Sustainable Application of Waste Sludges from the Wastewater Treatment Plant Generated during the Production of Heating Devices in the Construction Industry.

This research presented, for the first time, the results of the successful application of the waste press sludges, WSLP (plant for lacquer and paint) and WSEP (powdery enamel plant), from a wastewater treatment plant generated during heating device production in the construction industry. The results of WSEP characterization and its influence on cement paste, mortar, and concrete properties showed that this material could be used as a cement replacement (with a maximum replacement amount of 20%) in producing mortar and concrete. Although waste WSLP sludge does not possess pozzolanic properties and does not meet the criteria prescribed by the standards for application in mortar and concrete due to its chemical inertness and fineness, as well as its extended setting time, it can be used as a replacement for stone filler or other powdered mineral admixture in the production of self-compacting concrete (SCC) in amounts up to 100%, with a maximum quantity of up to 100 kg/m3. The obtained results indicate that with the appropriate conversion, waste sludges, despite representing hazardous waste, can be used as safe products in the construction industry; i.e., the waste material can become a useful and valuable raw material by applying (respecting) all of the principles of the green economy.

Concentration, Propagation and Dilution of Toxic Gases in Underground Excavations under Different Ventilation Modes.

The drill-and-blast method is widely used for the excavation of hard rock tunnels. Toxic gases such as carbon monoxide and nitrogen oxides are released immediately after blasting by the detonation of explosives. To provide a safe working environment, the concentration of noxious gases must be reduced below the threshold limit value according to health and safety regulations. In this paper, one-dimensional mathematical models and three-dimensional CFD numerical simulations were conducted to analyze the concentration, propagation and dilution of the blasting fumes under different operating conditions. Forced, exhaust and mixed ventilation modes were compared to determine the safe re-entry times after blasting in a 200 m-long tunnel excavated using the top-heading-and-benching method. Based on the numerical simulations, carbon monoxide was the most critical gas, as it required a longer ventilation time to reduce its concentration below the threshold limit value. The safe re-entry time reached 480 s under the typical forced ventilation mode, but was reduced to 155 s when a mixed ventilation system was used after blasting, reducing the operating costs. The reduction of the re-entry time represents a significant improvement in the excavation cycle. In addition, the results obtained show that 1D models can be used to preliminary analyze the migration of toxic gases. However, to reliably determine the safe re-entry times, 3D numerical models should be developed. Finally, to verify the accuracy of the CFD results, field measurements were carried out in a railway tunnel using gas sensors. In general, good agreements were obtained between the 3D numerical simulations and the measured values.

Mine Water for the Generation and Storage of Renewable Energy: A Hybrid Hydro-Wind System.

Mine water is normally considered as waste that has to be managed. However, new applications are increasingly being sought for the water that floods mining voids, especially in relation to its use as an energy resource. The worldwide energy market, within the current transition framework, is searching for creative approaches to produce and store clean energy. In particular, underground pumped hydroelectric energy storage systems (UPHS) constitute efficient and flexible alternatives to deal with intermittent renewable energy sources. In this work, a UPHS is designed using the mine water and the voids of a closed coal mine in Asturias (North-west Spain) as a lower reservoir. Moreover, this system is combined with a wind energy generation facility and the efficiency of the hybrid system is evaluated. With an investment cost of EUR 193 M, a 40 MW UPHES joined to a 60 MW wind farm would generate benefits of about EUR 54 M in 40 years. The reduction in CO2 emissions (29,000 equivalent tons per year) and the social benefits in a traditional mining area are other intangible advantages of this system.

Mercury and arsenic mobility in resuspended contaminated estuarine sediments (Asturias, Spain): A laboratory-based study.

Estuarine sediments must be dredged to allow for navigation, and where these sediments are placed after dredging depends upon guidelines based only on the total concentration of contaminants. However, resuspension events could seriously affect the mobility and speciation of contaminants, including potentially toxic trace elements stored in sediments. The effects of resuspension on the cycling of mercury (Hg) and arsenic (As) between the sediment and water column was investigated in a mesocosm study. Four experiments were conducted in three estuaries in northern Spain based on samples collected from sites which have been impacted by decommissioned Hg and As mines and periodically subjected to dredging activities. Designed to mimic the resuspension of particles, each of the experiments revealed that the release of Hg and As species does not only depend on the total concentration in the sediments (16.3-50.9 mg kg-1, for As and 0.52-5.01 mg kg-1 for Hg). The contribution from porewaters and the subsequent reductive dissolution and/or desorption appear to be the main processes responsible for the abrupt increase in dissolved Hg and As species (maximum release of 427% and 125%, respectively). In some cases, As and Hg continued to remain at high concentrations in the water column even after the experiments were completed, thus testifying to their critical persistence in the dissolved form. Conversely, at the other sites, the restoration of pre-resuspension conditions was observed only a few hours after resuspension, mainly due to the role of Fe oxy-hydroxides which provides suitable surfaces for adsorption and/or co-precipitation involving dissolved Hg (maximum removal of -58%) and As (maximum removal of -25%) species. The results of this research could be helpful to take appropriate decisions regarding dredging especially at the Nalòn estuary, where the release of dissolved As(V) and MeHg appeared to be favoured by sediment resuspension.

