling points were selected (a fluvial point and an estuarine one for each river) and water samples were collected monthly throughout a year. The concentrations of natural radionuclides in the dissolved and particulate phases were determined by alpha spectrometry. The Odiel and Tinto rivers show concentrations of U-Th isotopes and 210Po from one to three orders of magnitude higher than background continental waters due to the strong effect of AMD, and 234U/238U activity ratios up to 2. The studied radionuclides show a clear seasonal behaviour in these rivers, with three different stages during the year: (1) concentration peaks observed during November and December due to the “washing effect” produced by the first rainfalls of the hydrological year, (2) a “dilution effect” by runoff in the rainy winter, and (3) a progressive “concentration effect” during the spring and summer. A non-conservative behaviour of the analysed radionuclides in the estuaries was demonstrated due to precipitation processes produced by the increase of pH. The polluted outflows from the PG stacks located in the Tinto estuary produce a significant radioactive impact, mainly during the rainiest months, increasing the concentration of U-isotopes and 210Po in the particulate phase.

This paper addresses the behaviour of several technology critical metals (TCMs), i.e., rare earth elements (REEs), Y, Sc, Ga and Tl, in the Tinto River (SW Spain), quantifying their fluxes to the Atlantic Ocean and unravelling the governing geochemical processes controlling their solubility. To accomplish this goal, a high-resolution (2–24 h) sampling was performed during the hydrological year 2017/18. Mean dissolved concentrations of 380 μg/L of REE, 99 μg/L of Y, 15 μg/L of Sc, 9.2 μg/L of Ga and 4.8 μg/L of Tl were found. Most TCMs followed a behaviour similar to that of sulphate and base metals throughout the year, exhibiting a quasi-conservative behaviour due to acidic conditions. However, dissolved Tl concentrations seem to be strongly controlled by Tl incorporation onto secondary minerals and diatoms deposited on the riverbed, especially during the dry season. The remobilization of riverbed sediments led to the transport of significant amounts of TCMs associated with particulate matter, especially Al oxy-hydroxy-sulphates or Al-silicates rather than Fe precipitates (except for Tl and Ga). Around 5.8 t of REE, 1.3 t of Y, 248 kg of Sc, 139 kg of Ga and 138 kg of Tl were delivered annually in their dissolved forms by the Tinto River to the Atlantic Ocean, which constitutes around 0.09% of the dissolved global flux into the oceans of Y, 0.02% of the REE flux, 0.01% of the Ga flux and 0.001% of the Sc flux., This work was supported by the Spanish Ministry of Economy and Competitiveness through the research projects SCYRE (CGL2016- 78783-C2-1-R),CAPOTE (CGL2017-54686050- R) and VALOREY (RTI2018 -101276-J-I00).The authors thank to Dr. Damiá Barceló (Co-Editor- in-Chief) and three anonymous reviewers for their helpful comments that notably improved the quality of the original manuscript., This work was supported by the Spanish Ministry of Economy and Competitiveness through the research projects SCYRE (CGL2016-78783-C2-1-R), CAPOTE (CGL2017-86050-R) and VALOREY (RTI2018-101276-J-I00). The authors thank to Dr. Damiá Barceló (Co-Editor-in-Chief) and three anonymous reviewers for their helpful comments that notably improved the quality of the original manuscript.

Acid mine drainage (AMD) due to the mining of sulfide deposits is one of the most important causes of water pollution worldwide. Remediation measures, especially in historical abandoned mines, require a deep knowledge of the geochemical characteristics of AMD effluents and metal fluxes, considering their high spatial and temporal evolution, and the existence of point and diffuse sources with a different response to rainfall events. This study investigates the temporal variations and hydrogeochemical processes affecting the composition of main AMD sources from the Tharsis mines (SW Spain), one of most important historical metal mining districts in the world. To address this, a fortnightly-monthly sampling was performed during two years in the main AMD sources and streams within the mine site covering different hydrological conditions. A seasonal pattern was observed linked to hydrological variations; higher pollutant concentrations were observed during the dry season (maximum values of 4,6 g/L of Al, 11,8 g/L of Fe, and 67 g/L of sulfate) and lower ones were observed during the rainy periods. Stream samples exhibited a negative correlation between electrical conductivity (EC) and flow, while positive values were observed in AMD sources, where groundwater fluxes were predominant. High flow also seems to be the main driver of Pb fluxes from AMD sources, as the concentration of Pb in waters increased notably during these events. The precipitation of secondary Fe minerals may limit the mobility of As and V, being retained in the proximity of mine sites. The concentration of Zn in waters seems to be controlled by the original grade in the metal deposit from which the waste is generated, together with the age of these wastes. The pollutant load delivered by the Tharsis mines to the surrounding water courses is very high; e.g., mean of 733 ton/yr of Al or 2757 ton/yr of Fe, deteriorating the streams and reservoirs downstream., This work was supported by the Spanish Ministry of Economic and Competitiveness through the projects CGL2016-78783-C2-1-R (SCYRE) and by H2020 European Institute of Innovation and Technology (EIT RawMaterials) through the projects Modular recovery process services for hydrometallurgy and water treatment (MORECOVERY). C.R Canovas thanks the Spanish Ministry of Science and Innovation for the Postdoctoral Fellowship granted under application reference RYC2019- 027949-I. F. Macias was funded by the R&D FEDER Andalucía 2014–2020 call through the project RENOVAME (FEDER; UHU-1255729). Funding for open access charge: Universidad de Huelva/CBUA

The Olivargas River drains materials from the Iberian Pyrite Belt with a large number of abandoned sulphide mining complexes that produce highly contaminated acid mine drainages (AMD). The Olivargas River is regulated by a reservoir that receives these acid leachates through its three main tributaries. In this study, the chemical composition of the waters from the reservoir and the water courses in its watershed are investigated based on samples taken throughout a hydrological year. We calculated the contaminant load for Al, Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn, SO4 and other elements entering the reservoir by two methods, establishing the relations of the dissolved element concentrations with 1) the water flow and 2) the specific conductance. The most extreme conditions were found in the tributary Los Peces Creek, with a mean pH value of 2.8 and concentrations of up to 736 mg/L of Zn and 291 mg/L of Al, making it the main source of metals in the reservoir (up to 65 t/year of Zn). Given that the volume of acid mine water pouring into the reservoir is relatively low, the water pH in the reservoir remains neutral. Under these conditions, most of the mine-derived metals (especially Al and Fe) form precipitates that accumulate in the bottom sediments, while dissolved concentrations are low (0.2 mg/L of Al and

The failure of the tailing dam at the Aznalcóllar mine (SW Spain) in 1998 released ≈ 6 million m3 of pyrite sludge and acidic waters, and caused an enormous environmental disaster in the Agrio and Guadiamar rivers. A small aquifer formed by recent alluvial materials deposited by both rivers was also affected. The mine closed as a result of the spill but a new project for its reopening is currently being developed. The area covered by the spill (≈ 60 km long) was later transformed into a protected green corridor, which connects two important natural reserves. This work describes the effectiveness of the remediation measures taken and analyzes the evolution of water quality in the area since 1980 (almost 20 years before the accident occurred). The contaminant levels in both surface and groundwater showed a sharp decrease the first years after the spill, followed by a subsequent stabilization of pollution levels. Nowadays, pollutant concentrations in surface waters are even lower than those recorded before the spill, due to the cessation of mining and the effectiveness of the remediation. Despite this fast and outstanding improvement, the alluvial aquifer close to the mining zone is still polluted, with acidic pH values in some areas, probably due to the slow movement of groundwater together with the existence of some areas with polluted soils. As this aquifer feeds the streams, some pollutants (e.g. Al, Cd, and Zn) reach the surface waters. Remediation of the polluted soils as well as the alluvial aquifer in this sector is strongly recommended to achieve the complete rehabilitation of the affected area.

The R&iacute, o Tinto, located in the Iberian Pyrite Belt (SW Spain), constitutes an extreme case of pollution by acid mine drainage. Mining in the area dates back to the Copper Age, although large-scale mining of massive sulfide deposits did not start until the second half of the 19th century. Due to acidic mining discharges, the R&iacute, o Tinto usually maintains a pH close to 2.5 and high concentrations of pollutants along its course. From a detailed sampling during the hydrological year 2017/18, it was observed that most pollutants followed a similar seasonal pattern, with maximum concentrations during autumn due to the washout of secondary soluble sulfate salts and minimum values during large flood events. Nevertheless, As and Pb showed different behavior, with delayed concentration peaks. The dissolved pollutant load throughout the monitored year reached 5000 tons of Fe, 2600 tons of Al, 680 tons of Zn, and so on. While most elements were transported almost exclusively in the dissolved phase, Fe, Pb, Cr, and, above all, As showed high values associated with particulate matter. River water quality data from 1969 to 2019 showed a sharp worsening in 2000, immediately after the mine closure. From 2001 on, an improvement was observed.

The Tharsis mine is presently abandoned, but the past intense exploitation has left large dumps and other sulphide-rich mining wastes in the area generating acid mine drainages (AMD). The main goal of this work is to study the effect of hydrogeochemical processes, hydrological regime and the waste typology on the physicochemical parameters and dissolved concentrations of pollutants in a deeply AMD-affected zone. Extreme leachates are produced in the area, reaching even negative pH and concentrations of up to 2.2 g/L of As and 194 g/L of Fe. The results of the comparison of ore grades of sulphide deposits with dissolved concentrations in waters shows that Pb is the least mobile element in dissolution probably due to the precipitation of Pb secondary minerals and/or its coprecipitation on Fe oxyhydroxysulphates. Arsenic, Cr, and V are also coprecipitated with Fe minerals. Seasonal patterns in metal contents were identified: elements coming from the host rocks, such as Al, Mn and Ni, show their maximum values in the dry period, when dilution with freshwater is lower and the interaction of water-rock processes and evaporation is higher. On the other hand, As, Cr, Fe, Pb and V show minimum concentrations in the dry period due to intense Fe oxyhydroxysulphate precipitation. In this sense, large sulphide rich waste heaps would be a temporal sink of these elements (i.e. Pb, As, Cr and V) in the dry period, and a significant source upon intense rainfalls., This work was supported by the Spanish Ministry of Economic and Competitiveness through the projects CGL2016-78783-C2-1-R (SCYRE) and by H2020 European Institute of Innovation and Technology (EIT RawMaterials) through the projects Modular recovery process services for hydrometallurgy and water treatment (MORECOVERY). The authors thank to Prof. Yong Sik Ok (Associate Editor) and five different reviewers for their helpful comments that notably improved the quality of the manuscript.

Opencast mining operations frequently lead to the creation of large voids that become anthropogenic lakes when the water table recovers. In the case of sulfide mining the stored water is of an acidic nature with significant concentrations of toxic metals and, therefore, a high pollutant potential. The main goal of the present work is to characterize the hydrological functioning and evolution of four acidic mine pit lakes in the abandoned mines of Tharsis, which is the second most important mine district in the Iberian Pyrite Belt (IPB). We present a simple methodology based on the use of the available orthophotographs and a Digital Terrain Model (DTM) together with the water balance of the pit lakes, which could be applied to other abandoned mining sites, where there is often a lack of hydrogeological information that prevents the application of more complex models. The accumulation of large volumes (5.2 × 10 6 m 3 ) of acidic and metal-rich waters in these pit lakes poses a serious environmental concern, with dissolved concentrations up to 2000 mg/L of Fe, 223 mg/L of Al, etc. Sierra Bullones and Filon Norte are connected underground and present the same evolution, with water transfers from Sierra Bullones to Filon Norte. The water level in both pit lakes is increasing, with an average rise of 2.8 m/yr since the beginning of flooding. However, the increase in the evaporation rate, as a result of the larger flooded area as the water level rise, would induce a hydrological equilibrium before reaching the overflow level, leading to the formation of a terminal lake. On the other hand, the water level in Filon Centro and Filon Sur pit lakes remain approximately stable. The first behaves as a flow-through or terminal lake, depending on the annual rainfall, while the second acts permanently as a flow-through lake.

This study characterizes the hydrogeochemical behavior of one of the most pollutant sources in the Iberian Pyrite Belt, namely, the Poderosa adit outflow. This artificial spring arises from an anthropogenic mine aquifer with a similar hydrogeological behavior to karstic systems, where the infiltration area is an endorheic zone and the aquifer shows allogenic recharge. Recent mining has markedly increased the contaminant levels. The pollutant load released from the adit to the receiving water body is very high, with average loads of 280 kg/day of Fe, 47 kg/day of Al, 17 kg/day of Cu and so on. However, a high variability is observed related to hydrological and geochemical factors, especially during intense rainy episodes. Thus, the pollutant load during these events suffers a dramatic increase, i.e., from ~100–200 kg/day of Fe during base flow to almost 2200 kg/day during the flow peak. These data highlight the importance of short but intense rainy events on metal fluxes from mining areas, which has been previously reported in surface waters but scarcely reported in mine adits, with expected lower response times to rainfall. The pollutant load released by non-point sources, i.e., spoil heaps, is lower than that released from the adit most of the year, although it increased noticeably during intense rainy events. Some remediation measures were adopted during the 1990s without a suitable hydrogeological characterization and were shown to be ineffective. On the basis of the obtained results, potential restoration measures are discussed.

Total and dissolved rare earth elements (REE) were studied in a river reach affected by several inputs of acid mine drainage. The first four acidic discharges were of lesser importance compared to the last (Agrio River, coming from the Rio Tinto mines), which transported high loads of Fe and Al (2.1 and 4.2 ton/day, respectively) together with REE (16.4 kg/day) and other trace elements. In the acid mine drainage (AMD) sources, practically all the REE were dissolved and the North American Shale Composite (NASC)-normalized patterns showed an enrichment in medium REE, although some differences exist between the patterns of each source. The pH values in the river reach upstream of the confluence with the Agrio River ranged between 8.01 and 7.03, and most of the Fe and Al from the AMD sources precipitated. Downstream of this acidic discharge, the pH decreased to 2.98. Upstream of the first AMD input, the dissolved and total concentrations of ΣREE were very low ( 7, concentrations of ΣREE increased (up to 25 μg/L), mainly transported by the particulate phase. In the reach downstream of the Agrio River with acidic conditions, REE behaved conservatively. The REE NASC-normalized patterns of the river samples resemble that of the AMD sources, although an enrichment of heavy REE in the dissolved phase is observed linked to complexation by carbonates. Cerium and particularly La also show higher dissolved percentages, similar to HREE, which must be due to the lower affinity of these elements to be sorbed onto Fe oxyhydroxides. Variations in Ce and Eu anomalies are observed along the river reach as a consequence of the different AMD inputs. However, the values of the Ce anomaly are higher in total samples than in dissolved samples. Speciation results indicate that these differences are not caused by differences in oxidation states but by slight differences in the hydrogeochemical behaviour of Ce with respect to La and Nd.

This study aims to characterize geochemically the acid mine drainage (AMD) sources causing deterioration of the water quality of a river reach with extreme hydrologic variability and to identify the patterns of dissolved and particulate contaminants along the reach. The hydrochemistry of the river reach is exposed to dramatic seasonal and spatial changes. The levels of sulfate and metals increase progressively along the reach due to the input of the first AMD discharges. However, the confluence with the Agrio River, which collects extremely acidic and metal-rich AMD from Riotinto mines, causes the total depletion of alkalinity and a dramatic decrease of pH values (down to 3.3), which strongly enhances the solubility of metals. A pH-controlled pattern of metal transport prevails in the river. Above pH 6, particulate Al and Fe is the predominant form of transport in the river; below pH 5, Al is chiefly transported in dissolved form, while the water velocity may control sedimentation of Fe precipitates. Particulate Cu, Zn, and Mn exhibit a similar pattern although with some differences. Above pH 6, Cu is generally transported by the particulate phase, while Zn and to a greater extent Mn, are mostly carried by the dissolved phase. Cobalt and Ni are mostly transported in dissolved form, even at circumneutral pH values, showing a more conservative behavior. Geochemical modeling results and analysis of high-energy X-ray diffraction patterns point to schwertmannite and ferrihydrite as the mineral phases responsible for the solubility control of Fe. Schwertmannite may precipitate close to mixing zones, where lower pH values and higher sulfate concentrations are found, while ferrihydrite probably precipitates farther from these zones, at higher pH values and lower sulfate concentrations. Metal and sulfate loadings are strongly linked to rainfall events. The highest dissolved loads were observed during floods in May 2016, when up to 48 t day−1 of Al, 16 t day−1of Fe, 8.4 t day−1of Zn, and so on, were transported by the river, values noticeably higher than those observed in other mining areas.

Fluxes of acidity and contaminants from acid mine drainage (AMD) sources to the receiving surface water bodies were studied in a mining-impacted watershed (Meca River, SW Spain) using a novel methodology based on the joint application of EMMA and MIX codes. The application of EMMA and elemental ratios allowed delimiting the end-members responsible for water quality variations at a catchment scale. The further application of MIX quantified the significant impact of AMD on the river quality; less than 10% of AMD relative contribution is enough to maintain acidic conditions during most of the year. The mixing model also provided information about the element mobility, distinguishing those elements with a quasi-conservative behavior (e.g., Cu, Zn, Al, Co or Ni) from those affected by mineral precipitation/dissolution (e.g., K, Si, Na, Sr, Ca, Fe, Pb, or As). Floods are the main driver of dissolved and, mainly particulate, contaminants in the catchment. Thus, the first rainfall events in November only accounted for 19% of the annual Meca flow but yielded between 26 and 43% of the net acidity and dissolved metal loads (mainly, Fe, As and Pb). Concerning particulate transport, around 332 tons of particulate Fe, 49 tons of Al, 0.79 tons of As and 0.37 tons of Pb were recorded during these first floods. The particulate As concentration can be up to 34 times higher than the dissolved one during floods and between 2 and 4 times higher for Fe, Pb and Cr. This integrated modeling approach could be a promising and useful tool to face future restoration plans in derelict mines worldwide. This approach would allow prioritizing remedial measures, achieving an environmental and cost-effective restoration of degraded areas.

This work deals with the distribution of rare earth elements (REE) in the abandoned Tharsis mines under different hydrological conditions. High concentrations of REE were observed; mean value of 1747 μg/L. The highest concentrations of REE were recorded during the dry period (DP, mean of 2220 μg/L) due to high evaporation and strong water-rock interactions. However, some sampling points showed the highest REE concentrations during the wet period (WP) due to the washing out of large dumps during intense rainfall. The concentration of REE shows a positive correlation with electrical conductivity (EC) and a negative correlation with pH because more acidic conditions enhance dissolution of minerals. However, the highest concentrations of REE occurred in samples with intermediate levels of metal pollution and EC values. The highest correlations of middle REE (MREE) and heavy REE (HREE) occurred with elements related to hydrothermal mineralisation of Mn and Ni, associated with sulphide deposits. The normalised patterns of the AMD sources showed an enrichment of MREE over light REE (LREE) and HREE in all samples. The use of REE patterns as geochemical tracers confirmed the conservative behaviour of REE in the fluvial network, that is, they are not affected by the precipitation of mineral phases. The quantification of REE released from AMD sources to water bodies reveals that, although the highest concentrations occur during the DP, the main load of REE occurs during the WP, due to the highest discharges, with 6.62 kg/day of LREE, 1.12 kg/day of MREE, and 0.54 kg/day of HREE., This work was supported by the Spanish Ministry of Economic and Competitiveness through the projects CGL2016-78783-C2-1-R (SCYRE) and by H2020 European Institute of Innovation and Technology (EIT Raw Materials) through the projects Modular recovery process services for hydrometallurgy and water treatment (MORECOVERY). The authors would like to thank to Prof. Klaus Kümmerer (Editor) and three different reviewers for their helpful comments that notably improved the quality of the manuscript.

Next to the city of Huelva (SW of Spain), around 100 Mt of phosphogypsum (PG) are stored in stacks on the salt-marshes of the Tinto River estuary covering a surface of about 1000 ha. Due to the high content of 238U series natural radionuclides of the PG, its acidic nature (pH about 3), and the fact that PG stacks were disposed without any kind of isolation from the substrate, they could produce a potential radioactive impact into the underlying sediments. The aim of this work is to assess the pollution of the underlying sediments by natural radionuclides coming from the PG stacks. To this end, seven cores were taken, and PG and sediments samples collected at different depths were analysed. The activity concentrations of the main long half-live natural radionuclides of interest were determined by applying both gamma-ray and alpha-particle spectrometry radiometric techniques. The results of this study showed that the first decimeters of salt-marsh sediment act as a “barrier” for the radionuclides coming from the PG stacks decreasing rapidly its activity concentration in depth, affecting mainly sediments located in the first 20 cm below the contact due to mixing processes. While 230Th, 226Ra and 210Pb pollution is mainly restricted to the first 20 cm of sediments, U-isotopes can reach higher depths (up to around 50 cm) by leaching processes due to their lower reactivity and higher concentration in the polluted leachates. The obtained results have high relevance for the design of the perimeter channel which is projected to build in the restoration project, suggesting that should has around 1 m deep under the base of the PG stacks, to ensure the full collection of polluting leachates, and to prevent their release into the estuary of the Tinto River.

Acid Mine Drainage (AMD) generates a great concern worldwide due to its severe impact to water resources during hundreds and even thousands of years after the cessation of mining activity if control measures are not implemented. AMD treatment is an environmental necessity, but also constitute a tremendous opportunity for the valorization of potential secondary sources of elements of economic interest. The knowledge of the hydrogeochemistry of REE in AMDs and their distribution using normalized patterns would help discrimination of the most potentially marketable AMD sources. To achieve this goal and to estimate the total economic potential of a severely AMD-affected region, chemistry and flow data were determined in spatially and temporally-distributed samples of numerous AMD sources collected throughout the Iberian Pyrite Belt (IPB). Due to high anual metal loads of elements such as Al (6600 ton), Zn (1600 ton), Cu (600 ton), Co (26 ton), Ni (10 ton), LREE (10.7 ton/yr), MREE (2.1 ton/yr), HREE (1 ton/yr), Y (3.7 ton) or Sc (0.7 ton), AMDs of the IPB would have an economic potential of 24.1 M$/yr (being REE 22.6% of this potential). Although the technical and economic limitations would impose a more realistic value of 4.2–10.3 M$/yr. The magnitude of this economic potential cannot be compared with active mines, however the longevity of the AMD generation processes and the need to achieve an environmental improvement make valorization of these leachates an interesting option to recover metals, which would help to treatment plants costs, improving notably the quality of water bodies in abandoned mining sites., This work was supported by the Spanish Ministry of Economy and Competitiveness through the research projects SCYRE (CGL2016-78783-C2-1-R) and CAPOTE (CGL2017-86050-R); and the MORECOVERY (H2020-EIT-PN 18190) project of the European Institute of Technology Raw Materials programme. F. Macías was funded by the R&D FEDER Andalucía 2014–2020 call through the project RENOVAME (FEDER; UHU-1255729). We would also like to thank Dr. Stefano Albanese (Editor-in-Chief), Dr. Annika Parviainen (Guest Editor) and two anonymous reviewers for the support and suggestions that significantly improved the quality of the original paper.

Sulfide-mining wastes may lead to severe environmental and human health risks, especially challenging in abandoned mines without environmental regulation. This work is aimed at discussing the environmental problems associated with this type of wastes, the risks posed by metal(loid) exposure to living organisms, as well as the measures available to mitigate such risks, taking the case of the Iberian Pyrite Belt (SW Iberian Peninsula), as an example, worldwide. The release of metal(loid)s from these wastes upon weathering is strongly controlled by mineral assemblage, processing technique, grain size distribution, and occurrence of highly reactive secondary minerals. Exposure to these wastes may pose a severe risk for humans and animals, and thus, remediation measures must be adopted in abandoned mines. Among these measures, recovery of valuable metals from sulfide wastes could be a promising environmentally friendly solution; however, grade and mineralogical siting of valuable metals, as well as selective recovery methods, must be site-by-site investigated.

On August 3, 1492, Christopher Columbus departed from the port of Palos de la Frontera, located in a small cove in southwestern Spain, and returned to this same port on March 15, 1493. On the basis of sedimentology, geochemistry, paleontology and dating of a long core (18 m) collected in this cove, thirteen facies are distinguished in the Neogene-Holocene evolution of its sedimentary infilling, with a transition from Miocene marine environments to Late Holocene marshes, going through an intermediate period that includes fluvial gravels, alluvial sediments and shallow coastal deposits that characterize the maximum of the Fladrian transgression in this area (~6.5 cal kyr BP). These data and others contributed by historical sources allow an approximate reconstruction of this cove at the end of the 15th century.

Waters affected by acid mine drainage (AMD) can contain high concentrations of rare earth elements (REE) which have a great interest not only by its application as tracers in hydrogeochemical processes but also as a potential economic resource. The Iberian Pyrite Belt (IPB) is rich in sulfide deposits which have been exploited intensively since ancient times, generating numerous AMD discharges. This work studies the REE content in five different AMD sources located in the upper reach of the Odiel River (SW Spain). The concentration of REE in these sources ranged from 113 to 7208 ppb. Differences in NASCnormalized REE patterns were observed among AMD sources that remained constant along the year despite the variability in REE concentrations, being lower during the rainy season due to dilution processes., This work was financed by the Spanish Ministry of Economy and Competitiveness through the project EMPATIA (Ref. CGL2013-48460-C2-1-R) and the grant BES-2014-068354.

Summary The Odiel watershed drains materials belonging to the Iberian Pyrite Belt, where significant massive sulfide deposits have been mined historically. As a result, a huge amount of sulfide-rich wastes are deposited in the watershed, which suffer from oxidation, releasing acidic lixiviates with high sulfate and metal concentrations. In order to reliably estimate the metal loadings along the watershed a complete series of discharge and hydrochemical data are essential. A hydrological model was performed with SWAT (Soil and Water Assessment Tool) to solve the scarcity of gauge stations along the watershed. The model was calibrated and validated from daily discharge data (from 1980 to 2010) at the outlet of the watershed, river inputs into an existent reservoir, and a flow gauge station close to the northern area of the watershed. Discharge data obtained from the hydrological model, together with analytical data, allowed the estimation of the dissolved pollutant load delivered annually by the Odiel River (e.g. 9140 t of Al, 2760 t of Zn). The pollutant load is influenced strongly by the rainfall regime, and can even double during extremely rainy years. Around 50% of total pollution comes from the Riotinto Mining District, so the treatment of Riotinto lixiviates reaching the Odiel watershed would reduce the AMD (Acid Mine Drainages) in a remarkable way, improving the water quality downstream, especially in the reservoir of Alcolea, currently under construction. The information obtained in this study will allow the optimization of remediation efforts in the watershed, in order to improve its water quality.

The aqueous oxidation of sulphide minerals leads to the generation of acid mine drainage (AMD), one of the main causes of water pollution worldwide. Mineral reactivity is greatly enhanced as a result of extraction and processes such as blasting, crushing, and grinding that increase rock surface area. The exposition of sulphide mine wastes to atmospheric conditions enhances AMD generation. However, a large number of processes and factors (e.g., pH, redox conditions, aqueous and surface complexation reactions) may control the mobility of elements in solution. In particular, the formation of soluble secondary minerals may act as transient storage of metals and acidity during AMD generation, leading however to their release upon rainfalls. To study the influence of mineralogy and grain size on the metal release from a variety of sulphide mine wastes collected in the Iberian Pyrite Belt, different grain size samples were treated with distilled water (S:L ratio 1:10) for 24 h simulating rainfall weathering. Results reveal that grain size plays a major role on metal mobility from sulphide mine wastes. However, mineralogical and geochemical evidence points at the partitioning of highly soluble secondary minerals among grain size fractions as the key factor controlling the metal release rate from these wastes. The results obtained show the importance of grain size on the reliability of the different leaching test procedures, and thus encourage standardizing these procedures worldwide., The authors thank two anonymous reviewers for helpful comments that clearly improved the quality of the manuscript, and Associate Editor Encarnación Ruiz-Agudo and Chief Editor Carlos Rodriguez-Navarro for their handling. This work was supported by the Spanish Ministry of Economic and Competitiveness through the projects CGL2016-78783-C2-1-R (SCYRE) and ERAMIN PCIN2015-242. C.R. Cánovas was funded by the Talent Consolidation Program of the University of Huelva. MD Basallote also thanks the Spanish Ministry of Economy and Competitiveness for the Postdoctoral Fellowship granted under application reference FJCI-2015-24765.

