Efecto del resveratrol sobre las funciones cognitivas en adultos mayores: una revisión sistemática y metaanálisis / Effect of resveratrol on cognitive functions in older adults: a systematic review and meta-analysis

Introducción: el resveratrol tiene múltiples efectos beneficiosos en diferentes sistemas del organismo, incluido el nervioso central, sin embargo, los resultados reportados sobre el efecto en las funciones cognitivas en adultos mayores son inconsistentes. Por lo anterior, el propósito de esta revisión sistemática es presentar una síntesis del conocimiento sobre los efectos del resveratrol en las funciones cognitivas en adultos mayores. Método: se llevó a cabo una revisión sistemática acorde con los criterios de PRISMA-2009. La búsqueda de artículos se realizó hasta el 7 de septiembre de 2021 en PubMed, Scopus, Web of Science, PsycINFO, SciELO y TESIUNAM. Las variables de desenlace fueron memoria diferida, inmediata y de trabajo y velocidad del procesamiento. Se estimó la diferencia de medias estandarizadas (DME) para evaluar el efecto. Resultados: se encontraron 1.065 estudios, de los cuales seis cumplieron los criterios de elegibilidad para la revisión sistemática y metaanálisis. No se encontró un efecto significativo en la memoria diferida (DME = 0,69, IC 95 %: 0,85-2,23, p = 0,38), memoria inmediata (DME = 0,56, IC 95 %: -0,20-1,31, p = 0,15), memoria de trabajo (DME = -0,21, IC 95 %: -0,74-0,32, p = 0,43) y velocidad de procesamiento (DME = 0,25, IC 95 %: -0,58-1,07, p = 0,55). Conclusión: nuestros resultados sugieren que el resveratrol no tiene un efecto sobre las funciones cognitivas en adultos mayores. No obstante, es necesario realizar más estudios con diferentes dosis, tipos de formulación del nutracéutico y tiempo de tratamiento. (AU)

Introduction: resveratrol has multiple beneficial effects on different body systems, including the central nervous system, however, the results reported on the effect on cognitive functions in older adults are inconsistent. Therefore, the purpose of this systematic review is to present a synthesis of knowledge about the effect of resveratrol on cognitive functions in older adults. Method: a systematic review was carried out according to the PRISMA-2009 criteria. The search for articles was carried out until September 7, 2021 in PubMed, Scopus, Web of Science, PsycINFO, SciELO, and TESIUNAM. The outcome variables were delayed, immediate, and working memory, and processing speed. The standardized mean difference (SMD) was estimated to assess the effect. Results: one thousand sixty-five studies were found, of which six met the eligibility criteria for the systematic review and meta-analysis. No significant effect was found on delayed memory (SMD = 0.69, 95 % CI: 0.85-2.23, p = 0.38), immediate memory (SMD = 0.56, 95 % CI: -0.20-1.31, p = 0.15), working memory (SMD = -0.21, 95 % CI: -0.74-0.32, p = 0.43) and processing speed (SMD = 0.25, 95 % CI: -0.58-1.07, p = 0.55). Conclusion: our results suggest that resveratrol does not have an effect on cognitive functions in older adults, however, it is necessary to carry out more studies with different doses, type of nutraceutic. (AU)

[Effect of resveratrol on cognitive functions in older adults: a systematic review and meta-analysis]. / Efecto del resveratrol sobre las funciones cognitivas en adultos mayores: una revisión sistemática y metaanálisis.

Introduction: Introduction: resveratrol has multiple beneficial effects on different body systems, including the central nervous system, however, the results reported on the effect on cognitive functions in older adults are inconsistent. Therefore, the purpose of this systematic review is to present a synthesis of knowledge about the effect of resveratrol on cognitive functions in older adults. Method: a systematic review was carried out according to the PRISMA-2009 criteria. The search for articles was carried out until September 7, 2021 in PubMed, Scopus, Web of Science, PsycINFO, SciELO, and TESIUNAM. The outcome variables were delayed, immediate, and working memory, and processing speed. The standardized mean difference (SMD) was estimated to assess the effect. Results: one thousand sixty-five studies were found, of which six met the eligibility criteria for the systematic review and meta-analysis. No significant effect was found on delayed memory (SMD = 0.69, 95 % CI: 0.85-2.23, p = 0.38), immediate memory (SMD = 0.56, 95 % CI: -0.20-1.31, p = 0.15), working memory (SMD = -0.21, 95 % CI: -0.74-0.32, p = 0.43) and processing speed (SMD = 0.25, 95 % CI: -0.58-1.07, p = 0.55). Conclusion: our results suggest that resveratrol does not have an effect on cognitive functions in older adults, however, it is necessary to carry out more studies with different doses, type of nutraceutical formulation and treatment time.

