Almudena Ordóñez

A comparative study of heavy metal concentration and distribution in deposited street dusts in a large and a small urban area: Birmingham and Coventry, West Midlands, UK

Results are presented from a study of the distribution of heavy metals in street dusts of two cities in Midland England. The first (Birmingham) is a large urban area (population of 2.3 million), the second, Coventry, a small one (population of 0.3 million). Several trends were identified from Birmingham: higher concentrations were located near industrial areas in the northwest of the city and within the ring road. However, lower concentrations were found to the southwest in areas of mainly residential properties and parks. High values were also identified in association with junctions controlled by traffic lights where vehicles were likely to stop regularly. This last trend was further investigated in Coventry, where it was found that concentrations of heavy metals at junctions controlled by traffic signals and by pedestrian-controlled pelican lights (Mounted Pelican Controller, MPCs) were lower than those found in Birmingham, apart from Ni.

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.

A review of the distribution of particulate trace elements in urban terrestrial environments and its application to considerations of risk

We review the evolution, state of the art and future lines of research on the sources, transport pathways, and sinks of particulate trace elements in urban terrestrial environments to include the atmosphere, soils, and street and indoor dusts. Such studies reveal reductions in the emissions of some elements of historical concern such as Pb, with interest consequently focusing on other toxic trace elements such as As, Cd, Hg, Zn, and Cu. While establishment of levels of these elements is important in assessing the potential impacts of human society on the urban environment, it is also necessary to apply this knowledge in conjunction with information on the toxicity of those trace elements and the degree of exposure of human receptors to an assessment of whether such contamination represents a real risk to the city’s inhabitants and therefore how this risk can be addressed.

Geochemical characterisation of mercury mining spoil heaps in the area of Mieres (Asturias, northern Spain)

Abstract Asturias has important and abundant mercury deposits, and the legacy of the historical mining activities remains in the form of old and abandoned industrial installations. In areas where years of mercury mining has occurred, large amounts of wastes with high contents of Hg and As were disposed on the surface, without any preventive measures to avoid ore leaching and the dispersion of toxic elements into the environment. In proximity to Mieres village, three spoil heaps (El Terronal, El Rucio, and Los Rueldos) were selected to undertake a multielemental geochemical study of soils, water and plants. In soils, systematic sampling was carried out at the site of the old mining and metallurgical works in El Terronal. Spoil heaps were also systematically sampled at the sites of El Terronal, El Rucio and Los Rueldos. In the area of El Terronal, different types of plants have been sampled, including grass, fruit trees, edible crops and thickets. The soluble fraction resulting from a strong acid attack of the sample was analysed by FAA and ICP. Superficial water was sampled monthly, upstream and downstream of mining works; data obtained from filtered samples include pH, Eh, and arsenic and mercury concentrations. Soil samples from the mined areas show mercury concentrations between 1.7 and 472.1 mg/kg, and arsenic concentrations between 6 and 7287 mg/kg. Arsenic content in samples of spoil heaps is in the range 4746–62,196 mg/kg (Los Rueldos), and 192–2057 mg/kg (El Rucio); mercury content is in the range 14–2224 mg/kg (Los Rueldos), and 21–1984 mg/kg (El Rucio). Arsenic content of superficial water upstream and downstream of the mining works is lower than 0.005 mg/l (analytical detection limit), and 0.9–5.6 mg/l, respectively; mercury concentrations upstream and downstream of mining works are always lower than 0.001 mg/l (analytical detection limit). Leachates collected at the bottom of the Los Rueldos spoil heap show acidic pH (between 2.43 and 2.50), Eh around 550 mV, arsenic concentrations between 5.3 and 8.3 mg/l, and mercury concentrations always lower than 0.001 mg/l (analytical detection limit). Maximum values of As and Hg content in grass in the mined area are 53 mg/kg and 4.84 mg/kg, respectively.

Influence of industry on the geochemical urban environment of Mieres (Spain) and associated health risk.

This study is concerned with the elemental composition of soils and street dust collected in an historical industrial city of approximately 27 000 inhabitants, where old Hg mining and metallurgical activities strongly affected the load of heavy metals in the urban environment. For the purpose of the study, representative samples of soils and street dust were collected at different locations in the whole urban area (3 km2). Elevated mean concentrations of As in soils and street dust (69 and 135 μg g−1, respectively), and Hg (3.07 and 4.24 μg g−1, respectively), compared to background levels and to those found in other cities, reflect the anomalous geochemical nature of these materials and the strong influence exerted by the old mining sites.

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.

Asturian mercury mining district (Spain) and the environment: a review

Mercury is of particular concern amongst global environmental pollutants, with abundant contaminated sites worldwide, many of which are associated with mining activities. Asturias (Northwest of Spain) can be considered an Hg metallogenic province with abundant epithermal-type deposits, whose paragenetic sequences include also As-rich minerals. These mines were abandoned long before the introduction of any environmental regulations to control metal release from these sources. Consequently, the environment is globally affected, as high metal concentrations have been found in soils, waters, sediments, plants, and air. In this paper, a characterization of the environmental affection caused by Hg mining in nine Asturian mine sites is presented, with particular emphasis in Hg and As contents. Hg concentrations found in the studied milieu are similar and even higher than those reported in previous studies for other mercury mining districts (mainly Almadén and Idrija). Furthermore, the potential adverse health effects of exposure to these elements in the considered sites in this district have been assessed.

