Environmental Impact of Mining Activities in the Southern Sector of the Guadiana Basin (SW of the Iberian Peninsula)

Abstract

The southern sector of the Guadiana River basin (GRB) drains the central-western part of the Iberian Pyrite Belt, an area with many polymetallic sulfide deposits and residues of mining activities that under oxidizing conditions generate an acidic leachate with large quantities of sulfates, metals, and metalloids in solution. These acidic leachates seep into the fluvial system contaminating the surface water bodies and increasing the contamination risk for local populations and riparian habitats. The present study was carried out both in Portugal and Spain with the main aim of identifying the principal contamination sources that produce acid mine drainage (AMD) in the southern part of the GRB and to evaluate the seasonal variations of water quality affected by AMD. The physicochemical parameters determined in the field (temperature, electrical conductivity, pH, redox potential, and dissolved oxygen) are discussed and interpreted together with the hydrochemical analysis of surface water samples collected at 79 points of observation. The data show a strong seasonal variation of surface water quality with poorer water quality standards during the dry season. It is also possible to observe that there is a natural decrease in pollution levels with increasing distance from the pollution source (mining areas). Acidic leachates are gradually neutralized as they drain away from the mining areas depositing Fe-(Cu-Al) bearing secondary minerals. There is also an important contaminant load reduction in the estuary area as a result of the mixing process with seawater. This contributes to a loss of the metals in solution due to both dilution and precipitation, as a result of pH increase.

Toxicity assessment of contaminated soils from a mining area in Northeast Italy by using lipid peroxidation assay

“…Many characteristics of the studied soils vary; for example, the pH values oscillate from about 4 to nearly 8, due to the nature of the soil parent material; the highly acidic pH value found in site 4 soil is probably due to weathering oxidation of iron sulfides (pyrite and chalcopyrite) in the soil (Bini, in press;Delgado et al, 2009). Another parameter in the table is the CEC which has shown generally low values for all the soil samples (from 5.8 to 23.8 cmol c kg −1 ), except for the soils developed on dolomite (34.3 cmol c kg −1 , site 8).…”

The relevance of defining trace metal baselines in coastal waters at a regional scale: The case of the Portuguese coast (SW Europe)

“…1b), which is admittedly the largest sulphide mineralization in the world (Leistel et al, 1998). Weathering and mining activities have led to extremely high metal concentrations and acidity (pH < 3) in the rivers crossing this belt (Delgado et al, 2009). The most densely populated areas in the Portuguese coast are Porto, Aveiro, Lisbon and Faro (Fig.…”

A bacterial consortium isolated from an Icelandic fumarole displays exceptionally high levels of sulfate reduction and metals resistance

“…In Southern Portugal, AMD produced by abandoned mines located at the Iberian Pyrite Belt damage the adjacent riverine ecosystems through contamination of the aquatic biota and surrounding soils [2,3]. Although every mine is unique in terms of its AMD potential [1], the main AMD heavy metals in this region are usually Fe, Cu and Zn in concentrations of e.g.…”