Introducción: Introducción: el resveratrol tiene múltiples efectos beneficiosos en diferentes sistemas del organismo, incluido el nervioso central, sin embargo, los resultados reportados sobre el efecto en las funciones cognitivas en adultos mayores son inconsistentes. Por lo anterior, el propósito de esta revisión sistemática es presentar una síntesis del conocimiento sobre los efectos del resveratrol en las funciones cognitivas en adultos mayores. Método: se llevó a cabo una revisión sistemática acorde con los criterios de PRISMA-2009. La búsqueda de artículos se realizó hasta el 7 de septiembre de 2021 en PubMed, Scopus, Web of Science, PsycINFO, SciELO y TESIUNAM. Las variables de desenlace fueron memoria diferida, inmediata y de trabajo y velocidad del procesamiento. Se estimó la diferencia de medias estandarizadas (DME) para evaluar el efecto. Resultados: se encontraron 1.065 estudios, de los cuales seis cumplieron los criterios de elegibilidad para la revisión sistemática y metaanálisis. No se encontró un efecto significativo en la memoria diferida (DME = 0,69, IC 95 %: 0,85-2,23, p = 0,38), memoria inmediata (DME = 0,56, IC 95 %: -0,20-1,31, p = 0,15), memoria de trabajo (DME = -0,21, IC 95 %: -0,74-0,32, p = 0,43) y velocidad de procesamiento (DME = 0,25, IC 95 %: -0,58-1,07, p = 0,55). Conclusión: nuestros resultados sugieren que el resveratrol no tiene un efecto sobre las funciones cognitivas en adultos mayores. No obstante, es necesario realizar más estudios con diferentes dosis, tipos de formulación del nutracéutico y tiempo de tratamiento.

Wildfire effects on the hydrogeochemistry of a river severely polluted by acid mine drainage.

This study evaluates for the first time the impact of a large wildfire on the hydrogeochemistry of a deeply AMD-affected river at the beginning of the wet season. To accomplish this, a high-resolution water monitoring campaign was performed within the basin coinciding with the first rainfalls after summer. Unlike similar events recorded in AMD-affected areas, where dramatic increases in most dissolved element concentrations, and decreases in pH values are observed as a result of evaporitic salts flushing and the transport of sulfide oxidation products from mine sites, a slight increase in pH values (from 2.32 to 2.88) and decrease in element concentrations (e.g.; Fe: 443 to 205 mg/L; Al: 1805 to 1059 mg/L; sulfate: 22.8 to 13.3 g/L) was observed with the first rainfalls after the fire. The washout of wildfire-ash deposited in the riverbanks and the drainage area, constituted by alkaline mineral phases, seems to have counterbalanced the usual behavior and patterns of the river hydrogeochemistry during autumn. Geochemical results indicate that a preferential dissolution occurs during ash washout (K > Ca > Na), with a quick release of K followed by an intense dissolution of Ca and Na. On the other hand, in unburnt zones parameters and concentrations vary to a lesser extent than burnt areas, being the washout of evaporitic salts the dominant process. With subsequent rainfalls ash plays a minor role on the river hydrochemistry. Elemental ratios (Fe/SO4 and Ca/Mg) and geochemical tracers in both ash (K, Ca and Na) and AMD (S) were used to prove the importance of ash washout as the dominant geochemical process during the study period. Geochemical and mineralogical evidences point to intense schwertmannite precipitation as the main driver of reduction in metal pollution. The results of this study shed light on the response of AMD-polluted rivers to certain climate change effects, since climate models predict an increase in the number and intensity of wildfires and torrential rain events, especially in Mediterranean climates.

Consequences of sea level rise for high metal(loid) loads in the Ría of Huelva estuary sediments.

