Author's personal copy A high-resolution historical sediment record of nutrients, trace elements and organochlorines (DDT and PCB) deposition in a drinking water reservoir (Lake Brêt, Switzerland) points at local and regional pollutant sources Florian Thevenon a,⇑ , Luiz Felippe de Alencastro b , Jean-Luc Loizeau a , Thierry Adatte c , Dominique Grandjean b , Walter Wildi a , John Poté a a Institute F.-A. Forel, University of Geneva, Versoix, Switzerland b Central Environmental Laboratory (GR-CEL), Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland c Institut des Sciences de la Terre, University of Lausanne, Switzerland highlights " Doubling terrigenous element content following the artificial rise of the lake in 1922. " Low enrichment in heavy metal but additional agricultural contribution to copper. " Continuous increase in organic matter (P, C org , N) over the last 60 years. " High resolution record of atmospheric deposition of DDT and PCB in Switzerland. " Impact of atmospheric deposition and watershed runoff on drinking water quality. graphical abstract article info Article history: Received 3 May 2012 Received in revised form 29 October 2012 Accepted 4 November 2012 Available online 28 November 2012 Keywords: Sediments Drinking water reservoir Trace elements Organochlorines Organic matter abstract The 137 Cs and 210 Pb dating of a 61-cm long sediment core retrieved from a drinking water reservoir (Lake Brêt) located in Switzerland revealed a linear and relatively high sedimentation rate (1 cm year 1 ) over the last decades. The continuous centimeter scale measurement of physical (porewater and granulome- try), organic (C org , P, N, HI and OI indexes) and mineral (C min and lithogenic trace elements) parameters therefore enables reconstructing the environmental history of the lake and anthropogenic pollutant input (trace metals, DDT and PCBs) at high resolution. A major change in the physical properties of the lower- most sediments occurred following the artificial rise of the dam in 1922. After ca. 1940, there was a long- term up-core increase in organic matter deposition attributed to enhance primary production and anoxic bottom water conditions due to excessive nutrient input from a watershed predominantly used for agri- culture that also received domestic effluents of two wastewater-treatment plants. This pattern contrasts with the terrigenous element input (Eu, Sc, Mg, Ti, Al, and Fe) which doubled after the rising of the dam but continuously decreased during the last 60 years. By comparison, the trace metals (Cu, Pb and Hg) pre- sented a slight enrichment factor (EF) only during the second part of the 20th century. Although maxi- mum EF Pb (>2) occurred synchronously with the use of leaded gasoline in Switzerland (between ca. 1947 and 1985) the Hg and Cu profiles exhibited a relatively similar trend than Pb during the 20th cen- tury, therefore excluding the alkyl-lead added to petrol as the dominant (atmospheric) source of lead input to Lake Brêt. Conversely, the Cu profile that did not follow the decrease registered in Pb and Hg dur- ing the last 10 years, suggests an additional source of Cu probably linked to the impact of agricultural 0045-6535/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2012.11.002 ⇑ Corresponding author. Tel.: +41 22 379 03 15; fax: +41 22 379 03 29. E-mail address: Florian.Thevenon@yahoo.fr (F. Thevenon). Chemosphere 90 (2013) 2444–2452 Contents lists available at SciVerse ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere