Natural acid rock drainage in alpine catchments : a side effect of climate warming
Zarroca Bonet, Mario (Universitat Autònoma de Barcelona. Departament de Geologia)
Roqué Pau, Carles (Universitat de Girona. Àrea de Geodinàmica Externa i Geomorfologia)
Linares, Rogelio (Universitat Autònoma de Barcelona. Departament de Geologia)
Salminci, José G. (Universitat Autònoma de Barcelona. Departament de Geologia)
Gutiérrez, Francisco (Universidad de Zaragoza. Departamento de Ciencias de la Tierra)

Date:	2021
Abstract:	A historical series of aerial photographs spanning more than 70 years (1945-2018) revealed that natural acid rock drainage (ARD) has experienced an intensification in the Noguera de Vallferrera alpine catchment (Central Pyrenees) due to climate change during the last decade. ARD manifests by the precipitation of whitish aluminum-compounds that strikingly cover the beds of some gullies and streams in high-mountain catchments. The total length of affected streams has increased from ca. 5 km (1945) to more than 35 km (2018). Up to 68 water samples were collected in three main areas to determine the spatial variation in acidity and concentration of dissolved metals, representative of surface and subsurface waters. Concentration of aluminum clearly correlates with acidity of waters. Aluminum precipitation occurs where acidic waters, enriched in metals due ARD related to the oxidation of sulfides, mix with non-acidic waters. In addition to aluminum, other potentially toxic trace metals are present at concentrations well above the quality standards for natural waters. Here, we show that climate warming and the severe droughts recorded in the last decade are the most plausible causes for the observed ARD intensification. This result is supported by a good correlation between the regional ascending rate of the periglacial limits (ca. 46 m-height/decade) and the rising rate of the maximum elevations at which ARD occurs (ca. 45 to 55 m-height/decade). In addition to climatic control, we also show that the local geomorphology is playing a major role. The distribution of periglacial deposits (rock glaciers, protalus ramparts, cones and talus slopes) and deep-seated gravitational slope deformations exert a strong control on the spatial patterns and hydrodynamics of ARD. A better understanding of the phenomenon and the monitoring of its evolution can provide clues on these side effects of climate warming, here and in many other alpine catchments worldwide.
Grants:	Agencia Estatal de Investigación CGL2017-85045-P Agencia Estatal de Investigación 2017-PRCV00604
Note:	Altres ajuts: acords transformatius de la UAB
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, i la comunicació pública de l'obra, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original. No es permet la creació d'obres derivades.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Acidification ; Alt Pirineu Natural Park (Central Pyrenees) ; Climate change ; High-mountain waters ; Potentially toxic trace metals
Published in:	Science of the total environment, Vol. 778 (July 2021) , art. 146070, ISSN 1879-1026

DOI: 10.1016/j.scitotenv.2021.146070
PMID: 33711593

18 p, 14.0 MB

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