Work

A first approach to the characterization of water and sediments during the restoration of coal waste dumps in El Bierzo (NW Iberia)

Year: 2025

Type: article

Abstract: Coal mining has been related to the problems of acid mine drainage (AMD) or acid rock drainage (ARD), causing high acidity and contamination by metals. Coal mining in El Bierzo coal basin, NW Iberian Peninsula, has resulted in several abandoned tailings from past mining that still affect water chemistry and sediment composition. Recent restoration actions, including the expansion of roads, have introduced fresh waste materials and accelerated the oxidative weathering and sediment transport into La Silva river. Water analyses continue to show low pH (~4.5) and high sulfate concentrations supporting sulfide oxidation. The VNIR-SWIR diffuse reflectance spectroscopy initially identified iron oxides such as goethite in the sediments, and later illite, a product of erosion and deposition of waste materials. This indicates that the runoff generated after the rainfall episodes has transported sediments of different mineral composition by mobilizing material from the waste dumps. The study highlights the importance of continuous monitoring to assess the evolving geochemical conditions and potential secondary alterations in the river system. Reflectance spectroscopy has proved to be a useful technique for rapid mineral identification, distinguishing oxidation effects from erosion impacts, making it a valuable tool for environmental assessments.

Source: Geogaceta

DOI: 10.55407/geogaceta113534