Efflorescent sulfate salts constitute a transient storage of acidity and metals during the dry season in mining areas affected by acid mine drainage, especially under semiarid climates. The main goal of this work was to study the metal partitioning among the dissolved and solid phases through the evaporative precipitation sequence of extremely metal-rich mine waters. The evaporative sequence was induced in the laboratory under controlled conditions for 24 days. The loss of water caused a progressive decrease of pH values (from 2.71 to 1.33) and increase of metal concentrations (e.g., from 1826 to 17800 mg/L of Al, 836 mg/L to 9783 mg/L of Fe and 301 to 2879 mg/L of Zn), which caused the precipitation of efflorescent sulfate salts. The precipitated salts were mainly composed of a mixture of minerals of Ca (gypsum, CaSO4·2H2O), Al (alunogen, Al2(SO4)3·17H2O), Fe (copiapite, Fe2+Fe3+4(SO4)6(OH)2·20H2O and melanterite Fe2+SO4·7H2O) and Mg (hexahydrite, MgSO4·6H2O), although the proportion of each mineral phase varied throughout the experiment. A preferential precipitation of Al and Mg sulfate salts, together with melanterite, was observed until the second week of the experiment, with evaporation rates lower than 70%. The precipitation of gypsum predominated with higher evaporation rates, reaching values higher than 80% of the mineral assemblage. The evaporative precipitation sequence was modeled using PHREEQC, obtaining good agreement with experimental data for gypsum, but failing in turn to accurately reproduce the evaporative sequence of other minerals such as hexahydrite, alunogen and melanterite. A metal partitioning pattern was observed during the evaporative precipitation sequence. Fe-sulfate minerals (e.g., copiapite and melanterite) present a higher affinity for Cu, Y and Th (and other trace metals such as Mn, Cd or Sc) while Al and Mg sulfate salts would retain Zn, Co, Ni and to a lesser extent Cr. In the case of gypsum, found prominently in the mineral assemblage during the experiment, it seems to have affinity for REE. This metal partitioning pattern is not observed in field data reported in literature. Such discrepancies, as well as those observed between modeled and experimental results, must be investigated in further studies.

In May 2017, a spill from La Zarza pit lake (SW Spain) resulted in the release of approximately 270,000 m3 of extremely acidic waters to the Odiel River. Around 780 × 103 kg of Fe, 170 × 103 kg of Al, 2.15 × 103 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.

In the Iberian Pyrite Belt (IPB), especially within the Tinto and Odiel River basins, there is a large number of sources of acid mine drainages (AMD), characterised by very extreme pH conditions and pollution levels. This paper studies the main factors governing the composition of the different leachates, based on ionic relationships. Statistically there are no differences between leachates from adits and shafts and other types of AMD sources. The most extreme conditions (pH values near 1, 35 g/L of Fe and 104 mg/L of As) are found in an area of Riotinto covered by milled pyrite wastes, used for the production of copper through leaching. The Cu and Zn ore grades deduced from the leachates are in line with the usual values of the IPB, which indicate a geological control in the composition of the acid mine waters. The lowest SO 4 /Cd and Zn/Cu ratios in the acid leachates are found in the NE of the study area, whereas the minimum values of SO 4 /Ni ratios occur in the center and SW. This seems to be related with the type of deposit: shale-hosted at the southern part of the IPB and felsic volcanoclastic-hosted at the northern part, although there are exceptions to this general pattern. Likewise, the proportions of Fe, Al, Mg, Co, Ni and other elements in the leachates are influenced by the mineralogy and the degree of hydrothermal alteration of each deposit, the latter related with Co/Ni ratio.

The Ri o Tinto drains the eastern part of the Iberian Pyrite Belt (IPB), an area with a huge amount of massive sulphide deposits that has been mined for the last 4500 years. This river presents extreme conditions, with very high concentrations in solution of metals and metalloids and low pH values. Mining activities in the upper part of the watershed of the Ri o Tinto have been documented since historical times and a huge amount of widespread acid-producing mine residues exist in this area. Nevertheless, there is no consensus among the scientific community as to whether the extreme conditions of the Ri o Tinto are the result of natural processes or the intense mining activity in the region. Here we show, using numerous geological, archaeological and historical records, that the present quality of the Ri o Tinto is the result of mining activities, especially during the period 1850-2001, while natural processes of formation of acid rock drainage can be considered negligible.

Compared with pit lakes originated by coal mining, little is known about in-lake neutralization processes in pit lakes from sulfide ore mining in hard rock substrates, which are typically very deep and acidic and receive low carbon (C) inputs and groundwater flows. Physicochemical processes in water and sediments from a pit lake (San Telmo, 130 m deep) in the Iberian Pyrite Belt were investigated. San Telmo is a meromictic and highly acidic (pH 2.8) pit lake due to pH buffering by precipitation of Fe(III) minerals (schwertmannite and jarosite). The sediments have a low abundance of C (below 0.60%) and iron minerals (below 0.12%) compared to most coal-mining pit lakes. In San Telmo sediments, iron reduction and sulfide oxidation may be thermodynamically favored due to low pH values in pore waters (below 3.8) and the presence of reactive iron. Although schwertmannite is the main ferric mineral precipitating in the water column, mineralogical analyses reveal a low abundance of schwertmannite in the sediment. This may be due to the preferential use of this mineral in reduction reactions mediated by bacteria, together with a low replenishment rate of the schwertmannite pool in the sediment. The transformation of reactive iron (schwertmannite and jarosite) into goethite may limit sulfate reduction, promoting acidic conditions in the sediment. As long as the acid mine drainage continues to discharge into the lake, the pH buffering exerted by ferric minerals in the sediments will limit the neutralization of the pH by sulfate reduction.

