Trace Metal Legacy On Mountain Aquatic Ecogeochemistry

Informations

Funding country

France

Acronym

TRAM

URL

-

Start date

10/1/2015

End date

-

Budget

272,017 EUR

Fundings

Abstract

Following the onset of the industrial revolution and the use of fossil energy, humans can now indisputably be seen as major geological agents. At present, anthropogenic fluxes of up to 62 chemical elements surpass their corresponding natural fluxes. Due to their geological features mountain environments have been exploited since the beginning of metallurgy. The Pyrenees are no exception as many mining sites in the region have been dated back to the Bronze Age thus allowing a potential human impact on the environment on millennial scales. Furthermore, high altitude soils are often shallow and thus susceptible to erosional processes. The mountain critical zone is therefore sensitive to human-induced environmental changes - e.g. agriculture, mining, clear cutting, as well as to impact of long-term climate change and associated rapid environmental changes. For example, flooding can remobilize trace metals stored in soils and mining heaps and impact downstream natural, agricultural but also coastal ecosystems. Peatlands, a reoccurring ecosystem in mountainous environments, acts as reservoirs of organic matter. Due to peats ability to retain trace metals and radionuclides these natural environments can be considered as a pollutant “sponge” which have accumulated contaminants since the beginning of the metallurgy and have acted as natural filters for toxic elements (e.g. Arsenic, mercury or lead) since the last deglaciation. Based on previous results on trace metal concentrations in the Central Eastern Pyrenees (Le Roux & Claustres, unpublished), we estimate that more than 600 tons of anthropogenic Pb is stored in peatlands and organic soils but also in lake sediments on the northern slope of the Pyrenees. Similar conclusions can be drawn for other metals. The fate of these potentially harmful trace elements (PHTE; i.e. Pb, Sb or Hg) in relation to long-term climate change or rapid environmental changes is poorly understood. Once these elements are remobilized within the critical zone, the catchment can become highly enriched in the bioavailable fraction of these PHTE (exceeding the recommended guideline values). Several PHTE could also be bio-accumulated in fish and other river biota, modify benthic communities and affect the quality of domestic water. The legacy of trace metal stocks in the mountain critical zone is poorly understood and the Pyrenees provide a perfect mountain range for detailed scientific investigations of the fate and the impact of those PHTE on the ecological functioning of mountain catchments. As a response to the 2015 ANR panel’s call for a better understanding of the critical zone, ecosystems (both Axe 1), ecotoxicology (Axe 2) , TRAM is in our opinion a promising interdisciplinary and integrative project to face the different following challenges: 1) TRAM will assess changes in the introduction and transfer of PHTE over Millenia using innovative geochemical and isotopic tracers, 2) TRAM will further combine a geochemical approach with ecological analyses to define the impact of PHTE on biodiversity and ecosystem services, 3) TRAM will develop a range of indicators to make the impact of PHTE on the mountain critical zone clearer to decision makers and stakeholders, considering also hydrological, biogeochemical modelling and GIS analyses.