Arsenic mobilization from waste piles of the El Terronal mine,Asturias, Spain

Arsenic is associated with Hg in the mercury deposits of the Asturias region of northern Spain. Until 1974, the mines of La Peña and El Terronal exploited an ore deposit located in the valley of the San Tirso River (Mieres district). At this site, a great volume of waste material from mining and metallurgical works have been stock-piled for years, constituting a spoil heap of about 20 000 m2 in area. Total As concentrations in representative samples of waste materials on the surface of the spoil heap reach a maximum value of 72 153 mg kg−1 and an average value of 15 967 mg kg−1; analysis of deeper samples (trenches on the spoil heap) exceed 99 999 mg kg−1. The total flow of polluted water from its circulation through the spoil heap is estimated at 3465 m3 a−1. Weathering processes facilitate the dissolution and leaching of As and heavy metals in the ore and waste material. Arsenic contents in surface waters (San Tirso River) immediately downstream of the spoil heap reach 7.9 mg l−1. The impact on the area, reflected by elevated concentrations of As in adjacent soils, biota and surface/underground waters, is discussed.

Hydraulic and Thermal Modelling of an Underground Mining Reservoir

Flooded mines are a groundwater reservoir that can be used geothermally. Modelling such a reservoir can be complicated because it is necessary to simultaneously solve the equations of flow and heat transport within the mine voids and the surrounding medium, whose hydraulic parameters may have been affected by mining. We present a numerical model developed for the reservoir formed by the Barredo and Figaredo shafts in the Central Coal Basin of Asturias (Spain), using FEFLOW software. Both 2- and 3-D versions of the model were used to simulate the flooding of the mine. They were calibrated by comparing the results with actual water levels measured during flooding. The hydrogeological and thermal characteristics of the reservoir were adjusted to predict the long-term temperature of the water under different scenarios of water extraction and injection.ZusammenfassungGeflutete Bergwerke bilden ein Grundwasserreservoir, welches geothermisch genutzt werden kann. Die Modellierung solcher Speicher ist jedoch kompliziert, da bei der Simulation Fließ- und Wärmetransportgleichungen sowohl in den Grubenhohlräumen als auch in den umgebenden Gesteinen gemeinsam gelöst werden müssen, wobei die hydraulischen Parameter zudem durch den Bergbau beeinflusst sind. Es wird ein numerisches Modell präsentiert, welches für das Grundwasserreservoir der Bergbaufelder von Barredo und Figaredo im zentralen Kohlebecken von Astriuas (Spanien) entwickelt worden ist. Sowohl 2-D als auch 3-D Versionen der Software FEFLOW wurden verwendet, um die Flutung des Untertagebergbaus nachzubilden. Die Modelle wurden kalibriert, indem die Modellergebnisse mit aktuellen Wasserständen während der Flutung verglichen wurden. Die hydrogeologischen und geothermischen Parameter des Reservoirs wurden angepasst, um langzeitliche Temperaturentwicklungen im Wasser bei verschiedenen Entnahme- und Injektionsszenarien vorherzusagen.ResumenLas minas inundadas constituyen un embalse de agua subterránea, del que se puede hacer un aprovechamiento geotérmico. Modelizar este tipo de embalses puede resultar complejo, ya que es necesario resolver simultáneamente las ecuaciones de flujo y transporte de calor en los huecos mineros y el medio circundante, cuyos parámetros hidrogeológicos pueden haber resultado afectados por la actividad minera. Se presenta un modelo numérico desarrollado para el embalse constituido por los pozos mineros Barredo y Figaredo en la Cuenca Carbonífera Central de Asturias (España), por medio del software FEFLOW. Se realizaron versiones del modelo en 2 y 3 dimensiones para simular la inundación de la mina, que fueron calibradas comparando los resultados con los valores reales de nivel de agua medidos durante dicha inundación. Las características hidrogeológicas y térmicas del embalse fueron ajustadas para predecir la temperatura a largo plazo del agua bajo diferentes escenarios de extracción de agua y reinyección.抽象闭坑(或废弃)淹没矿坑可用作提供地热的地下水库。由于需要同时求解矿坑及周围介质的水力学和热力学方程以及方程水文地质参数受矿坑严重影响,地下水库的水力与热力学数值模拟比较复杂。利用 FEFLOW建立了西班牙阿斯图里亚斯地区(Asturias)中央聚煤盆地(Central Coal Basin)Barredo井与Figaredo竖的地下水库模型。同时利用二维和三维模型模拟了矿坑淹没过程,用矿坑淹没期间实际观测水位进行了模型识别。地下水库模型经水文地质学及热力学特征校正后用以预测不同抽水、注水情形下的水温长期预测。

Hydrochemical characterization of a mine water geothermal energy resource in NW Spain

Abandoned and flooded mine networks provide underground reservoirs of mine water that can be used as a renewable geothermal energy source. A complete hydrochemical characterization of mine water is required to optimally design the geothermal installation, understand the hydraulic behavior of the water in the reservoir and prevent undesired effects such as pipe clogging via mineral precipitation. Water pumped from the Barredo-Figaredo mining reservoir (Asturias, NW Spain), which is currently exploited for geothermal use, has been studied and compared to water from a separate, nearby mountain mine and a river that receives mine water discharge and partially infiltrates into the mine workings. Although the hydrochemistry was altered during the flooding process, the deep mine waters are currently near neutral, net alkaline, high metal waters of Na-HCO3 type. Isotopic values suggest that mine waters are closely related to modern meteoric water, and likely correspond to rapid infiltration. Suspended and dissolved solids, and particularly iron content, of mine water results in some scaling and partial clogging of heat exchangers, but water temperature is stable (22°C) and increases with depth, so, considering the available flow (>100Ls-1), the Barredo-Figaredo mining reservoir represents a sustainable, long-term resource for geothermal use.