Pablo Higueras

University of Castilla-La Mancha, Ciudad Real, Castille-La Mancha, Spain

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Publications (58)88.47 Total impact

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    ABSTRACT: Olive trees (Olea europaea, L.) are a very important agricultural resource for Spain in general and for the Castilla-La Mancha region in particular. These trees provide significant amounts of olive oil and olives for direct consumption. In this paper we discuss analytical constraints regarding the uptake of metallic trace elements from soils and other sources for olive-trees growing in the Almadén mercury mining district, the world's largest producer of this element, which is currently inactive. The study was based on the analysis of these metals in soils and sets of olive trees of different ages from seven sites located at different distances from the main mercury sources. The results show good correlations between soil and leaf contents for major elements from the soils (Fe, Al, Mg and Ca), but very little or no relationship between metallic trace elements in soils and leaves. However, bioavailable mercury in the soil does correlate well with leaf contents, indicating a significant uptake of this fraction. Furthermore, detailed analysis of the temporal evolution of mercury contents in leaves compared with the temporal evolution of local atmospheric mercury contents, which decreased dramatically in recent years due to the reclamation of the main dump of the mine, indicates some influence of this parameter on the incorporation of mercury in the leaves and suggests a possible mechanism of atmospheric uptake of the element. Mercury contents in local olive oil and olives are slightly higher for samples taken from areas with also higher mercury concentrations in soils, but levels are well below maximum recommended levels for human food.
    Journal of Geochemical Exploration 02/2014; 123:143–151. · 1.95 Impact Factor
  • EGU General Assembly; 01/2014
  • EGU General Assembly; 01/2014
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    ABSTRACT: Mercury is transported globally in the atmosphere mostly in gaseous elemental form (GEM, [Formula: see text]), but still few worldwide studies taking into account different and contrasted environmental settings are available in a single publication. This work presents and discusses data from Argentina, Bolivia, Bosnia and Herzegovina, Brazil, Chile, China, Croatia, Finland, Italy, Russia, South Africa, Spain, Slovenia and Venezuela. We classified the information in four groups: (1) mining districts where this contaminant poses or has posed a risk for human populations and/or ecosystems; (2) cities, where the concentration of atmospheric mercury could be higher than normal due to the burning of fossil fuels and industrial activities; (3) areas with natural emissions from volcanoes; and (4) pristine areas where no anthropogenic influence was apparent. All the surveys were performed using portable LUMEX RA-915 series atomic absorption spectrometers. The results for cities fall within a low GEM concentration range that rarely exceeds 30 ng m(-3), that is, 6.6 times lower than the restrictive ATSDR threshold (200 ng m(-3)) for chronic exposure to this pollutant. We also observed this behavior in the former mercury mining districts, where few data were above 200 ng m(-3). We noted that high concentrations of GEM are localized phenomena that fade away in short distances. However, this does not imply that they do not pose a risk for those working in close proximity to the source. This is the case of the artisanal gold miners that heat the Au-Hg amalgam to vaporize mercury. In this respect, while GEM can be truly regarded as a hazard, because of possible physical-chemical transformations into other species, it is only under these localized conditions, implying exposure to high GEM concentrations, which it becomes a direct risk for humans.
