Trace elements in alpine and arctic lake sediments as a record of diffuse atmospheric contamination across Europe

Abstract

1. We surveyed the distribution of several trace elements in contemporary and preindustrial sediment s in 275 lakes in alpine and arctic lake districts across Europe including the Pyrenees, Alps, the Rila Mountains, Retezat, Julian Alps, Tatras, Scottish mountains, Central Norway and Greenland. 2. Sediment cores were collected at the deepest part of each lake and analysed at two depths (surface sediment and at 15–17 cm depth) for Ti, Pb, Cd, Zn, Cu, As, Hg and Se. 3. The concentrations of trace elements found in the lakes included in the survey are comparable to those reported in aquatic sediments receiving higher contamination loads. With the exception of Greenland, a large percentage of lakes showed enrichment factors for most elements well above 1.5, indicating atmospheric contamination. The influence of contamination has increased the co-distribution of trace elements in sediments, with the exception of As. 4. Pb is the element that shows the highest contamination level at the European scale, followed by Hg and As. Zn, Cd, Cu and Se contamination is detectable to a lower degree. 5. The Tatra Mountains and Scotland seem to be most affected. Natural mechanisms leading to the formation of highly organic, metal-binding sediments may be the cause of the high levels in Scotland, whereas those in the Tatras appear to be due to elevated deposition. 6. The Retezat and Central Norway appear to be least polluted. 7. In the Alps, enrichments in Pb, Hg and Zn are higher in southern than in central areas suggesting a flux of these pollutants from the south. In the Pyrenees, the high natural levels of As are remarkable. Metal enrichments in the Rila Mountains are comparable to those in the Tatras, but concentrations are much lower. 8. In general terms, the increase in trace elements in modern with respect to pre-industrial sediments reflects the history of a long range contamination affecting the remotest locations in Europe.