Ría of Huelva, located in southwestern Spain, is a highly metal(loid)-contaminated estuary system where sediments are exceeding action limits in an increasing order for Cd, Zn, Pb, Cu, and As. With a predicted sea level rise over the next 50 years, the estuary will be subject to flooding with brackish water or seawater. To evaluate the risk of metal(loid) mobilization under future climate scenarios, different locations along the estuary were sampled at different depths. Samples were flooded with river water, brackish water, and seawater under different short- and long-term laboratory setups. Potential metal(loid) mobilization showed that water quality standards for As, Pb, Zn, Ni, Cu, and Cd could be exceeded upon seawater flooding. However, metal(loid) mobilization was not predictable solely based on sediment loads. The driving factors for cation and anion mobility were identified to be mainly pH under low salinity and competitive desorption under high salinity conditions. Further drivers such as wave movement or labile C input in C-limited systems were found to enhance metal(loid) mobilization. Long-term flooding of intact sediment cores revealed that sea level rise will have different effects on the estuary system depending on duration of flooding. Short-term flooding in the near future will first affect alkaline sediments and enhance currently low cation mobilization, while anion mobilization due to reductive Fe dissolution will remain high. Once acidic sediments further inland are flooded with seawater, highest contaminant mobilization can be expected as high salinity will further enhance already high cation mobilization under acidic pH. Long-term flooding with seawater will neutralize the sediment pH and limit cation mobilization compared to acidic pH. However, the contaminant load stored in the estuary is so high that, extrapolating data obtained, mobilization could last for >1000 years, e.g. for As, Pb, and Al.

Potential release and bioaccessibility of metal/loids from mine wastes deposited in historical abandoned sulfide mines.

This study deals with the potential release of metal/loids from sulfide mine wastes upon weathering and the health risks associated with their accidental ingestion. To address this, a complete chemical and mineralogical characterization of a variety of sulfide mine wastes was performed alongside a determination of metal/loid bioaccessibility through leaching tests simulating human digestive and lung fluids. The mine wastes consisted predominantly of Fe (35-55% of Fe2O3) and exhibited high concentrations of trace metalloids such as As (382-4310 mg/kg), Pb (205-15,974 mg/kg), Cu (78-1083 mg/kg), Zn (274-1863 mg/kg), or Sb (520-1816 mg/kg). Most wastes with high concentrations of soluble compounds are considered hazardous according to the European regulations due to the exceedance of threshold values for As, Pb, Cr, Cu, Sb, sulfates, and Zn determined by standardized tests. In general terms, the absorption of waste-hosted metals through both digestive and respiratory routes was low compared to the total metal contents of the wastes, with values below 8% of the total concentration in wastes for most metal/loids including Cu, Zn, As, Cd, Tl, or U. However, some metals exhibited a significantly higher absorption potential, especially through the respiratory route, reaching values of up to 17% for Cr and 75% for Pb, highlighting the strong bioaccessibility of Pb in certain sulfide wastes. Despite the high metal/loid concentrations observed in the studied wastes, a health risk assessment indicated that some non-carcinogenic effects could be observed in children only following the accidental digestion of Pb.

Effects of aluminum incorporation on the schwertmannite structure and surface properties.

Schwertmannite is a common nanomineral in acid sulfate environments such as Acid Mine Drainage (AMD) and Acid Sulfate Soils (ASS). Its high surface area and positively charged surface result in a strong affinity towards toxic oxyanions such as arsenate in solution. However, natural precipitation of schwertmannite also involves the accumulation of other impurities, in particular aluminum, an element that is often incorporated into the structure of Fe-oxide minerals, such as goethite and ferrihydrite, affecting their structural and surface properties. However, little is known about the effect of Al incorporation in schwertmannite on the removal capacity of toxic oxyanions found in AMD and ASS (e.g. arsenate). In this paper, schwertmannite samples with variable Al concentration were synthetized and employed in arsenate adsorption isotherm experiments at a constant pH of 3.5. Solid samples before and after arsenate adsorption were characterized using high energy X-ray diffraction and pair distribution function analyses in order to identify structural differences correlated with the Al content as well as variations in the coordination of arsenate adsorbed on the mineral surface. These analyses showed limited Al accumulation on schwertmannite (up to 5%) with a low effect on its structure. The maximum arsenate sorption capacity (258 mmolH2AsO4 molFe-1) was in the range of that with pure schwertmannite, but a higher proportion of inner-sphere coordination was observed. Finally, Al was found to desorb from schwertmannite, with adsorbed arsenate preventing this effect and increasing the stability of the mineral. These results are useful to interpret observations from the field, in particular from river water affected by AMD and ASS, where similar conditions are observed, and where aluminum incorporation is expected.