    Environmental Geochemistry and Health 12/2013; · 2.08 Impact Factor
  • John E. Gray, Michael J. Pribil, Pablo L. Higueras
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    ABSTRACT: Almadén, Spain, is the world's largest mercury (Hg) mining district, which has produced over 250,000 metric tons of Hg representing about 30% of the historical Hg produced worldwide. The objective of this study was to measure Hg isotopic compositions of cinnabar ore, mine waste calcine (retorted ore), elemental Hg (Hg0(L)), and elemental Hg gas (Hg0(g)), to evaluate potential Hg isotopic fractionation. Almadén cinnabar ore δ202Hg varied from − 0.92 to 0.15‰ (mean of − 0.56‰, σ = 0.35‰, n = 7), whereas calcine was isotopically heavier and δ202Hg ranged from − 0.03‰ to 1.01‰ (mean of 0.43‰, σ = 0.44‰, n = 8). The average δ202Hg enrichment of 0.99‰ between cinnabar ore and calcines generated during ore retorting indicated Hg isotopic mass dependent fractionation (MDF). Mass independent fractionation (MIF) was not observed in any of the samples in this study. Laboratory retorting experiments of cinnabar also were carried out to evaluate Hg isotopic fractionation of products generated during retorting such as calcine, Hg0(L), and Hg0(g). Calcine and Hg0(L) generated during these retorting experiments showed an enrichment in δ202Hg of as much as 1.90‰ and 0.67‰, respectively, compared to the original cinnabar ore. The δ202Hg for Hg0(g) generated during the retorting experiments was as much as 1.16‰ isotopically lighter compared to cinnabar, thus, when cinnabar ore was roasted, the resultant calcines formed were isotopically heavier, whereas the Hg0(g) generated was isotopically lighter in Hg isotopes.
    Chemical Geology 10/2013; 357(October):150-157. · 3.15 Impact Factor
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    ABSTRACT: One strain of Bradyrhizobium canariense (L-7AH) was selected for its metal-resistance and ability to nodulate white lupin (Lupinus albus L.) plants, from a collection of rhizobial strains previously created from soils of the Almadén mining district (Spain) with varying levels of Hg contamination. Plants were inoculated with either strain L-7AH (Hg-tolerant) or L-3 (Hg-sensitive, used as control), and watered with nutrient solutions supplemented with various concentrations (0-200 μM) of HgCl2 in a growth chamber. L. albus inoculated with L-7AH were able to nodulate even at the highest concentration of Hg while those inoculated with L-3 had virtually no nodules at Hg concentrations above 25 μM. Plants inoculated with L-7AH, but not those with the control strain, were able to accumulate large amounts of Hg in their roots and nodules. Nodulation with L-7AH allowed plants to maintain constant levels of both chlorophylls and carotenoids in their leaves and a high photosynthetic efficiency, whereas in those inoculated with L-3 both pigment content and photosynthetic efficiency decreased significantly as Hg concentration increased. Nitrogenase activity of plants nodulated with L-7AH remained fairly constant at all concentrations of Hg used. Results suggest that this symbiotic pair may be used for rhizoremediation of Hg-contaminated soils.
    Plant Physiology and Biochemistry 10/2013; 73C:168-175. · 2.78 Impact Factor
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    ABSTRACT: The giant Almadén mercury deposit (Spain) is hosted by the Lower Silurian Criadero Quartzite; in turn this ore-bearing rock unit is cross-cut by the so-called Frailesca unit, a diatreme body of basaltic composition. The geochemical characteristics of the Silurian to Devonian Almadén District volcanic units indicate that these rocks originated from an enriched, evolving mantle source that ultimately yielded basanites–nephelinites to rhyolites, through olivine-basalts, pyroxene-basalts, trachybasalts, trachytes, very scarce rhyolites, and quartz-diabases. The Silurian intraplate alkaline volcanism developed in submarine conditions which triggered widespread hydrothermal activity resulting in Hg ore formation and pervasive alteration to carbonates. The δ18O, δ13C, and δ34S isotopic signatures for carbonates and pyrite suggest different sources for carbon and sulfur, including magmatic and organic for the former and magmatic and sea water for the latter. The most important and efficient natural source of mercury on Earth is by far the volcanic activity, which liberates mercury via quiescent degassing and catastrophic (Plinian) events when eruptions can overwhelm the atmospheric budget of Hg. Thus, we suggest that CO2 degasification and coeval distillation of mercury from the volcanic rocks fed the huge hydrothermal system that led to massive deposition of mercury at Almadén. Build up of Hg0gas in magmatic chambers during waning rifting in the Late Ordovician, followed by renewed volcanism in the Early Silurian, would have resulted in massive degasification of the accumulated mercury. Part of this mercury went into the Criadero Quartzite leading to formation of the huge Almadén deposit and others (e.g., El Entredicho) along the same stratigraphic level. Progressive depletion of the deep seated magmatic Hg stock would have resulted in a drastic reduction in ore deposit size after the Lower Silurian when smaller deposits formed (e.g., Las Cuevas).
