Abstract
Over the course of history, the development of human societies implied the exploitation of mineral resources which generated huge amounts of mining wastes leading to substantial environmental contamination by various metal(loid)s. This is especially the case of coal mine tailings which, subjected to weathering reactions, produce acid mine drainage (AMD), a recurring ecological issue related to current and past mining activities. In this study, we aimed to determine the origin, the fate and the ecotoxicity of metal(loid)s leached from a historical coal tailing heap to the Beuveroux river (Franche-Comté, France) using a combination of mineralogical, chemical and biological approaches. In the constitutive materials of the tailings, we identified galena, tetrahedrite and bournonite as metal-rich minerals and their weathering has led to massive contamination of the water and suspended particles of the river bordering the heap. The ecotoxicity of the AMD has been assessed using Chironomus riparius larvae encaged in the field during a one-month biomonitoring campaign. The larvae showed lethal and sub-lethal (growth and emergence inhibition and delay) impairments at the AMD tributary and near downstream stations. Metal bioaccumulation and subcellular fractionation in the larvae tissues revealed a strong bioavailability of, notably, As, Pb and Tl explaining the observed biological responses. Thus, more than 70 years after the end of mining operations, the coal tailings remain a chronic source of contamination and environmental risks in AMD effluent receiving waters.
Highlights
The exploitation of mineral resources has contributed to the socio-economic development of human populations over the last millennia [1,2]
It can be noticed an increase of metal(loid) levels in the overlying water from the site entrance to the farthest downstream station
Pyrite oxidation generates acidity that could not be completely neutralized by the presence of carbonate-bearing minerals in the shale of the coal basin [20] leading to a pH of the acid mine drainage (AMD) effluent around 4
Summary
The exploitation of mineral resources has contributed to the socio-economic development of human populations over the last millennia [1,2]. The mineral related activities constitute the most ancient and significant source of waste production These remains, often rich in metallic elements, may represent an environmental risk during their production and after the end of the operations. Once abandoned they can be subjected to weathering phenomenon and subsequently release metal(loid)s in various environmental compartments [3]. This is especially the case of sulfidic residues which, exposed to air and water, generate acidic conditions favoring the leaching of metals that originate from native rocks of the tailings [4]. This process is well-known as acid mine drainage (AMD)
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