The Evolution of Pollutant Concentrations in a River Severely Affected by Acid Mine Drainage: Río Tinto (SW Spain)

Abstract

The Río Tinto, located in the Iberian Pyrite Belt (SW Spain), constitutes an extreme case of pollution by acid mine drainage. Mining in the area dates back to the Copper Age, although large-scale mining of massive sulfide deposits did not start until the second half of the 19th century. Due to acidic mining discharges, the Río Tinto usually maintains a pH close to 2.5 and high concentrations of pollutants along its course. From a detailed sampling during the hydrological year 2017/18, it was observed that most pollutants followed a similar seasonal pattern, with maximum concentrations during autumn due to the washout of secondary soluble sulfate salts and minimum values during large flood events. Nevertheless, As and Pb showed different behavior, with delayed concentration peaks. The dissolved pollutant load throughout the monitored year reached 5000 tons of Fe, 2600 tons of Al, 680 tons of Zn, and so on. While most elements were transported almost exclusively in the dissolved phase, Fe, Pb, Cr, and, above all, As showed high values associated with particulate matter. River water quality data from 1969 to 2019 showed a sharp worsening in 2000, immediately after the mine closure. From 2001 on, an improvement was observed.

Metal(loid) release from sulfide-rich wastes to the environment: The case of the Iberian Pyrite Belt (SW Spain)

“…Owing to the orphan nature of most mine sites in the IPB, environmental liabilities are often assumed by the public administration, and thus, the scarcely reported cases of restoration measures were put in practice by the regional government [35,36]. Notwithstanding, the reopening of mines in the IPB may suppose a breaking point in this environmental quandary since permits require that mining companies must take over the environmental liabilities from past mining, and thus, a remarkable improvement of environmental conditions is expected in the short term [37,38].…”

Use of propionic acid additions to enhance zinc removal from mine drainage in short residence time, flow-through sulfate-reducing bioreactors

“…Low pH, high metal concentration mine discharges are among the most ecologically damaging effluent types world-wide (Olías et al, 2020). In the UK zinc is particularly prevalent in drainage from abandoned metal mines with over 50% of the total zinc flux to freshwaters of England and Wales attributed to such pollution (Mayes et al, 2013).…”

Assessment of the Environmental Impact of Acid Mine Drainage on Surface Water, Stream Sediments, and Macrophytes Using a Battery of Chemical and Ecotoxicological Indicators

“…Indeed, names such as Roxo, Ribeira da Água Forte (strong water stream, in Portuguese), and Ribeira da Água Azeda (sour water stream, in Portuguese) provides a safe indication of the characteristics of the surface water of the hydrological system in the Aljustrel area. An identical example is the Rio Tinto (red or dark river), in the Spanish sector of IPB, whose water is also heavily polluted by the AMD from the abandoned mines in the region, i.e., the Peña del Hierro and Rio Tínto mines, located in the river's headwaters [15,21].…”

“…The results reported in this study, and in other studies that have assessed the environmental impact in the Aljustrel mining area [2-4,9,22,23] can be used to evaluate the benefits of the remediation measures at the site, documenting the "ground zero" Several studies have documented these impacts in rivers and streams, in Aljustrel [3,9,[22][23][24], and also in other mines from the IPB, both in Portugal, for example, the Lousal mine, affecting the Corona stream [18,25,26], São Domingos, affecting the São Domingos stream, a tributary to the Chança river [10,27] and, in Spain, mainly in Tinto and Odiel river basins, affected by different mines, for example, Rio Tinto, Tharsis, and Sotiel-Coronado [15,17,21,[28][29][30][31][32][33], in the Oraque and Meca rivers (Odiel tributaries), affected by the Tharsis mine [33], also affecting the Chanza and Guadiamar rivers [32]. In fact, in specific hydrogeochemical conditions, the environments affected by AMD can be characterized by extreme conditions, for example, negative pH values [33], similar to those found in the Cobica River basin, affected by AMD-polluted waters coming from the Lagunazo mine and the Herrerias mine, where, in addition to the high concentrations of toxic elements, the mean pH value was negative (pH = −1.56) [34].…”