Extensive extraction of technology critical elements (TCEs) from the lithosphere and their use results in a growing dispersion and remobilisation of these elements within the environmental compartments. We investigated the concentration and mobility of different TCEs (rare earth elements (REEs), Sc, Y, Ga and Tl) in acid mine drainage (AMD) outflows from a massive sulfide underground mine in south-west Spain for around 2 years. High levels of TCEs were observed; average concentrations of 8.2 mg L-1 of REEs, 1.5 mg L-1 of Y, 80 g L-1 of Ga, 53 g L-1 of Sc and 42 g L-1 of Tl were reported, several orders of magnitude higher than those observed in natural waters. The TCEs source in the study site is primarily accessory minerals in the host rocks, although the contribution of Ga and Tl by sulfides cannot be discarded. A seasonal variability in TCEs is observed in AMD waters, although their maximum concentrations do not coincide with those of sulfide-related elements. TCEs seem not to be controlled by the precipitation of secondary minerals, but by the intensity of chemical weathering inside the mined zone. A positive correlation between REEs and the Si/Na+K ratio seems to indicate that these elements are linked to resistant minerals to weathering. © 2019 CSIRO., This work was funded by the H2020 EIT Raw Materials program through the project MORECOVERY “Modular recovery services for hydrometallurgy and water treatment (H2020-EIT-PN 18190)” and by the Spanish Ministry of Science, Innovation and Universities through the SCYRE project (CGL2016-78783-C2-R). C.R. Cánovas was funded by the Talent Consolidation Program of the University of Huelva. MD Basallote also thanks the Spanish Ministry of Science, Innovation and Universities for the Postdoctoral Fellowship granted under application reference FJCI-2015-24765.

Estuaries are very sensitive ecosystems to human activities and the natural evolution of their drainage basins located upstream. Pollution derived from human activities, such as historical mining or recent industrial wastes, can significantly affect their environmental quality. This paper analyzes the silver and copper contents of four cores extracted in two estuaries of SW Spain. Its chronology and vertical evolution allow to differentiate the effects of several pollution episodes (natural, Roman, 19th-20th centuries) on its different sedimentary environments in the last 6 million years. Possible future applications are included in the fields of environmental management or even education.

Summary The input of water from precipitation is one of the most important aspects of a hydrologic model because it controls the basin’s water budget. The model should reproduce the amount and distribution of rainfall in the basin, spatially and temporally. SWAT (Soil and Water Assessment Tool) is one of the most widely used hydrologic models. In this paper the rainfall estimation in SWAT is revised, focusing on the treatment of orographic precipitation. SWAT was applied to the Odiel river basin (SW Spain), with a surface of 2300 km 2 . Results show that SWAT does not reflect reallisticaly the spatial distribution of rainfall in the basin. In relation to orographic precipitation, SWAT estimates the daily precipitation in elevation bands by adding a constant amount to the recorded precipitation in the rain gauge, which depends on the increase in precipitation with altitude and the difference between the mean elevation of each band and the elevation of the recording gauge. This does not reflect rainfall in the subbasin because the increase in precipitation with altitude actually it is not constant, but depends on the amount of rainfall. An alternative methodology to represent the temporal distribution of orographic precipitation is proposed. After simulation, the deviation of runoff volume using the SWAT elevation bands was appreciably higher than that obtained with the proposed methodology.

The Tinto and Odiel rivers in southwest Spain drain the world's largest sulfide mineral formation: the Iberian Pyrite Belt which has been worked since 2,500 BC. The Tinto and Odiel estuarine zones include both an extensive area of salt marsh and an intensively industrialized urban area. As a consequence of pyrite oxidation, the Tinto and Odiel rivers are strongly acidic (pH 3) with unusually high and quite variable metal concentrations. In this study, seasonally varying concentrations of dissolved major and trace elements were determined in the acid mine drainage affected estuary of the Ría de Huelva. During estuarine mixing, ore-derived metal concentrations exhibit excellent correlations with pH as the main controlling parameter. As pH increases, concentrations of dissolved ore-associated elements are attenuated, and this process is enhanced during the summer months. The decrease in Fe and Al concentrations ranged from 80 to 100 % as these elements are converted from dissolved to sediment-associated forms in the estuary. Coprecipitation/adsorption processes also removed between 60 and 90 % of the originally dissolved Co, Cu, Mn, Pb, Zn, and Th; however, Cd and Ni exhibited a greater propensity to remain in solution, with an average removal of approximately 60 %. On the other hand, As and U exhibited a different behavior; it is likely that these elements remain in dissolved forms because of the formation of U carbonates and soluble As species. Concentrations of As remain at elevated levels in the outer estuary (average = 48 μg L(-1)) which exceeds concentrations present in the Tinto River. Nevertheless, the estuary has recently witnessed improvements in water quality, as compared to results of several previous studies reported in the 1990s.

The Tinto River estuary is one of the most contaminated coastal systems in the world due to the high amounts of pollutants this acidic river transports. The tidal influence and the fluvial discharges control the water mixing, which include a salt-induced process (that is typical of all estuaries) and an acid neutralization process (pH-induced mixing). These processes affect the geochemical behavior of uranium, which has a non-conservative pattern. Despite the high concentrations of dissolved uranium in the Tinto River, 234U/238U shows that uranium stems mostly from seawater (between 80 and 100%). Riverine uranium is adsorbed onto both Fe and Al precipitates when the acidic river water is mixed with seawater. Distribution coefficients (Kd) show that dissolved and particulate uranium are controlled by adsorption–desorption processes and the formation of carbonate complexes, both depending on pH. At low pH, uranium tends to be dissolved, and the adsorption by suspended particles is low. As the pH increases, the adsorption processes onto Fe and Al particles are more intense, increasing particulate uranium which reaches a maximum at pH 5.5, where the uranium solubility minimum occurs. At higher pH values, dissolved uranium increases by carbonate complexation.