Geochemical distribution of selected heavy metals in the Asturian coastline sediments (North of Spain).

Sediments from 35 beaches along the Asturian coastline in the north of Spain were studied. Geochemical analyses were conducted to assess the distribution of metal(oid) concentrations on the coast. Samples were correlated by a cluster analysis based on their geochemical concentrations, showing three different groups. Group 1 and Group 2 were composed of the samples of the occidental and oriental beaches, respectively, while Group 3 was formed by the beaches that are in the area of influence of one of the main harbours in the north of Spain where there is an established metal and chemical industry. These associations may explain the origin of the metal concentrations in the coastline. Both geological and anthropic sources generated geochemical anomalies in the sediment concentrations that sometimes surpassed quality OSPAR criterion.

Historical accumulation of potentially toxic trace elements resulting from mining activities in estuarine salt marshes sediments of the Asturias coastline (northern Spain).

The extensive extraction activity of mercury ores in Asturias (northwest Spain), also rich in As and Sb, has impacted the Nalón river estuary. The objective of this research was to assess the historical evolution of As-Hg-Sb accumulation in the salt marsh sediments of this area. For this purpose, sediment cores were collected from two different salt marshes (eastern and western river banks) in the estuarine environment to evaluate the degree of anthropogenic enrichment and the geochronology of As-Hg-Sb accumulation. Core subsampling was performed by cutting 2-cm-thick slices of sediments. The subsamples were then analysed for several physical and chemical parameters. Sedimentation rate was assessed by measuring short-lived radionuclides (excess 210Pb and 137Cs). Pre-mining levels of As-Hg-Sb were observed at core depths below 50 cm. In the less extended salt marsh (eastern river bank), maximum As-Hg-Sb concentrations of 87.48, 3.66, and 5.75 µg·g-1, respectively, were found at the core top as a consequence of long-term mining activity in the area. The vertical distribution of As-Hg-Sb was influenced by the single-point contamination sources, whereas grain-size variability and diagenetic remobilisation did not seem affected. Geochronological measurements showed that the depositional fluxes of As-Hg-Sb were influenced by anthropogenic input after 1900, when mining activity in the area was most intense. Hg mining ceased in 1969; however, the corresponding core profiles did not show a drastic decreasing trend in element fluxes, implying that the river drainage basin retains some "memory" of contamination which affects riverine sediments. A preliminary gross estimation of total As-Hg-Sb "trapped" in the Nalón river salt marsh sediments amounted to approximately 18.7, 1.0, and 0.7 t, respectively. These morphological structures suffer erosive processes, thus representing a potential source of these elements associated with sediments; consequently, management conservation and monitoring of salt marshes should be taken into consideration from this environmental point of view.

Occurrence and speciation of arsenic and mercury in estuarine sediments affected by mining activities (Asturias, northern Spain).

Sediments contaminated by Hg and As from two historical mining areas have been deposited in the Nalón estuary (Asturias, northern Spain) since 1850. Total mercury (Hgtotal) concentrations in the sediments range from 0.20 µg g-1 to 1.33 µg g-1, most of it in the form of sulphides. Concentrations of methylmercury (303.20-865.40 pg g-1) are up to two orders of magnitude lower than the concentration of Hgtotal. Total As concentration (Astotal) is enriched compared to the background level for the area. The relative abundance of As(V) on As(III) in the sediments ranges from 97.6% to 100%, whereas inorganic Hg accounts for more than 99% of the total Hg. The occurrence of the most toxic species, inorganic As(III) and organic methylmercury, seem to be related to redox conditions together with the amounts of sulphur which act as natural barriers which inhibit the biological and chemical speciation processes. Despite the high amounts of Hg and As present in the sediments, their transference to the water column appear to be limited thus converting sediments in an effective sink of both elements. Special attention should be paid to potential variations of the environmental conditions which might increase the element mobility and exchange between sediments and the water column.

A risk assessment tool applied to the study of shale gas resources.

