Mari Luz García-Lorenzo

Geochemical characterisation of surface waters, topsoils and efflorescences in a historic metal-mining area in Spain

PurposeMining activities generate large amounts of wastes that may contain potentially toxic elements (PTE), which, if released into the environment, may cause air, water and soil pollution long after mining operations have ceased. This paper describes the environmental relevance of efflorescences, topsoils and surface waters from the abandoned mine of Sierra Minera of Cartagena-La Unión, SE Spain. The exposure of the population to arsenic and the associated risk were also assessed.Materials and methodsA total of 10 topsoils and surface waters and 11 efflorescences affected at varying degrees by mining activities were studied. The total potentially toxic element content (As, Cd, Cu, Fe, Pb and Zn) was determined in all samples. In addition, the mineralogical composition of solid samples was determined by X-ray diffraction and some efflorescences were also analysed using a scanning electron microscopy-energy dispersive X-ray spectrometer. Finally, an arsenic-intake risk assessment was carried out, both as regards carcinogenic and non-carcinogenic effects and considering the total and the bioaccesible As content.Results and discussionThe study area is heavily polluted as a result of historical mining and processing activities, during which time great amounts of wastes were produced, characterised by a high PTE content, acidic pH and minerals resulting from supergene alteration. The supergene mineralogical assemblages include soluble metal salts, mainly sulphates, iron hydroxysulphates and iron oxyhydroxides, all of which form ochreous precipitates. Topsoil samples showed risk values and hazard quotients higher than the reference levels, particularly for children. In the efflorescences, these values were lower but still unacceptable.ConclusionsThe efflorescences are of significance for monitoring purposes because they are involved in cycles of retention release of hydrogen ions, sulphate and potentially toxic elements. In addition, in a semi-arid climate, such as the study area, these minerals contribute to our understanding of the response of the system to episodic rainfall events. In general, it was observed that the arsenic in collected samples represent a potential risk for human health through ingestion.

Impact of acid mine drainages on surficial waters of an abandoned mining site

Weathering of sulphide minerals produces a great variety of efflorescences of soluble sulphate salts. These minerals play an important role for environmental pollution, since they can be either a sink or a source for acidity and trace elements. This paper aims to characterise surface waters affected by mining activities in the Sierra Minera of Cartagena-La Union (SE, Spain). Water samples were analysed for trace metals (Zn, Cd, Pb, Cu, As and Fe), major ions (Na+, K+, Ca2+ and Mg2+) and anions (F−, Cl−, NO3−, CO32−, SO42−) concentrations and were submitted to an “evaporation-precipitation” experiment that consisted in identifying the salts resulting from the evaporation of the water aliquots sampled onsite. Mineralogy of the salts was studied using X-ray diffraction and compared with the results of calculations using VISUAL MINTEQ. The study area is heavily polluted as a result of historical mining and processing activities that has produced large amount of wastes characterised by a high trace elements content, acidic pH and containing minerals resulting from the supergene alteration of the raw materials. The mineralogical study of the efflorescences obtained from waters shows that magnesium, zinc, iron and aluminium sulphates predominate in the acid mine drainage precipitates. Minerals of the hexahydrite group have been quantified together with minerals of the rozenite group, alunogen and other phases such as coquimbite and copiapite. Calcium sulphates correspond exclusively to gypsum. In a semiarid climate, such as that of the study area, these minerals contribute to understand the response of the system to episodic rainfall events. MINTEQ model could be used for the analysis of waters affected by mining activities but simulation of evaporation gives more realistic results considering that MINTEQ does not consider soluble hydrated salts.

Bone mineral change during experimental calcination: an X-ray diffraction study.

The effects of calcination (400–1200°C) on pig bones have been studied using powder X‐ray diffraction (XRD) and secondary modifications, such as color change and weight loss. The characterisation by powder XRD confirmed the presence of the crystalline phase of hydroxyapatite, and comparison of the results obtained at different temperatures suggested that at 650°C, all the organic components and carbonate substitutions were completely removed. Accordingly, these samples were white. In addition, the crystallinity degree and the crystallite size progressively increased with the calcination temperature until 650°C, remaining stable until 1200°C. Below 650°C, bone samples presented organic compounds, resulting in background noise in the diffractogram and gray or black color. In addition, impurities in the lattice correspond to low crystallite sizes.

Heavy metal immobilisation by limestone filler in soils contaminated by mining activities: Effects on metal leaching and ecotoxicity

The leachability and ecotoxicity of potentially toxic elements (PTE) eluting from technosols formed of soils affected by mining activities and limestone filler were evaluated. A total of four contaminated soils affected by opencast mining were selected and mixed with limestone filler at three percentages: 10, 20 and 30 %, providing 12 stabilised samples. Total and soluble PTE content (As, Cd, Cu, Fe, Pb and Zn) was determined in all the samples and the Microtox® bioassay was applied to determine the ecotoxicological effect. The stabilised material had a neutral pH and low soluble PTE concentration. Moreover, the ecotoxicological assay indicated the presence of low toxicity levels in the stabilised samples. The applied bioassay can be considered a good tool for the screening of PTE contamination in areas affected by mining activities, while providing information about possible attenuation processes.