    Ore Geology Reviews 10/2013; 51:93–102. · 2.42 Impact Factor
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    International Conference on Mercury as a Global Pollutant (ICMGP 2013), Edimburgh; 07/2013
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    ABSTRACT: Mercury emissions from soil samples with different mercury contents have been estimated using a closed circuit array. The samples were collected from the Almadén mercury mining district. The emissions confirmed that temperature and light radiation favour mercury desorption due to the increase in the mercury vapour pressure. An additional positive factor could be the photocatalytic reduction of soluble Hg2+ to volatile Hg0 at the soil surface. A physicochemical model based on mass transfer and equilibrium was developed and was used to reproduce the mercury emissions at the laboratory scale. The use of this model allowed us to obtain the unknown mass transfer coefficient (KL) and adsorption parameters required to quantify the possible gaseous mercury fluxes from these contaminated soils. Experimental results indicate that an equilibrium between the solid and gas phases was established. The proposed kinetic model reproduced perfectly the experimental data, with KL found to be proportional to the inverse of temperature and independent of the radiation. The concentration of mercury in the gas phase was mainly dependent on the soluble mercury content (HgS). Equilibrium data were fitted by Langmuir and Freundlich models and the best fit was obtained using the multi-layer model attending to the convex shape of the curves, which is characteristic of non-porous or possibly macroporous materials having a low adsorption energy. The Freundlich constant (KF) was also fitted as a polynomial function with temperature and this gave a straight line for the light radiation and a second grade equation for dark conditions. Once the parameters had been obtained, the Hg emission fluxes from contaminated soils were estimated and the values were between two and three orders of magnitude higher than those published in the literature for non-contaminated soils.
    Analytical methods 05/2013; 5(11):2793-2801. · 1.86 Impact Factor
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    ABSTRACT: Regional soil geochemistry in the Ojailén Valley: a realm dominated by the industrial and mining city of Puertollano (South Central Spain). Authors: Miguel A. López-Berdonces¹; Sergio Fernández Calderón¹; Pablo Higueras¹; José María Esbrí¹; Beatriz González-Corrochano¹; Eva Mª García-Noguero¹; Alba Martínez-Coronado¹; Carolina García Noguero¹ ¹Instituto de Geología Aplicada, Universidad de Castilla La Mancha, Almadén 13400 (Spain). Ojailén Valley is situated in South Central of Spain, an area where livestock, agriculture, mining and industry coexist. This work tries to assess the relationships between these activities and local environmental compartments: water, soils and heavy metal contents, and establish the most appropriate methodology of sample treatment and analytical techniques that can be employed on this kind of studies. For soil geochemistry, 152 samples were taken at two different depths, one at surface layer and another at 20 cm depth, and establish relationships between them and the possible sources. For this purpose, we determine soil parameters (pH, conductivity and organic matter) and total metal contents by Energy Dispersion of X Ray Fluorescence (EDXRF). Samples with higher nickel contents were analyzed with Inductive Coupled Plasma Spectroscopy (ICP-OES) after acid digestion. The study of surface waters includes 18 samples along the river and tributaries near mining and industrial areas. Water analysis was performed by ICP-OES. Soil samples shows pH between 6 and 8.5, highest located near on the east part of the valley, in the vicinity of petrochemical complex. Conductivity values show higher levels (1600 µS cm¯¹) in the vicinity of Puertollano and the industrial sites. Local reference value (LRV) for contaminated soils were determined according to the methodology proposed by Jimenez-Ballesta et al. (2010), using the equation: LRV=GM + 2SD, where LRV: Local Reference Value, GM: Geometric Mean, SD: Standard Deviation. Trace metals values are significantly higher than calculated LRV, especially for Zn, Pb, (Average content: 230 mg kg¯¹ and 249.9 mg kg¯¹ respectively), probable due to Pb-Zn mining in the nearest Alcudia valley. Other elements seem to be influenced by petrochemical industry (Ni, V, and Cu) with