Spatial evolution of an AMD stream in the Iberian Pyrite Belt: process characterization and control factors on the hydrochemistry

This paper presents hydrochemical data of an AMD stream in the Iberian Pyrite Belt, obtained from its source, in the Poderosa Mine Portal, till its confluence at the Odiel River. The main objective is to establish potential interdependent relations between sulfate and metals’ loads and the following physical-chemical variables: pH, electric conductivity (EC), redox potential (EH), and dissolved oxygen (O2). All the parameters show a global increasing tendency since the tunnel’s exit to the confluence at Odiel River. The TDS and EC are two relevant exceptions. They behave similarly, showing a decreasing trend and a strong inflection that describes a minimum immediately after the discharging point. The spatial analysis combined with statistical tools put in evidence the typical AMD processes and the respective physical-chemical implications. Inputs with distinctive hydrochemical signatures impose relevant modifications in the Poderosa creek waters. This indicates low hydrochemical inertia and high vulnerability to external stimulus.Financial support for this research was provided by DGCICYT National Plan, project CGL2010-21268-C02-01 and the Andalusian Autonomous Government Excellence Projects, Project RNM-6570

Hydrochemical characterization of an acid mine drainage-affected water reservoir : the Sancho Dam (Huelva, SW Spain)

The present study has the following objectives: to discover the relation between variables and the hydrochemical variations related to acid mine drainage in a water reservoir, and to describe horizontal stratification relating to vertical salinity and variations in metals. The information obtained may be used for establishing risk evaluation criteria and to design future remediation strategies, which could be useful for new dams. The hydrochemical characterization was based on a sampling campaign performed in October, 2011. A total of 28 samples, at one-meter-deep intervals, were obtained. The hydrogeochemical study of the polluted reservoir showed that the dilution effect is not sufficient to neutralize Acid Mine Drainage contributions from mining activity. Sampling carried out from the surface water to the deepest points reveals the reservoir stratification, which allows it to be included in the group of monomictic and holomitic lakes.This study is a contribution to the projects (CICYT-REN2002-1,897/HID, CICYT-TIN20046,689-C03-03 and DGCICYT-CGL2010-21,268-C02-01) financed by the Spanish Ministry of Education and Science; and the Andalusian Autonomous Government Excellence Projects (project P06-RNM-2,167)

Characterization of water reservoirs affected by acid mine drainage: geochemical, mineralogical, and biological (diatoms) properties of the water

This work presents a combination of geochemical, mineralogical, and biological data obtained in water reservoirs located in one of the most paradigmatic mining regions, suffering from acid mine drainage (AMD) problems: the Iberian Pyrite Belt (IPB). Four water reservoirs located in the Spanish sector of the IBP, storing water for different purposes, were selected to achieve an environmental classification based on the effects of AMD: two mining dams (Gossan and Águas Ácidas), a reservoir for industrial use (Sancho), and one with water used for human supply (Andévalo). The results indicated that the four reservoirs are subject to the effect of metallic loads from polluted rivers, although with different levels: Águas Ácidas > Gossan > Sancho ≥ Andévalo. In accordance, epipsammic diatom communities have differences in the respective composition and dominant taxa. The dominant diatoms in each reservoir indicated acid water: Pinnularia acidophila and Pinnularia aljustrelica were found in the most acidic dams (Gossan and Águas Ácidas, with pH <3), Pinnularia subcapitata in Sancho (pH 2.48-5.82), and Eunotia exigua in Andévalo (pH 2.34-6.15).The authors thank to António Azevedo for his help in XRD analysis and to Elisabete Vivas for her assistance with the preparation of clay fraction. Financial support for this research was provided by DGCICYT National Plan, Project CGL2010-21268-C02-01 and Project RNM-6570.The authors are grateful to two anonymous reviewers for their valuable comments and suggestions.info:eu-repo/semantics/publishedVersio

Definition of redox and pH influence in the AMD mine system using a fuzzy qualitative tool (Iberian Pyrite Belt, SW Spain)

Poderosa Mine is an abandoned pyrite mine, located in the Iberian Pyrite Belt which pours its acid mine drainage (AMD) waters into the Odiel river (South-West Spain). This work focuses on establishing possible reasons for interdependence between the potential redox and pH, with the load of metals and sulfates, as well as a set of variables that define the physical chemistry of the water-conductivity, temperature, TDS, and dissolved oxygen-transported by a channel from Poderosa mine affected by acid mine drainage, through the use of techniques of artificial intelligence: fuzzy logic and data mining. The sampling campaign was carried out in May of 2012. There were a total of 16 sites, the first inside the tunnel and the last at the mouth of the river Odiel, with a distance of approximately 10 m between each pair of measuring stations. While the tools of classical statistics, which are widely used in this context, prove useful for defining proximity ratios between variables based on Pearson's correlations, in addition to making it easier to handle large volumes of data and producing easier-to-understand graphs, the use of fuzzy logic tools and data mining results in better definition of the variations produced by external stimuli on the set of variables. This tool is adaptable and can be extrapolated to any system polluted by acid mine drainage using simple, intuitive reasoning.The study is a contribution to the DGCICYT-CGL2010-21268-C02-01 project, which is financed by the Spanish Ministry of Education and Science, and the Andalusian Autonomous Government Excellence Project, code P06-RNM-02167.info:eu-repo/semantics/publishedVersio

Impact of AMD processes on the water dams of the Iberian Pyrite Belt : overall hydrochemical characterization (Huelva, SW Spain)

In the Iberian Pyrite Belt (IPB), the process of acid mine drainage (AMD) is anthropogenic in origin. The impact of AMD pollution processes is characterised in 23 dams in the IPB. Based on the pH values, three groups are established: group 1 (pH5). Group 1 has the lowest pH values, with all of them lower than 3 and a minimum value of 1.9. The pH values are higher in the other groups, with lower values in group 2 (between 2.34 and 6.15) and higher in group 3 (between 4.36 and 7.58). Conductivity is higher in group 1 (varying between 1,005 and 12,280 μScm−1), while it takes intermediate values in group 2 (between 139 and 2,652 μScm−1), and group 3 is the lowest (between 80 and 750 μScm−1). Among the ions analysed, the concentration of sulphates stands out due to its magnitude, which is always greater than that of the other ions in the three groups. It is in group 1 that it reaches the highest values, with 6,200 mg/L, while it is lower in the others. Applying variable cluster analysis shows that in group 1, pH exercises control over the dissolution of most of the metals. It is also sulphates that control the value for conductivity. In group 2, precipitation is the main variable that controls the dissolution of ions, with the influence of pH being lower. In group 3, it is observed that in pH control metals, conductivity is controlled by sulphates.Spanish Ministry of Education and Science and the Andalusian Autonomous Government Excellence Project, code P06-RNM-02167