Relationship between Arterial Hypertension with Cognitive Performance in Elderly. Systematic Review and Meta-Analysis.

BACKGROUND: Previous systematic reviews report that arterial hypertension (AHT) is associated with lower performance in cognition in the elderly. However, some studies show that with higher blood pressure, a better cognitive performance is obtained. OBJECTIVE: The aim of this study was to determine the relationship between AHT with cognitive performance in the elderly. METHODS: the review involved a search on PubMed, Scopus and PsycINFO databases from January 1990 to March, 2020 to identify the relationship among AHT and cognitive performance in older people. RESULTS: 1170 articles were identified, 136 complete papers were reviewed, a qualitative analysis of 26 studies and a quantitative analysis of eight studies were carried out. It was found that people with AHT have a lower performance in processing speed SMD = 0.40 (95% CI: 0.25, 0.54), working memory SMD = 0.28 (95% CI: 0.15, 0.41) in short-term memory and learning SMD = -0.27 (95% CI: -0.37, -0.17) and delayed recall SMD = -0.20 (95% CI: -0.35, -0.05). Only one study found that higher blood pressure was associated with better memory performance. CONCLUSION: Our results suggest that high blood pressure primarily affects processing speed, working memory, short-term memory and learning and delayed recall.

Prevalencia de probable deterioro cognitivo en adultos mayores de una población mexicana utilizando el MMSE y el MoCA / Prevalence of probable cognitive impairment in older adults of a Mexican population using MMSE and MoCA

Antecedentes: El Mini-Mental State Examination (MMSE) y el Montreal Cognitive Assessment (MoCA) son instrumentos de cribado usados frecuentemente para detectar probable deterioro cognitivo leve (DCL). El MoCA ha mostrado una mayor sensibilidad y especificidad en población clínica que el MMSE. Sin embargo, es posible que en la comunidad se sobreestime la proporción de personas con DCL utilizando el MoCA. Por lo anterior, el objetivo es identificar en adultos mayores de la comunidad, en la ciudad de México, la prevalencia de probable DCL utilizando el MoCA y el MMSE. Método: Se realizó un estudio descriptivo transversal, en una muestra de 231 participantes pertenecientes a grupos comunitarios con una edad entre 55 y 90 años y escolaridad de 0 a 22 años; se aplicó el MMSE y el MoCA. Resultados: Se obtiene una puntuación en MMSE de 25,0 ± 3,1 y en MoCA de 19,8 ± 5,4 con una correlación moderada (r = 0,59, p < 0,05) entre ellos. Un 84% de la población utilizando el MoCA y un 23,8% de la población utilizando el MMSE se clasifican con probable DCL. Conclusión: El MMSE puede dar una estimación más parecida a lo reportado en la literatura que el MoCA en la comunidad. Se discuten las implicaciones en políticas públicas, en el uso clínico y en investigación de una sobreestimación en la proporción de personas con probable DCL (AU)

Background: The Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA) are screening instruments frequently used to detect probable mild cognitive impairment (MCI). The MoCA has shown greater sensitivity and specificity in the clinical population than the MMSE. However, the proportion of people with MCI using the MoCA may be overestimated in the community. Therefore, the objective is to identify in older adults in the community in Mexico City the prevalence of probable DCL using the MoCA and the MMSE. Method: A cross-sectional descriptive study was carried out, in a sample of 231 participants belonging to community groups with an age between 55 and 90 years and schooling from 0 to 22 years; MMSE and MoCA were applied. Results: a score is obtained in MMSE of 25.0 ± 3.1 and in MoCA of 19.8 ± 5.4 with a moderate correlation (r = 0.59, p < 0.05) between them. 84% of the population using MoCA and 23.8% of the population using MMSE are classified as likely MCI. Conclusion: The MMSE can give an estimate more similar to what is reported in the literature than the MoCA in the community. The implications in public policies, in clinical use and in research of an overestimation in the proportion of people with probable MCI are discussed (AU)

Geochemical behaviour and transport of technology critical metals (TCMs) by the Tinto River (SW Spain) to the Atlantic Ocean.