The implementation of a risk assessment tool with the capacity to evaluate the risks for health, safety and the environment (HSE) from extraction of non-conventional fossil fuel resources by the hydraulic fracturing (fracking) technique can be a useful tool to boost development and progress of the technology and winning public trust and acceptance of this. At the early project stages, the lack of data related the selection of non-conventional gas deposits makes it difficult the use of existing approaches to risk assessment of fluids injected into geologic formations. The qualitative risk assessment tool developed in this work is based on the approach that shale gas exploitation risk is dependent on both the geologic site and the technological aspects. It follows from the Oldenburg's 'Screening and Ranking Framework (SRF)' developed to evaluate potential geologic carbon dioxide (CO2) storage sites. These two global characteristics: (1) characteristics centered on the natural aspects of the site and (2) characteristics centered on the technological aspects of the Project, have been evaluated through user input of Property values, which define Attributes, which define the Characteristics. In order to carry out an individual evaluation of each of the characteristics and the elements of the model, the tool has been implemented in a spreadsheet. The proposed model has been applied to a site with potential for the exploitation of shale gas in Asturias (northwestern Spain) with tree different technological options to test the approach.

Heavy metal contamination in sediments of an artificial reservoir impacted by long-term mining activity in the Almadén mercury district (Spain).

Sediments from the Castilseras reservoir, located downstream on the Valdeazogues River in the Almadén mercury district, were collected to assess the potential contamination status related to metals(oids) associated with river sediment inputs from several decommissioned mines. Metals(oids) concentrations in the reservoir sediments were investigated using different physical and chemical techniques. The results were analyzed by principal component analysis (PCA) to explain the correlations between the sets of variables. The degree of contamination was evaluated using the enrichment factor (EF) and the geoaccumulation index (Igeo). PCA revealed that the silty fraction is the main metals(oids) carrier in the sediments. Among the potentially harmful elements, there is a group (Al, Cr, Cu, Fe, Mn, Ni, and Zn) that cannot be strictly correlated to the mining activity since their concentrations depend on the lithological and edaphological characteristics of the materials. In contrast, As, Co, Hg, Pb, and S showed significant enrichment and contamination, thus suggesting relevant contributions from the decommissioned mines through fluvial sediment inputs. As far as Hg and S are concerned, the high enrichment levels pose a question concerning the potential environmental risk of transfer of the organic forms of Hg (mainly methylmercury) from the bottom sediments to the aquatic food chain.

Arsenic partitioning among particle-size fractions of mine wastes and stream sediments from cinnabar mining districts.

Tailings from abandoned mercury mines represent an important pollution source by metals and metalloids. Mercury mining in Asturias (north-western Spain) has been carried out since Roman times until the 1970s. Specific and non-specific arsenic minerals are present in the paragenesis of the Hg ore deposit. As a result of intensive mining operations, waste materials contain high concentrations of As, which can be geochemically dispersed throughout surrounding areas. Arsenic accumulation, mobility and availability in soils and sediments are strongly affected by the association of As with solid phases and granular size composition. The objective of this study was to examine phase associations of As in the fine grain size subsamples of mine wastes (La Soterraña mine site) and stream sediments heavily affected by acid mine drainage (Los Rueldos mine site). An arsenic-selective sequential procedure, which categorizes As content into seven phase associations, was applied. In spite of a higher As accumulation in the finest particle-size subsamples, As fractionation did not seem to depend on grain size since similar distribution profiles were obtained for the studied granulometric fractions. The presence of As was relatively low in the most mobile forms in both sites. As was predominantly linked to short-range ordered Fe oxyhydroxides, coprecipitated with Fe and partially with Al oxyhydroxides and associated with structural material in mine waste samples. As incorporated into short-range ordered Fe oxyhydroxides was the predominant fraction at sediment samples, representing more than 80% of total As.

A compilation of field surveys on gaseous elemental mercury (GEM) from contrasting environmental settings in Europe, South America, South Africa and China: separating fads from facts.

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.

Arsenic contamination and speciation in surrounding waters of three old cinnabar mines.