Assessment of potentially toxic element contamination in soils from Portman Bay (SE, Spain)

PurposeThe present study deals with the geochemical fractions of Pb, Cd, Zn, Cu and As present on profiles using chemical simple extraction process. This work was conducted on Portman Bay, located in the SE Spain and strongly affected by mining activities.Materials and methodsFour simple extractions were applied to selected samples in order to evaluate the potential mobility of metals. X-ray diffraction (XRD) was applied to the characterisation of samples and the residues remaining after each extraction, providing additional information about the sediment phases carrying the elements studied.Results and discussionThe results obtained after the extractions suggested that the highest potentially toxic element (PTE) content was obtained in the oxidising medium. The mineralogical composition is an important factor that should be taken into account in the evaluation of PTE mobility, firstly because the mineral phases react differently in the proposed situations depending on their chemical nature, and secondly, because the presence of a particular phase depends on the degree of weathering.ConclusionsThe evaluation of PTE mobility and mineralogical composition under different environmental conditions may be very important in the execution of restoration projects which could involve dredging and mobilisation of materials.

Pb–Zn–Cd–As Pollution in Soils Affected by Mining Activities in Central and Southern Spain: A Scattered Legacy Posing Potential Environmental and Health Concerns

In this chapter, published geochemical data for soils from several Pb–Zn mine sites and districts from Spain are reviewed. Although most of the mines have closed down, a legacy of highly polluted soils still remains throughout the sites constituting a potential hazard for the environment and human health. The fate of the studied metals and metalloids in these soils is mainly controlled by factors such as mining methods, concentration and metallurgical operations, mineralogy of the ore, gangue and host rock, fracturing of the host rocks, physiography, climate, and soil types (pedogenic evolution). It can be concluded that the most polluted soils (identified on the basis of an enrichment factor) are those of the Sierra Minera (La Union District – SE Spain), at more than 488 (Pb), 163 (Zn), 99 (Cd), and 98 (As) times the background values from non-contaminated soils. Pb is usually related to As, which in turn is bound to Fe oxides and oxyhydroxides. Metal bearing jarosite and other soluble phases also play a relevant role in the studied soil–water systems, because these minerals are dissolved during intense rainy events, thus resulting in high rates of metal leaching and mobilization by runoff.

Spatial distribution and sources of trace elements in sediments affected by old mining activities

The distribution of trace elements throughout mining areas is an important issue because abandoned tailings could be a major source of environmental pollution. In order to analyze the spatial variation of trace elements in a zone where mining activities took place and to identify pollution sources in the study area, a three-step study was carried out at a regional, at a local, and a detailed scale. In addition, a conceptual model of trace elements dispersion was established and confirmed by a geographic information system. The results obtained allowed to establish points affected by primary, secondary, and tertiary contamination, according to their proximity to contamination sources and as a function of attenuation processes which could take place in the studied area.

Assessment of the Acoustic Impact of Wind Farm Projects: Methodology and Case

Wind energy is a clean renewable and its benefits are considered greater than the disadvantages. However, even though wind farms represent environmentally friendly projects, they frequently generate public resistance. Wind turbines are socially controversial because of their visual and acoustic impacts. The aim of this work was to design a methodology for the preliminary evaluation of potential acoustic impact of wind farms. Three steps have been proposed: identification, characterization and assessment of the acoustic impact during the construction, operation and decommissioning phase. Obtained results in the studied area suggested that at a maximum power, at 500 meters of wind turbines, noise level is lower than the reference level established in the legislation. In summary, proposed methodology could help to determine and to evaluate the best location for new wind farm projects. Proposed methodology could help to determine and to evaluate the best location for new wind farm projects. Moreover, this method could be used as a consulting tool for public organizations and private institutions, being quick, concise and clear. Obtained results for the studied wind farm project suggested that almost all the area showed noise levels lower than established background noise level.

Potential bioavailability assessment and distribution of heavy metal(oids) in cores from Portman Bay (SE, Spain)

A total of 120 sediments from 12 cores of Portman Bay (SE Spain) were studied to assess the degree of contamination and ecological risk related to potentially toxic elements (PTEs) by combining a geochemical and mineralogical characterization with the assessment of the bioavailable forms of trace metals (As, Cd, Cu, Fe, Pb, Zn). With this purpose, sediment contamination was assessed by total and water-soluble content, and potential bioavailability by the simultaneously extracted metals and acid-volatile sulphides (SEM-AVS) approach, and by an oral bioaccessibility extraction procedure. The sediments are essentially sandy (>80%). The most important minerals are: iron phases such as siderite, iron oxides and hydroxides and pyrite; clay minerals such as clinochlore, greenalite and biotite; and quartz. Occasionally, jarosite and carbonates (calcite and dolomite) appear. The total PTEs content is high whereas the sediments generally have a very low soluble PTE content. The SEM/AVS ratio is less than unity in most samples, indicating that there is enough sulphur so that if there was a release of metals, they could precipitate as sulphides. After the bioaccessibility extraction, the results showed that zinc and cadmium are more bioaccessible in the intestinal environment (alkaline) while the rest of the elements have greater availability in the stomach (acid). Supplementary material: values of pH (1:1 extract) and concentration of different metals and arsenic in the sediments studied is available at https://doi.org/10.6084/m9.figshare.c.4272176

Proposals for the Remediation of Soils Affected by Mining Activities in Southeast Spain

Abstract The zones affected by long-term mining activities are currently of special interest since they represent a contamination focus influencing large areas. These particular sites are usually abbreviated as CAMAs (critical abandoned mining areas). Sierra Minera of Cartagena-La Union is a CAMA with an interesting and valuable ecosystem that needs adequate management tools. Suitable management should be based on the results of a risk assessment procedure, based on proximity to populations or the use that a specific space may have. The risk assessment needs to consider human health and/or ecosystems. The most serious concern in this respect is the behavior and fate of potentially toxic elements such as lead, cadmium, zinc and arsenic, which were present in the raw materials and may be bioavailable. Remediation measures would be based on the natural attenuation of impacts that have occurred in this area and would include neutralization of the acid mine drainage, increase of the natural vegetation favoring the growth of tolerant species (even with low transference factors), and gully regulation in order to avoid spills on crops or at sea.