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.

Eco-sustainable passive treatment for mine waters: Full-scale and long-term demonstration.

This paper tries to analyse the technical and economic performance of a full-scale passive Disperse Alkaline Substrate (DAS) treatment plant steadily operating for 28 months (840 days) to treat extremely acidic and metal rich mine waters in the Iberian Pyrite Belt (SW Spain). For the first time, an economic evaluation of this technology and its comparison with other passive treatments is reported. During this period, around 56,000 m3 of mine waters have been treated, without significant clogging or exhaustion of the alkaline substrate. The efficiency of the system is demonstrated by a significant decrease in the average net acidity (from 2005 to -43 mg/L as CaCO3 equivalent) and the total elimination of Al, Cu, REY, Zn, As, Cr, Mo, V, Cd, Pb, Co and other trace metals. Water quality of the treated output discharge meets the threshold values for irrigation and drinking standards, except for Fe, Mn and sulphate. The accumulation of elements of economic interest in the waste (e.g., 32 t of Fe, 6.1 t of Al, 0.8 t of Cu, 0.8 t of Zn, 39.4 kg of REE, 20 kg of Co or 1 kg of Sc), easily extractable with diluted acids, may turn a hazardous waste into a valuable resource. The benefits associated with the revalorization of this metal-rich waste could reach a total of 27478 USD, but is more reliably estimated to be around 8243 USD due to technologic limitations. This benefit would help to defray the maintenance costs (8428 €) and make DAS an economically self-sustainable treatment. The annual treatment cost for DAS was 0.27 €/m3, being the lowest value found among other reported conventional passive schemes, and from 8 to 12 times lower compared to active technologies. The results obtained prove that the DAS technology is the most technically and economically sustainable way to decontaminate acid and metal-rich mine waters in abandoned mines.

Effect of a Mental Stimulation Program of Computer and Internet Learning on Cognitive Functions and Wellbeing in Older Community-Dwelling Mexicans.

BACKGROUND: It has been reported that Mental Stimulation (MS) has a positive effect on cognitive functions and wellbeing. In this sense, different training activities have been proposed for MS such as theater, learning a new language, playing a musical instrument and computing, however, there are few studies on older adults in Latin American countries. For this reason, the purpose of the present study was to determine the effect of a mental stimulation program (MSP) of computer and Internet learning on cognitive functions and wellbeing in older community-dwelling Mexicans. METHOD: A quasi-experimental pilot study was carried out in a convenience sample of 27 adults aged 60 to 69 years, without knowledge of the use of computers and Internet, without chronic non-communicable diseases, depression or cognitive impairment. Two groups were formed: (i) experimental (EG), n = 16 and (ii) control (CG), n = 11. The EG participated in an MSP in which 20 theoretical/practical sessions of two hours each were given, two times a week, on computer and Internet. The CG did not participate in any scheduled activity. All participants were measured before and after the intervention program in processing speed (PS), cognitive inhibition (CI), working and episodicmemory (WM and EM), visuospatial processing (VP), life satisfaction (LS) and positive and negative emotions (PE and NE). RESULTS: After participation in the MSP, the EG showed significantly higher scores on the EM and VP tests compared to the CG (p < 0.05). Conclusions: Our findings suggest that an MSP of computer and Internet learning improves episodicmemory and visuospatial processing in older community-dwelling Mexicans.

Historical roasting of thallium- and arsenic-bearing pyrite: Current Tl pollution in the Riotinto mine area.

