Peculiar arsenic, copper, nickel, uranium, and yttrium-rich stone coatings in a high mountain stream in the Austrian Alps

Abstract

Peculiar coatings rich in arsenic, copper, nickel, uranium, and yttrium were found to cover stones in a high mountain stream downstream of the confluence of small acidic tributaries, which emerge at the front of the Krummgampen rock glacier (Ötztal Alps, Tyrol, Austria). The hard mineral coatings are characterized by a white color, a x-ray amorphous structure and showed properties of hydrous aluminium silicates like allophane (Al O (SiO ) x n H O) and/or imogolite (Al SiO (OH) ). Main constituents of the coatings are aluminium, silica, and sulfur. Contrary to high concentrations of arsenic, copper, nickel, uranium, and yttrium in the stream stone coatings, corresponding element values are below the limit of detection both in the Krummgampen stream and -except for nickel and traces of copper -also in acidic outflows from the rock glacier. Stone coatings are neither present in rock glacier outflows nor in the Krummgampen stream upstream of the rock glacier, nor in other streams in the catchment. The coatings are interpreted as a precipitate on or an accretion to stone surfaces in the Krummgampen stream, which is characterized by moderate solute concentrations and a neutral pH. In acidic outflows of the rock glacier high concentrations of dissolved sulfate, calcium, magnesium, silica, aluminium, manganese, and nickel prevail. Some constituents of stream stone coatings like arsenic, copper, nickel, uranium, and yttrium have also been measured in paragneiss rocks in the catchment of the rock glacier which are characterized by heavily weathered accessory minerals monazite, xenotime, and pyrite. It is therefore very likely that minerals which occur in the bedrock of the catchment represent a major source for elements accumulated in stream stone coatings even though processes like element release from the ice-rock matrix in the rock glacier, transport to and accumulation on Krummgampen stream stone surfaces are not yet completely understood.____________________________________________________

Diatom diversity in headwaters influenced by permafrost thawing: First evidence from the Central Italian Alps

“…However, the knowledge on the impact of climate change on permafrost thawing processes, and, consequently, on the chemical and biological quality of headwaters emerging from Alpine rock glaciers is still scarce (Colombo et al, 2018). Despite the limit posed by the small number of headwater surveyed, the present study confirms the results obtained by previous investigations on chemical features and biodiversity of permafrost-fed headwaters waters in the Central Alps (Thies et al, 2007(Thies et al, , 2013(Thies et al, , 2018Ilyashuk et al, 2014;Lösch et al, 2015;Thaler et al, 2015), and provides new insight on aspects scarcely considered so far.…”

“…Despite the expected change in the relative importance of the major components of the Alpine cryosphere, the understanding of the possible cascading effects of permafrost degradation on water quality and ecology of Alpine freshwater is still largely incomplete. Insights into the effects of rock glacier thawing on inorganic chemistry of Alpine headwaters were provided by some recent case studies (Krainer et al, 2007;Thies et al, 2007Thies et al, , 2013Thies et al, , 2018Colombo et al, 2018a;Engel et al, 2018). Compared to waters fed by glacier melt or atmospheric precipitation and groundwater, headwaters emerging from active rock glaciers are commonly characterised by higher electrical conductivity (EC) and concentration of major ions, in particular Mg 2+ , Ca 2+ and SO 4 2- (Colombo et al, 2018b).…”

Climate Change-Induced Changes in the Chemistry of a High-Altitude Mountain Lake in the Central Alps

“…With respect to the origin of the SO 4 discharged by rock glaciers, most studies hypothesized oxidation of sulfide (Ilyashuk et al 2018;Williams et al 2006;Thies et al 2017) or dissolution of gypsum generated by sulfide oxidation (Lecompte et al 2008), because of the ubiquitous presence of pyrite in metamorphic rocks. Discharge of SO 4 as a consequence of gypsum or anhydrate dissolution has been reported less frequently (Colombo et al 2019;Rogora et al 2020).…”

Water supply in times of climate change—Tracer tests to identify the catchment area of an Alpine karst spring, Tyrol, Austria

“…This extension could explain the observed discharge rates and temperatures at the Tuxbachquelle. Hydrological studies in other Alpine regions showed that rock glaciers can impact the water quality extensively and can yield a base runoff of 70 to 100 L/s during summer months (Nickus et al 2015;Thies et al 2013Thies et al , 2017Engel et al 2019).…”