LRV: 199.9 mg kg¯¹, 39.2 mg kg¯¹ and 184.2 mg kg¯¹ respectively. Most water samples have metal contents higher than levels for drinking water (WHO, 2006), especially Fe and Pb with 20 µg l¯¹ and 10 µg l¯¹ respectively. Higher metal contents were located on three different sites: downstream an open-pit coal mine, in stagnant water where we can find an old sewage treatment plant, and downstream a photovoltaic plant built in 2008. We can consider that Ojailén Valley is not an area with high contents in heavy metals in the environment, but Puertollano and its petrochemical complex have contents in Pb, Zn, Cu, As, Ni above the LRV. A comparison of results obtained by ICP-MS and XRF related to Pb, Zn, Cr, Ni in thirty-four selected samples, we can conclude that both techniques are qualitatively agree, although XRF cannot be considered suitable for establishing reference legal limits. References Jiménez-Ballesta, R; Conde-Bueno,P; Martin-Rubí,J.A.; García-Jímenez,R. 2010. Geochemical baseline contents levels and soil quality reference values of trace elements in soils from the Mediterranean (Castilla-La Mancha, Spain). Central European Journal of Geosciences 2, 441-454. WHO2006. Guidelines for drinking- water quality, Vol.1, 3rd edition incorporating 1st and 2nd addenda. (http//www.who.int/entity/water_sanitation_health/dwq/fulltext.pdf) Geneve, Suiza.
    04/2013;
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    ABSTRACT: Soil-plant transfer of heavy metals in Pb-Zn mining sites from Alcudia Valley (South Spain). Authors: Miguel A. López-Berdonces¹; Pablo Higueras¹; Jose María Esbrí¹; Beatriz González-Corrochano¹; Eva Mª García- Noguero¹; Alba Martínez Coronado¹; Sergio Fernández-Calderón¹; Carolina García-Noguero¹ ¹Instituto de Geología Aplicada, Universidad Castilla la Mancha, Pza. Manuel Meca, 1. 13400 Almadén, Spain. Alcudia Valley is a vast territory recently declared Natural Park, located in South of Spain. It is an area rich in mineral deposits of Zn and Pb and mining exists since the first millennium BC., having its highest ore production between mid-nineteenth century and the middle of the twentieth. This area has been selected because has more than 120 abandoned mines without remediation actions, with dumps and tailings with high contents of zinc and lead sulfides, and Cu, Ag, Cd, As, Sb in minor concentrations. In this study we determinate the transfer rate of these metals from soils to plants represented by oak leaves (Quercus ilex), because this specie is common within the selected area. To evaluate the soil-plant transfer were studied the correlation of contents, total and extractable, in soil-leaves. Extractable fraction was done by for different methods in water, EPA 1312 sulfuric acid: nitric acid 60:40 v., Ammonium Acetate and EDTA. To establish the correlation between heavy metals from soils to plants is necessary to know the contents of these and bioavailable content in soil. Three areas (S. Quintín, Romanilla, Bombita) were selected, taking 24 samples of soils and leaves. Analyzed leaves by XRF showed that Mn, Pb, Zn and Mo in S.Quintin and Romanilla, Mn, Pb in Bombita, exceeded the toxicity threshold. The same samples analyzed by ICP show us the toxicity threshold is exceeded Pb, Zn and Hg in S.Quintin, and Pb in Romanilla. The heavy metal content in leaves compared between two techniques analytical gives an acceptable correlation Zn - Pb with R²= 95. Total metal contents in soils were analyzed by EDXRF (Energy Dispersion X Ray Fluorescence). We obtained RRL (Regional Reference Level), from La Bienvenida soil samples with values 20 Ni; 53 Cr; 38 Cu; 125 Zn; 128 Pb; 26 As, all in mg kg¯¹. Taking into account the values obtained in S.Quintin Pb 10127; Zn 2861; As 183; Cd 138; Cu 331; Ni 60 and Hg 893 mg kg¯¹, we can say that S.Quintin is a highly contaminated area; Bombita and Romanilla we would consider polluted areas where only Ni, As have values below RRL. We found differences in uptake patterns on the three areas due to heterogeneity in soil parameters and acid drainage, especially in S.Quintín mine where only measured uptake of Sb by plant has a good linear correlation with metal content extract with Ammonium Acetate. Romanilla has more homogeneous soil condition where we found an high soil-plant correlation Ag, As, Cd, Zn using EDTA and Acetate. Bombita has a similar characteristics, with high correlations between plants contents and soil in Cd, Cu, Pb, Zn with EDTA and Acetate. Total contents of heavy metal in a soil is not enough to evaluate the Toxicity Potential, it is necessary to know the bioavailable fraction present in the soil and the extractable fraction which proved to be the decisive factor in the content of heavy metal in plant of studied areas; the correlation in metals content soil-plant is higher in extractable content metals than in total content.