The Odiel River Basin (SW Spain) drains the central part of the Iberian Pyrite Belt (IPB), a world-class example of sulfide mining district and concomitantly of acid mine drainage (AMD) pollution. The severe AMD pollution and the incipient state of remediation strategies implemented in this region, coupled with the proximity of the deadline for compliance with the European Water Framework Directive (WFD), urge to develop a restoration and water resources management strategy. Furthermore, despite the presence of some reservoirs with acid waters in the Odiel basin, the construction of the Alcolea water reservoir has already started. On the basis of the positive results obtained after more than 10 years of developing a specific passive remediation technology (dispersed alkaline substrate (DAS)) for the highly polluted AMD of this region, a restoration strategy is proposed. The implementation of 13 DAS treatment plants in selected acid discharges along the Odiel and Oraque sub-basins and other restoration measurements of two acidic creeks is proposed as essential to obtain a good water quality in the future Alcolea reservoir. This restoration strategy is also suggested as an economically and environmentally sustainable approach to the extreme metal pollution affecting the waters of the region and could be considered the starting point for the future compliance with the WFD in the Odiel River Basin. © 2016, Springer-Verlag Berlin Heidelberg., This work was supported by the Spanish Ministry of Economic and Competitiveness through the projects EMPATIA (CGL2013-48460-C2-1-R) and SCYRE (CGL2016-78783-C2-1-R) and LIFE-ETAD project (LIFE12 ENV/ES/000250) and partially financed by Program U-INICIA VID 2014, grant 193, University of Chile, and by CONICYT, Program Fondecyt Iniciacion, Project Nº 111500002. R. Pérez-López also thanks the Spanish Ministry of Science and Innovation and the “Ramón y Cajal Subprogramme” (MICINN-RYC 2011). M.A. Caraballo gratefully acknowledges the support from the Advanced Mining Technology Center of the University of Chile. C.R. Cánovas was funded by the European Union’s Seventh Framework Program, Marie Skłodowska-Curie actions, and the Ministry of Economy, Innovation, Science and Employment of the Junta de Andalucía by the program Talent Hub (COFUND-Grant Agreement 291780). We would also like to thank Dr. Philippe Garrigues (editor in chief) and an anonymous reviewer for the support and comments that significantly improved the quality of the original manuscript.

The Iberian Pyrite Belt (IPB) is rich in sulfide deposits which have been intensively exploited, generating a huge problem of contamination of the Odiel River by acid mine drainage (AMD). At its source is a clean river, but along a 7 km-long reach receives five discharges of acid mine waters: Concepción, San Platón, Esperanza, Poderosa and the Agrio River, which drains the AMD contaminated water from the Río Tinto mines. The flows and hydrogeochemical characteristics of these AMD sources have been studied. The Agrio River is the main contributor of acidity, sulfate and metals to the Odiel River due to its high flows and pollutant concentrations. San Platón and Poderosa mines have high sulfate and metal concentrations although both sources are characterized by low or moderate flows while Concepción has the lowest concentrations but higher flows. The composition of AMD sources seem to be controlled by the mineralogy of the deposits and by geochemical processes. Strong seasonal variations are observed for some AMD sources while others are more constant throughout the year., This work was financed by the Spanish Ministry of Economy and Competitiveness through the project EMPATIA (Ref. CGL2013-48460-C2-1-R) and the grant BES-2014-068354.

The Tinto River shows very high concentrations of toxic elements and acidity from its source in the mining area to its mouth. In this paper, we studied the evolution of the levels of toxic elements during part of the Quaternary from the analysis of fluvial deposits that, forming terraces, were originated by the dynamics of the Tinto River. Using a detailed geomorphological cartography, up to nine terrace levels were differentiated in the lower sector of the basin, whose ages range from the Pleistocene to the Holocene. Sampling and geochemical analyses (major elements and trace) were carried out in six of these levels, in addition to sediments of the current flood plain. The results of these analyses do not show any bias from the mid Pleistocene (T8 - Terrace 8) to the early Holocene (T1). Moreover, these geochemical contents are similar to the average values obtained by other authors for the entire South-Portuguese Zone of the Iberian Massif. However, the current sediments of the Tinto River (T0) show a sharp increase in the levels of As, Cu, Pb and Zn compared to the rest, which indicates a serious increment of contamination by toxic elements. Although there are evidences on the existence of a natural process of oxidation of sulfides since the Miocene, the amounts of toxic elements released should be very small compared to those generated since the beginning of the mining activities in the Iberian Pyrite Belt., This research was funded by two Spanish-FEDER projects (AMB99-0226-C03, CGL2010-15810/BTE) and one Research Group of the Andalusia Board RNM-293.

The accurate estimation of metal loads transported by streams is necessary to calculate reliable mass transfers of metals between compartments, both at local and global scales. This estimation is particularly relevant in the case of the Tinto and Odiel Rivers (SW Spain) due to their significant contribution to the total metal transfer from continents to the ocean. At a local scale, the metal load transported by streams plays a key role in predicting the biogeochemical evolution of water reservoirs affected by Acid Mine Drainage (AMD). This work uses the relationships between specific conductivity (SC) and dissolved elements to calculate the metal load of the River Meca, a tributary of the Odiel. The SC and the water level were continuously monitored from April 2009 to June 2010. Water samples were also collected and measurements of the discharge were carried out manually once a month. The relationships between the SC and the concentration of dissolved elements are, in general, very good (R2 > 0.90). However, some key elements such as Fe show a very poor correlation. A simple methodology based on the MIX code (a maximum likelihood method to estimate mixing ratios) was used to elucidate their different behaviours. During the dry period (April–December, 2009) the Fe concentration was lower than that deduced from the SC recorded value due to the precipitation of Fe-oxihydroxides, which also reduced the concentrations of As, Cr, Pb and, to a lesser extent, Cu. At the same time Na, Sr, Ca and Li were enriched because of the higher interaction with the riverbed materials. Correlations between the SC and the metal concentration improved significantly when each period was considered separately. A second dry period (April–June 2010) shows high SC values, although no dissolution/precipitation of solid phases is evidenced. This indicates that SC alone is not enough to predict the dissolved metal loads in Mediterranean AMD streams. The metal load transported by the River Meca was determined for the hydrological year 2009/10 as 1933 ± 129 tonnes of Fe, 990 ± 155 of Al and 378 ± 41 of Zn.