The impact of arsenic pollution in waters from the surroundings of three abandoned Hg mines in Northern Spain, as well as reaching the Caudal River, was evaluated. For assessing the factors controlling arsenic release, an extensive study based on the physicochemical characterization and multivariate statistical analysis of waters upstream and downstream each mine site was performed. Waters downstream of the La Soterraña mine present the highest arsenic concentrations, up to 38.8 mg L(-1), coming mainly from the solubilisation of calcium, magnesium and strontium arsenates at a pH close to neutral. Although arsenic concentrations downstream of La Peña are markedly lower, these values remain too high, indicating that the encapsulation carried out in this spoil heap is insufficient. In addition, the high water flow in this point involves an extremely high input of arsenic to the surroundings (0.3 g s(-1)). Waters close to tailings from Los Rueldos suffer from acid mine drainage, provoking an important solubilisation of arsenic and heavy metals, a situation which is rapidly softened with distance. The study of arsenic speciation reveals the omnipresence of As(v) in waters from the three mines, whereas in La Peña low amounts of As(iii) were also detected. Different preservation methods for As speciation were compared, such as the addition of HCl, EDTA and the storage of samples without any additive, and no alteration of samples in any case up to nine months after the collection was observed. A study of seasonal variations of As and the main parameters affecting its concentration and speciation was completed throughout a year, showing no remarkable dependency with rainfall for any studied variable.

XANES speciation of mercury in three mining districts - Almadén, Asturias (Spain), Idria (Slovenia).

The mobility, bioavailability and toxicity of mercury in the environment strongly depend on the chemical species in which it is present in soil, sediments, water or air. In mining districts, differences in mobility and bioavailability of mercury mainly arise from the different type of mineralization and ore processing. In this work, synchrotron-based X-ray absorption near-edge spectroscopy (XANES) has been taken advantage of to study the speciation of mercury in geological samples from three of the largest European mercury mining districts: Almadén (Spain), Idria (Slovenia) and Asturias (Spain). XANES has been complemented with a single extraction protocol for the determination of Hg mobility. Ore, calcines, dump material, soil, sediment and suspended particles from the three sites have been considered in the study. In the three sites, rather insoluble sulfide compounds (cinnabar and metacinnabar) were found to predominate. Minor amounts of more soluble mercury compounds (chlorides and sulfates) were also identified in some samples. Single extraction procedures have put forward a strong dependence of the mobility with the concentration of chlorides and sulfates. Differences in efficiency of roasting furnaces from the three sites have been found.

Surface water monitoring in the mercury mining district of Asturias (Spain).

Systematic monitoring of surface waters in the area of abandoned mine sites constitutes an essential step in the characterisation of pollution from historic mine sites. The analytical data collected throughout a hydrologic period can be used for hydrological modelling and also to select appropriate preventive and/or corrective measures in order to avoid pollution of watercourses. Caudal River drains the main abandoned Hg mine sites (located in Mieres and Pola de Lena districts) in Central Asturias (NW Spain). This paper describes a systematic monitoring of physical and chemical parameters in eighteen selected sampling points within the Caudal River catchment. At each sampling station, water flow, pH, specific conductance, dissolved oxygen, salinity, temperature, redox potential and turbidity were controlled "in situ" and major and trace elements were analysed in the laboratory. In the Hg-mineralised areas, As is present in the form of As-rich pyrite, realgar and occasionally arsenopyrite. Mine drainage and leachates from spoil heaps exhibit in some cases acidic conditions and high As contents, and they are incorporated to Caudal River tributaries. Multivariate statistical analysis aids to the interpretation of the spatial and temporary variations found in the sampled areas, as part of a methodology applicable to different environmental and geological studies.

Atmospheric monitoring at abandoned mercury mine sites in Asturias (NW Spain).

Mercury concentrations are usually significant in historic Hg mining districts all over the world, so the atmospheric environment is potentially affected. In Asturias, northern Spain, past mining operations have left a legacy of ruins and Hg-rich wastes, soils and sediments in abandoned sites. Total Hg concentrations in the ambient air of these abandoned mine sites have been investigated to evaluate the impact of the Hg emissions. This paper presents the synthesis of current knowledge about atmospheric Hg contents in the area of the abandoned Hg mining and smelting works at 'La Peña-El Terronal' and La Soterraña, located in Mieres and Pola de Lena districts, respectively, both within the Caudal River basin. It was found that average atmospheric Hg concentrations are higher than the background level in the area (0.1 microg Nm(-3)), reaching up to 203.7 microg Nm(-3) at 0.2 m above the ground level, close to the old smelting chimney at El Terronal mine site. Data suggest that past Hg mining activities have big influences on the increased Hg concentrations around abandoned sites and that atmospheric transfer is a major pathway for Hg cycling in these environments.

Environmental impact of toxic metals and metalloids from the Muñón Cimero mercury-mining area (Asturias, Spain).