    04/2013;
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    ABSTRACT: Human activities, as mining, can alter the concentrations of metals in the environmental compartments and facilitate their dispersion (Moreno Grau, 2003). Total concentrations are usually evaluated, but they do not provide information about the bioavailability and toxicity of metals, since changes in the environmental conditions cause selective release of the total metal content (Sahuquillo et al., 2003). Thus, the bioavailability or toxic effects of the metals can only be studied by determining their chemical partitioning (Quevauviller, 1998). Leaching by selective chemical extracts is the conventional method for evaluating the availability of elements. The Mazarambroz Pb-Zn mine, located in the Castilla-La Mancha region (central Spain), is an important case of abandoned Pb-Zn sulphide mine, with high concentrations of other highly toxic heavy metals such as Cu, As and Cd. The objectives of this work were to determine the extent of the heavy metal contamination and to study the heavy metal bioavailability, by the application of selective chemical extractions, in the Mazarambroz mine area. Soil and sediment samples were taken from the studied area according to a systematic sampling type (regular grid). Soil main parameters (reactivity and conductivity) were determined. Chemical extractions were made using two different selective reagents: i) CaCl2 (0.01M) (Novozamsky et al., 1993) and; ii) EDTA (0.05 M) (Quevauviller, 1996). The contents of heavy metals in the extracts were measured by inductively coupled plasma-mass spectroscopy (ICP-MS). The compounds extracted with the CaCl2 solution represent the water soluble and exchangeable fractions, so they can be considered as the metal concentration that can be absorbed by plants. EDTA solution extracts metals on exchange sites of both inorganic and organic complexes. Additionally, it can dissolve calcareous materials through complexation of calcium and magnesium (Chao, 1984; Sahuquillo et al., 2003). Total geochemical analyses of the samples were carried out using a Field Portable X-Ray Fluorescence Spectroscopy analyser (EDXRF). Results were statistically processed with Minitab 15.0 and mapped with Surfer 9. The mean concentrations of the studied heavy metals are significantly higher than the world average, the Castilla-La Mancha region mean and the local reference value for soils, so the studied area can be considered a polluted area as consequence of the mining process carried out in the Mazarambroz Pb-Zn mine. The total affected area by high concentrations of heavy metals differs depending on the studied element, reaching the maximum extension and importance for lead and zinc. In the studied area, soil and sediments are also affected by very low pH and high conductivity, which indicates the presence of soluble salts, likely sulfates, products of the sulfide oxidation. These results would imply an increase in the heavy metal mobility and transference to the plants and, as a consequence, an increase in the environmental damage since the area close to the mine is used for the cultivation of cereals and rabbit hutting. The results of the extractions show that the highest extracted concentrations are obtained from the sediment samples due to the influence of the stream in the weathering of this type of materials. References - Chao, T.T., 1984. Use of partial dissolution techniques in geochemical exploration. Journal of Geochemical Exploration, 20, 101-135. - Moreno Grau, M.D., 2003. Environmental Toxicology: Risk Assessment to Human Health. Mc Graw Hill, Madrid. - Novozamsky, I., Lexmond, T.M., Houba, V.J.G., 1993. A single extraction procedure of soil for evaluation of uptake f some heavy metals by plants. International Journal of Environmental Analytical Chemistry, 51, 47-58. - Quevauviller, P., Lachica, M., Barahona, E., Rauret, G., Ure, A., Gomez, A., Muntau, H., 1996. Interlaboratory comparison of EDTA and DTPA procedures prior to certification of extractable trace elements in calcareous soil. Science of the Total Environment, 178, 137-132. - Quevauviller, Ph., 1998. Operationally defined extraction procedures for soil and sediment analysis I. Standardization. Trac-Trends in Analytical Chemistry, 17 (5), 289-298. - Sahuquillo, A., Rigol, A., Rauret, G., 2003. Overview of the use of leaching/extraction tests for risk assessment of trace metals in contaminated soils and sediments. Trac-Trends in Analytical Chemistry, 22 (3), 152-159.