Samples of an open-air pyrite roasting heap from the 19th century in the Riotinto mine area (SW Spain) and surrounding sediments and soil along a seasonal surface runoff channel were analyzed to study thallium (Tl) phase transformations during historical roasting of Tl-bearing arsenian pyrite, secondary weathering processes, Tl dispersion and current environmental pollution. Results from Electron Probe Microanalyses (EPMA) indicate an even distribution of Tl in pyrite grains of an ore sample (22 mg kg-1 total Tl), suggesting that Tl is incorporated in the pyrite structure rather than in discrete Tl-sulfide microparticles. The roasting residue (122 mg kg-1 total Tl) consists mainly of hematite. EPMA suggested that Tl in the roasting residue and contaminated soil was co-occurring with Fe oxide particles, with a mean Tl point concentration of 0.12% in samples from the roasting residues. Total concentrations of Tl in soil samples decrease with distance from the roasting heap to 14 mg kg-1. X-ray absorption near-edge structure (XANES) spectra collected on pyrite roasting residue and a soil sample suggest that most Tl is Tl(I) substituting K in jarosite. Sequential extractions show that most Tl (85-99%) in the soil and sediment samples is concentrated in the residual fraction and, thus, is rather strongly bound. Lastly, water extracts indicate that colloidal particles (i.e. <1 µm size) may contribute to the dispersion of Tl around and away from the roasting heaps.

Unraveling the impact of chronic exposure to metal pollution through human gallstones.

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.

Metal fractionation in marine sediments acidified by enrichment of CO2: A risk assessment.

Carbon-capture and storage is considered to be a potential mitigation option for climate change. However, accidental leaks of CO2 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 CO2-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.

Sulfate reduction processes in salt marshes affected by phosphogypsum: Geochemical influences on contaminant mobility.

Sulfate reduction and its associated contaminant immobilization in marsh soils supporting a phosphogypsum stack was examined by pore-water and solid analysis, selective extractions, microscopy and sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy. The negative impact of this stack on estuarine environments is a concerning problem. In the weathering profile, total concentrations of most pollutants increase with depth; instead, dissolved contents in pore-waters increase to middle of the saturated zone but then decrease drastically down to reach the marsh due to sulfide precipitation. Excess of acid-volatile sulfide plus pyritic sulfur over metals bound to the oxidizable fraction indicates that sulfide precipitation is the main mechanism responsible for metal removal in the marsh. Thus, abundant pyrite occurred as framboidal grains, in addition to other minor sulfides of As, Zn and Cu as isolated particles. Moreover, high contents of elemental sulfur were found, which suggest partial sulfide oxidation, but marsh may have capacity to buffer potential release of contaminants. The importance of sulfur species was quantitatively confirmed by XANES, which also supports the accuracy of selective extraction schemes. Accordingly, managing pore-water quality through organic carbon-rich amendments over phosphogypsum stacks could lead to a decrease in contaminant loading of leakages resulting from weathering.

Mobility of rare earth elements, yttrium and scandium from a phosphogypsum stack: Environmental and economic implications.

This paper investigates the mobility and fluxes of REE, Y and Sc under weathering conditions from an anomalously metal-rich phosphogypsum stack in SW Spain. The interactions of the phosphogypsum stack with rainfall and organic matter-rich solutions, simulating the weathering processes observed due to its location on salt-marshes, were simulated by leaching tests (e.g. EN 12457-2 and TCLP). Despite the high concentration of REE, Y and Sc contained in the phosphogypsum stack, their mobility during the leaching tests was very low; <0.66% and 1.8% of the total content of these elements were released during both tests. Chemical and mineralogical evidences suggest that phosphate minerals may act as sources of REE and Y in the phosphogypsum stack while fluoride minerals may act as sinks, controlling their mobility. REE fractionation processes were identified in the phosphogypsum stack; a depletion of LREE in the saturated zone was identified due probably to the dissolution of secondary LREE phosphates previously formed during apatite dissolution in the industrial process. Thus, the vadose zone of the stack would preserve the original REE signature of phosphate rocks. On the other hand, an enrichment of MREE in relation to HREE of edge outflows is observed due to the higher influence of estuarine waters on the leaching process of the phosphogypsum stack. Despite the low mobility of REE, Y and Sc in the phosphogypsum, around 104kg/yr of REE and 40kg/yr of Y and Sc are released from the stack to the estuary, which may imply an environmental concern. The information obtained in this study could be used to optimize extraction methods aimed to recover REE, Y and Sc from phosphogypsum, mitigating the pollution to the environment.

A novel approach for acid mine drainage pollution biomonitoring using rare earth elements bioaccumulated in the freshwater clam Corbicula fluminea.

