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Mountain lakes, indicators of pollution caused by human activity


In her doctoral thesis, researcher Montserrat Bacardit has studied mountain lake basins. Despite being almost inaccessible, some lakes and its basins are clearly polluted and contain potentially toxic elements for these ecosystems.

Trace elements –a term which includes several metals and metalloids- are natural constituents of the Earth and the concentration of each of them is different in air, rocks, sediments, soil and alive organisms of all geographic areas.

Since old civilizations times, human activities have interfered with natural biological, geological and chemical cycles of trace elements. Despite being inaccessible and remote, mountain lake basins are clearly polluted by trace elements coming from anthropogenic emissions that have reached these areas through long-range atmospheric transport and subsequent deposition.

Remote Ecosystems

Mountain lakes and their basins are excellent indicators of this long-range pollution. Its continuous accumulation has left a significant amount of potentially toxic trace elements in these relatively remote ecosystems.

The thesis of Montserrat Bacardit (Centre for Advanced Studies of Blanes, CSIC), conducted by Dr. Lluís Camarero and supervised by Girona University researcher Dr. Sergi Sabater, focuses on the biogeochemistry of a group of environmentally relevant trace elements (Ni, Cu, Zn, As, Se, Cd and Pb) in some Pyrenees’ lake basins, with a special emphasis on distinguishing “natural” components from “anthropogenic” contributions. In addition, five other metals have been studied (Al, Fe, Ti, Mn, Zr), in order to determine natural biogeochemical flows and processes in lake systems.


Guards of atmospheric pollution

Bacardit has carried out direct measurements of current atmospheric flows of major and trace elements. In this study, predominant meteorological factors have been linked to elementary deposition flows. In another study, seasonal atmospheric flows of major and trace elements have been estimated by sampling the winter snow pack along an altitude gradient.

On the basis of these two studies, the researcher concludes that concentrations of airborne trace elements in Central Pyrenees can be considered as representative of the background pollution levels in remote areas of Europe.

Moreover, measurements of five other high mountain catchments in Europe have been obtained in order to compare them. Elements such as Al, Ti, Fe, Mn and As are part of the dust transported from the Iberian Peninsula and north Africa and episodically arriving in larger amounts in the Pyrenees, and in smaller amounts in other European high mountain areas located further north. On the other hand, the highest concentrations of Pb, Zn, Ni, Cu, As and Cd have been found in the Tatra mountains, in the Ticino region and in Piedmont –showing a stronger influence of these regions’ industry and urban areas-, the lowest, in the Tyrol, and medium concentrations have been found in the Pyrenees and in the Grampian Mountains.

 

A risk for ecosystems protection

The researcher has examined the long-term historical deposition in the Pyrenees by means of registers in soils and lake sediment evidence. Concentrations of trace elements in the Pyrenees’ soils are comparable to registers in soils of other mountain areas in Europe and, in many cases, they exceed the limits recommended for ecosystems protection.

Moreover, inventories (concentrations per unit area) of anthropogenic origin trace elements that have been measured on the whole lake basin are three orders of magnitude larger than current annual atmospheric flows in the Pyrenees. This result highlights the potential of sediments and soils as sources of delayed pollution in the long term if possible environmental changes favour remobilization of anthropogenic trace metals that have been accumulated through time.

In her thesis, Trace element biogeochemistry in high mountain lake catchments: identifying anthropogenic versus natural components from the atmospheric contamination legacy in remote natural areas, Montserrat Bacardit justifies the need to carry on with observations in many other mountain catchments. According to the researcher, it would also be necessary to carry out a long term integrated observation of atmospheric deposition, river and lake transport, sediment flow, and incorporation of trace elements in mountain basin vegetation. 

PHOTO: Estahn Redon (Vall d’Aran)


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Proyecto financiado por el Ministerio de Educación, Cultura y Deporte en el marco del Programa Campus de Excelencia Internacional

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