    Journal of Geochemical Exploration. 04/2013;
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    ABSTRACT: The Mt. Amiata volcano is the youngest and largest volcanic edifice in Tuscany (central-northern Italy) and is characterized by a geothermal field, exploited for the production of electrical energy. In the past Mt. Amiata was also known as a world-class Hg district whose mining activity was mainly distributed in the central-eastern part of this silicic volcanic complex, and particularly in the municipality of Abbadia San Salvatore. In the present work we report a geochemical survey on Hg 0 measurements related to the former mercury mine facilities prior the reclamation project. The Hg 0 measurements were carried out by car for long distance regional surveys, and on foot for local scale surveys by using two LUMEX (915þ and M) devices. This study presents the very first Hg 0 data obtained with this analytical technique in the Mt. Amiata area. The facilities related to the mining areas and structures where cinnabar was converted to metallic Hg are characterized by high Hg values (4 50,000 ng m À 3), although the urban center of Abbadia San Salvatore, few hundred meters away, does not appear to be receiving significant pollution from the calcine area and former industrial edifices, all the recorded values being below the values recommended by the issuing Tuscany Region authorities (300 ng m À 3) and in some cases approaching the Hg background levels (3–5 ng m À 3) for the Mt. Amiata area.
    Environmental Research 03/2013; 125:179–187. · 3.24 Impact Factor
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    ABSTRACT: Two events during the last decade had major environmental repercussions in Almadén town (Spain). First it was the ceasing of activities in the mercury mine and metallurgical facilities in 2003, and then the finalization of the restoration works on the main waste dump in 2008. The combination of both events brought about a dramatic drop in the emissions of gaseous elemental mercury (GEM) to the atmosphere. Although no one would now call the Almadén area as 'mercury-free', the GEM levels have fallen beneath international reference safety levels for the first time in centuries. This has been a major breakthrough because in less than one decade the site went from GEM levels in the order of "tens of thousands" to mere "tens" nanogram per cubic meter. Although these figures are per se a remarkable achievement, they do not mark the end of the environmental concerns in the Almadén district. Two other sites remain as potential environmental hazards. (1) The Las Cuevas mercury storage complex, a partially restored ex-mining site where liquid mercury is being stored. The MERSADE Project (LIFE-European Union) has tested the Las Cuevas complex as a potential site for the installation of a future European prototype safe deposit of surplus mercury from industrial activities. Despite restoration works carried out in 2004, the Las Cuevas complex can still be regarded as hotspot of mercury contamination, with high concentrations above 800μgg-1 Hgsoil and 300ngm-3 Hggas. However, as predicted by air contamination modeling using the ISC-AERMOD software, GEM concentrations fade away in a short distance following the formation of a NW-SE oriented narrow plume extending for a few hundred meters from the complex perimeter. (2) Far more dangerous from the human health perspective is the Almadenejos area, hosting the small Almadenejos village, the so-called Cerco de Almadenejos (CDA; an old metallurgical precinct), and the mines of La Nueva Concepción, La Vieja Concepción and El Entredicho. The CDA is an old metallurgical site that operated between 1794 and 1861, leaving behind a legacy of extremely contaminated soils (mean concentration=4220μgg-1 Hg) and GEM emissions that in summer can reach levels up to 4,000-5,000ngm-3. Thus the CDA remains the sole 'urban' site in the district surpassing GEM international reference safety levels. In order to prevent these emissions, the CDA requires immediate action regarding restoration works. These could involve the full removal of soils or their permanent capping to create an impermeable barrier.