This paper presents the results of the sampling surveys carried out in order to evaluate the environmental problems associated to La Soterraña, an abandoned Hg mine in Asturias, north of Spain. In particular, this paper overviews the impact of mining and metallurgical activities on terrestrial and aquatic environments. The wastes generated during the mining activity (ore extraction and processing) and later accumulated on the ground, contain great amount of sulphides, becoming potentially acid-generating. Consequently, the mobility of heavy metals and other ecotoxic elements is enhanced. Wastes are generally located close to watercourses and on very steep hillsides, where they are exposed to oxidative weathering, posing a significant risk due to the release of ecotoxic elements to the environment. Background levels were determined at sites, which had not been directly affected by mercury mining. A multielemental geochemical study of mining wastes, soils, stream sediments, water and air samples collected in the area of influence of the old mining and metallurgical works was carried out. Total Hg and As concentrations in soils reach values up to 502 and 19,940 mg kg(-1), respectively, 500 and 2000 times higher than the local background levels. The effects of mining seem to be intense both in waters and stream sediments, as well as in the local atmosphere, whose Hg content is 10 times higher than the background level in the area. Therefore, the target carcinogenic risk was exceeded for As and Hg in La Soterraña site.

Physicochemical characterization and mercury speciation of particle-size soil fractions from an abandoned mining area in Mieres, Asturias (Spain).

Soils from old cinnabar mining areas usually exhibit high Hg contents, whose mobility depends on soil parameters and environmental conditions. This paper presents the study of the Hg speciation in soil samples from an abandoned Hg mine and metallurgical plant in Mieres (Asturias, Spain), in relation to their mineralogical and chemical composition and their particle-size distribution. A characterization of samples was made by X-Ray Diffraction Spectrometry, Scanning Electron Microscopy and Atomic Absorption and Emission Spectroscopy analyses. A sequential extraction method was applied to establish Hg mobility in the samples and their grain-size subsamples. The highest Hg mobility was found in well-developed soils, as a consequence of the adsorption processes by iron and manganese oxides, whereas in those more contaminated soils, a higher proportion of Hg was leached in the non-mobile fraction. A higher Hg mobility was found in the finest grain-size subsamples, probably due to the accumulation of clay minerals and oxides in these ranges.

Distribution and mobility of mercury in soils from an old mining area in Mieres, Asturias (Spain).

Mercury content in soils near abandoned mine wastes in the mercury mining area of Mieres (Asturias, Spain) is highly elevated as a result of the long period of mining and abundant Hg production. In this work, an evaluation of Hg concentration, distribution, and mobility in three soil samples from the immediate vicinity of a chimney used for vapour evacuation during pyrometallurgical treatment of the ore was carried out. For that purpose, total Hg contents were determined for the original samples and their grain-size subsamples. The study of mercury mobility in the original samples and in the different particle-size subsamples was made by the application of a sequential extraction method. Results showed that Hg concentration in soils decreases directly with the distance from the chimney and the dispersion of Hg is not influenced by the topographic height of the site tested. The sample collected in the base of the chimney exhibited appreciable amounts of mobile Hg. In general, a higher Hg concentration was found for the finest particle-size subsamples. Hg mobility was found to be higher for quite developed soils. The sample collected downstream from the chimney showed a significant Hg mobile content as a result of a more intensive weathering. An increase of Hg mobility at decreasing particle size was found in all three analysed samples.

Untreated abandoned mercury mining works in a scenic area of Asturias (Spain).

Mercury mining was a large and thriving industry during the last century in Asturias (NW Spain). At Brañalamosa, mining activity introduced significant quantities of wastes in spoil heaps located close to the mining operations. In these mining wastes, in addition to mercury, high concentrations of other potentially dangerous elements like As have been found. As a consequence, pollution and dereliction of the local environment occurred. This paper focuses on the environmental impact of these old mining operations and describes a preliminary assessment of the extent of contamination. This includes analytical data from systematic sampling of soils, stream sediments, wastes from spoil heaps, water and herbaceous plants in areas affected by mining activities. The potential risk that spoil materials imply for human health and the environment is documented on the basis of the application of EPA Risk Assessment methodology.

Investigation of trace element sources from an industrialized area (Avilés, northern Spain) using multivariate statistical methods.

In the industrialized urban area of Avilés (Spain), pooled soil samples from grassland sites were taken after careful sampling design and then investigated for their content of trace elements. A combination of statistic and geostatistic techniques proved to be a reliable tool in the interpretation of the analytical results. Geochemical groups and areas influenced mainly by anthropogenic activities were distinguished by means of classic multivariate methods (factor analysis and cluster analysis) and innovative geostatistical tools (Fourier spectral analysis). The constitution of the groups is supported by the linked results of methods sequentially distributed in order to extract as much information as possible from the original data.