Lanthanide series have been used as a record of the water-rock interaction and work as a tool for identifying impacts of acid mine drainage (lixiviate residue derived from sulphide oxidation). The application of North-American Shale Composite-normalized rare earth elements patterns to these minority elements allows determining the origin of the contamination. In the current study, geochemical patterns were applied to rare earth elements bioaccumulated in the soft tissue of the freshwater clam Corbicula fluminea after exposure to different acid mine drainage contaminated environments. Results show significant bioaccumulation of rare earth elements in soft tissue of the clam after 14 days of exposure to acid mine drainage contaminated sediment (ΣREE=1.3-8µg/gdw). Furthermore, it was possible to biomonitor different degrees of contamination based on rare earth elements in tissue. The pattern of this type of contamination describes a particular curve characterized by an enrichment in the middle rare earth elements; a homologous pattern (EMREE=0.90) has also been observed when applied NASC normalization in clam tissues. Results of lanthanides found in clams were contrasted with the paucity of toxicity studies, determining risk caused by light rare earth elements in the Odiel River close to the Estuary. The current study purposes the use of clam as an innovative "bio-tool" for the biogeochemical monitoring of pollution inputs that determines the acid mine drainage networks affection.

An anomalous metal-rich phosphogypsum: Characterization and classification according to international regulations.

Phosphogypsum is the main waste generated by the phosphate fertilizer industry. Despite the high level of pollutants found in phosphogypsum and the proximity of stacks to cities, there are no specific regulations for the management of this waste. This study addresses this issue by applying to phosphogypsum, from a fertilizer plant in Huelva (SW Spain), the leaching tests proposed by the current European and US environmental regulations for wastes management and classification. Two main conclusions were obtained: 1) the anomalous metal and metalloid concentrations (e.g. As, Fe, Pb, Sb, Mn, V and Cu) and higher mobility observed in the Huelva phosphogypsum compared to other stacks worldwide, and 2) the discrepancies observed between EU and US regulations dealing with hazardousness classification of these materials. This latter finding suggests the need to use complementary assessment protocols to obtain a better characterization and classification of these wastes. An evaluation of the potential risk to the aquatic life according to the US EPA regulation is proposed in this study. The results warn about the acute and chronic effects on the aquatic life of this waste and suggest the adoption of more strict measures for a safe disposal of phosphogypsum stacks.

Arsenate and Selenate Scavenging by Basaluminite: Insights into the Reactivity of Aluminum Phases in Acid Mine Drainage.

Basaluminite precipitation may play an important role in the behavior of trace elements in water and sediments affected by acid mine drainage and acid sulfate soils. In this study, the affinity of basaluminite and schwertmannite for arsenate and selenate is compared, and the coordination geometries of these oxyanions in both structures are reported. Batch isotherm experiments were conducted to examine the sorption capacity of synthetic schwertmannite and basaluminite and the potential competitive effect of sulfate. In addition, synchrotron-based techniques such as differential pair distribution function (d-PDF) analysis and extended X-ray absorption fine structure (EXAFS) were used to determine the local structure of As(V) and Se(VI) complexes. The results show that oxyanion exchange with structural sulfate was the main mechanism for removal of selenate, whereas arsenate was removed by a combination of surface complexes and oxyanion exchange. The arsenate adsorption capacity of basaluminite was 2 times higher than that of schwertmannite and 3 times higher than that of selenate in both phases. The sulfate:arsenate and sulfate:selenate exchange ratios were 1:2 and 1:1, respectively. High sulfate concentrations in the solutions did not show a competitive effect on arsenate sorption capacity but had a strong impact on selenate uptake, suggesting some kind of specific interaction for arsenate. Both d-PDF and EXAFS results indicated that the bidentate binuclear inner sphere was the most probable type of ligand for arsenate on both phases and for selenate on schwertmannite, whereas selenate forms outer-sphere complexes in the aluminum octahedral interlayer of basaluminite. Overall, these results show a strong affinity of poorly crystalline aluminum phases such as basaluminite for As(V) and Se(VI) oxyanions, with adsorption capacities on the same order of magnitude as those of iron oxides. The results obtained in this study are relevant to the understanding of trace element behavior in environments affected by acid water, potentially opening new research lines focused on remediation by natural attenuation processes or engineered water treatment systems.

Bioavailability and toxicity of metals from a contaminated sediment by acid mine drainage: linking exposure-response relationships of the freshwater bivalve Corbicula fluminea to contaminated sediment.

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.