    Environmental Research 03/2013; · 3.24 Impact Factor
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    ABSTRACT: A survey of symbiotic bacteria from legumes grown in high mercury-contaminated soils (Almadén, Spain) was performed to produce a collection of rhizobia which could be well adapted to the environmental conditions of this region and be used for restoration practices. Nineteen Hg-tolerant rhizobia were isolated from nodules of 11 legume species (of the genera Medicago, Trifolium, Vicia, Lupinus, Phaseolus, and Retama) and characterized. Based on their growth on Hg-supplemented media, the isolates were classified into three susceptibility groups. The minimum inhibitory concentrations (MICs) and the effective concentrations that produce 50% mortality identified the patterns of mercury tolerance and showed that 15 isolates were tolerant. The dynamics of cell growth during incubation with mercury showed that five isolates were unaffected by exposure to Hg concentrations under the MICs. Genetic analyses of the 16S rRNA gene assigned ten strains to Rhizobium leguminosarum, six to Ensifer medicae, two to Bradyrhizobium canariense, and one to Rhizobium radiobacter. Inoculation of host plants and analysis of the nodC genes revealed that most of them were symbiotically effective. Finally, three isolates were selected for bioremediation processes with restoration purposes on the basis of their levels of Hg tolerance, their response to high concentrations of this heavy metal, and their genetic affiliation and nodulation capacity.
    Applied Microbiology and Biotechnology 01/2012; 96(2):543-54. · 3.69 Impact Factor
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    ABSTRACT: Potosí (South West Bolivia) is a well known historical mining site in the world, with mining activity centered at the so-called Cerro Rico. It is an impressive mount formed by rhyolitic rocks affected by intensive hydrothermal alteration, and hosting a complex vein deposit including mainly Ag and Sn minerals. From the start of the mining activity, in the late 16th century, to 1850, the main ore was silver minerals, and from 1850 the silver ores exhausted, and mining activity centered on tin minerals. During the first stage, the silver minerals were treated by amalgamation, using the so-called “método de patio”, which implied the usage of mercury and other compounds as metallurgical agents, and supposed the release of important quantities of mercury to the local environment. This work was carried out at the “ingenios”, milling and mercury processing facilities located next to streams, in order to have the water and mechanical energy needed for the process, and nowadays in ruins. Our results put forward very low mercury vapor concentrations in the region, reaching only occasionally values over 4ng m−3, as well as in the town area, were maximum values reach 31ng m−3 with an average of 5.5ng m−3; detailed surveys at the “Ingenios” demonstrated that in these facilities mercury vapor concentrations were also low, but the excavation of the topsoil causes an important release of the elemental vapor, reaching concentrations over 3000ng m−3. Causes of this low emission of unmodified soil are here interpreted as caused by biological and physicochemical transformation of the metallic mercury accumulated in the soil, to mineral phases such as cinnabar/metacinnabar and/or schuetteite, in reactions mediated by the formation of methylmercury.
    Fuel and Energy Abstracts 01/2012;
  • De Re Metallica. 01/2012; 19:53-65.
