Climate change enhances the mobilisation of naturally occurring metals in high altitude environments

Abstract

Graphical abstract: Catchment of Lake Respomuso in the central Pyrenees (Spain) experiencing increased metal mobilization due to climate change effects, including an increase in spring freezing level.Author copy. Published in Science of the Total Environment 04/2016; 560-561: 73-81 2 AbstractManmade climate change has expressed a plethora of complex effects on Earth's biogeochemical compartments. Climate change may also affect the mobilisation of natural metal sources, with potential ecological consequences beyond mountains' geographical limits; however, this question has remained largely unexplored. We investigated this by analysing a number of key climatic factors in relationship with trace metal accumulation in the sediment core of a Pyrenean lake. The sediment metal contents showed increasing accumulation trend over time, and their levels varied in step with recent climate change. The findings further revealed that a rise in the elevation of freezing level, a general increase in the frequency of drier periods, changes in the frequency of winter freezing days and a reducing snow cover since the early 1980s, together are responsible for the observed variability and augmented accumulation of trace metals. Our results provide clear evidence of increased mobilisation of natural metal sources -an overlooked effect of climate change on the environment. With further alterations in climate equilibrium predicted over the ensuing decades, it is likely that mountain catchments in metamorphic areas may become significant sources of trace metals, with potentially harmful consequences for the wider environment.

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

“…This supports the hypothesis that trace metals of geological origin can become concentrated in rock glacier outlets due to a set of physical and chemical processes operating in permafrost, such as enrichment related to higher water residence time (Esposito et al, 2016) and different groundwater paths (MacLean et al, 1999;Frey and McClelland, 2009), freezing-thaw cycles (Williams et al, 2006;Thies et al, 2007Thies et al, , 2013, or acid rock drainage (ARD) induced by sulphide oxidation on freshly exposed rocks (Todd et al, 2012). In addition, the fact that only Al, Mn and Fe reached higher levels in glacier-fed than in permafrost-fed waters in each catchment agrees with recent observations that the mentioned processes are not exclusive of permafrost, but can occur also in other high-altitude systems in relation to climate warming (Zaharescu et al, 2016). The present study did not provide further elements on the possible mechanism controlling trace metal enrichment in Alpine headwaters, as no relation was found with possible regulating factors, such as water pH or particulate matter.…”

Riparian ecosystem in the alpine connectome. Terrestrial-aquatic and terrestrial-terrestrial interactions in high elevation lakes

“…Lake and riparian sediments at high elevations are generally dominated by catchment bedrock denudation products, and autochthonous organic matter fixation (Zaharescu et al, 2009 and2015a). Results of the MFSO of riparian vegetation composition against sediment nutrients, major and trace elements contents resulted in a bi-dimensional solution, with Mg and Pb able to reliably predict the vegetation composition (cumulative r =0.74; Table 3, Fig.…”

“…Climatological variations such as the type and intensity of precipitation, daily temperature variation, frequency of 0ºC temperatures and the duration of freezing (Keller et al, 2005), as well as variation in these factors with slope orientation and altitude, have been shown to affect the distribution of plant cover over localized areas (Baker, 1989). Effects of climate change, including changes in precipitation, air temperature/ freezing line and snow cover (Zaharescu et al, 2015a), catchment hydrology and lake temperature and mixing (Thompson et al, 2005) are expected to greatly influence the thermodynamics and geochemistry of high altitude catchments, and consequently their lake and riparian communities. Evidence has shown considerable climate change related upward shift in mountain biome, with visible consequences on catchment hydrology, climate and geochemistry (Parker et al, 2008, Thompson et al, 2005.…”

“…can affect their distribution through effects on their physical drivers, including precipitation, freezing line, hydrology and weathering fluxes(Zaharescu et al, 2015a).…”

Ecosystem shifts in Alpine streams under glacier retreat and rock glacier thaw: A review

“…In addition, climatic changes (e.g. more frequent dry periods, reduced snow cover) are capable of enhancing the mobilization of naturally-occurring trace metals through enhanced weathering processes in glacier-free areas, as detected in the Pyrenees (Zaharescu et al, 2016). This may cause high loads of trace elements to freshwaters, even when deglaciation has finished.…”