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    ABSTRACT: The laboratory flux measurement system (LFMS) and dispersion models were used to investigate the kinetics of mercury emission flux (MEF) from contaminated soils. Representative soil samples with respect to total Hg concentration (26-9770 μg g(-1)) surrounding a decommissioned mercury-mining area (Las Cuevas Mine), and a former mercury smelter (Cerco Metalúrgico de Almadenejos), in the Almadén mercury mining district (South Central Spain), were collected. Altogether, 14 samples were analyzed to determine the variation in mercury emission flux (MEF) versus distance from the sources, regulating two major environmental parameters comprising soil temperature and solar radiation. In addition, the fraction of the water-soluble mercury in these samples was determined in order to assess how MEF from soil is related to the mercury in the aqueous soil phase. Measured MEFs ranged from less than 140 to over 10,000 ng m(-2) h(-1), with the highest emissions from contaminated soils adjacent to point sources. A significant decrease of MEF was then observed with increasing distance from these sites. Strong positive effects of both temperature and solar radiation on MEF was observed. Moreover, MEF was found to occur more easily in soils with higher proportions of soluble mercury compared to soils where cinnabar prevails. Based on the calculated Hg emission rates and with the support of geographical information system (GIS) tools and ISC AERMOD software, dispersion models for atmospheric mercury were implemented. In this way, the gaseous mercury plume generated by the soil-originated emissions at different seasons was modeled. Modeling efforts revealed that much higher emissions and larger mercury plumes are generated in dry and warm periods (summer), while the plume is smaller and associated with lower concentrations of atmospheric mercury during colder periods with higher wind activity (fall). Based on the calculated emissions and the model implementation, yearly emissions from the "Cerco Metalúrgico de Almadenejos" decommissioned metallurgical precinct were estimated at 16.4 kg Hg y(-1), with significant differences between seasons.
    Journal of Environmental Monitoring 12/2011; 13(12):3460-8. · 2.09 Impact Factor
  • 09/2011: pages 619 - 624; , ISBN: 978-989-8196-16-3
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    ABSTRACT: Mercury exposure of the local population was assessed in two areas of the Almadén mercury mining district, Spain, which has been the world's largest producer of this element. Two groups, who are exposed to different sources of mercury, from a point source in Almadén and a diffuse source hundreds of kilometres away in the same region, were studied. Total mercury (THg) in human hair ranged from 0.20 to 9.35 mg kg(-1) and the mean value was 2.64 mg kg(-1). About 87% of subjects had THg levels in excess of the EPA reference dose (RfD=1.0 mg kg(-1)), while a high percentage (68%) of them live in Almadén. There was a clear increase in hair Hg with reported fish consumption and the highest mean hair mercury level was 4 times the RfD in a group who had reported the highest consumption of fish. For the whole group, there was a significant effect of age, gender and fish consumption in relation to Hg concentration in the hair. Nevertheless, when both groups were tested separately by means of a multivariate regression model, there was significant exposure in those living near the mine area. Several factors such as age, gender and fish consumption remained statistically significant and were associated with THg. The main conclusion is that people living close to the hot spot are more impacted by mercury than people living further away. The intake of Hg through consumption of fish is an important parameter for Hg exposure; however, in the case of people living close to the hot spot, their levels are related to the highly Hg-impacted living environment.
    Chemosphere 04/2011; 84(5):571-7. · 3.14 Impact Factor

Publication Stats

346 Citations
88.47 Total Impact Points

Institutions

  • 1132–2014
    • University of Castilla-La Mancha
      • • Instituto de Geología Aplicada (IGeA)
      • • Geological and Mining Engineering
      Ciudad Real, Castille-La Mancha, Spain
  • 2005–2007
    • Escola Universitària Politècnica
      Almadén, Castille-La Mancha, Spain
  • 2006
    • Complutense University of Madrid
      • Facultad de Farmacia
      Madrid, Madrid, Spain