Project

Discipline

ice and sediment records; automated microscopy and image analysis; lacustrine sediments; heavy metal pollution; microbial activity; Antibiotic resistant bacteria; Trace elements; Climate changes; Switzerland

Lead
Lay summary
The investigation of sediment cores from two of the largest freshwater lakes from Western Europe (lakes Geneva and Lucerne) demonstrated that natural sources of trace elements dominated before the European industrial revolution. The heavy metal pollution (e.g. lead, mercury) highly increased following the industrialization of Switzerland after 1850. The implementation of wastewater treatment plants (WWTPs) in the 1960s significantly decreased the metal pollution at the deepwater sites. By contrast, the Vidy Bay of Lake Geneva where are released the WWTP of the city of Lausanne since 1964 was highly contaminated by heavy metals due to the WWTP emissions. Lead isotopic composition furthermore highlighted the industrial pollution sources over the last 200 years. During the twentieth century, industrial releases multiplied by 10 times heavy metal fluxes to hydrological systems located on both sides of the Alps. The remote and small high altitude lake Meidsee (2661 m a.s.l. in the Southwestern Alps) revealed the strong increase in anthropogenic trace metal deposition during the Greek and Roman Empires (ca 300 BC to AD 400), the Late Middle Ages (ca AD 1400), and the Early Modern Europe (after ca AD 1600). The greatest increases in anthropogenic metal pollution were evidenced after the industrial revolution of ca AD 1850, especially in Lake Lucerne where industrial activities and the steamboat navigation released high amounts of fossil fuel combustion residues and heavy metals. The elemental and isotopic composition of sedimentary organic matter from the high-altitude Lake Meidsee provided additional information about the high-altitude Alpine landscape evolution since the Late Pleistocene/Holocene deglaciation in the Swiss Southwestern Alps; and indicated the predominant deposition of algal-derived organic matter with limited input of terrestrial organic matter before the Holocene Climatic Optimum (between 7.0 and 5.5 years ago). This research also investigated faecal indicator bacteria (Escherichia coli and Enterococcus), multiple antibiotic resistant and antibiotic resistance genes, in sediment profiles from different parts of Lake Geneva (Switzerland) over the last decades. Results showed that the WWTP input constituted the main source of pollution for several contaminants, including heavy metals, antibiotics, and antibiotic-resistant bacteria. The Bay of Vidy of Lake Geneva can therefore be considered as a reservoir of bacteria multiple resistance genes. Hence, the human-induced eutrophication in the 1970s highly enhanced the sediment microbial activity, and therein the spreading of antibiotic resistant bacteria and genes in this aquatic environment used to supply drinking water in a highly populated area.

Direct link to Lay Summary

Last update: 21.02.2013

Active participation

Number	Title	Start	Funding scheme

Although many progresses have been made during the last decade for reconstructing the European climate, there is no clear agreement among the existing reconstructions for the pre-instrumental period and this lack of knowledge hinders reliable climatic predictions (IPCC 2007). The original scientific approach in the frame of this project will address the issues of 1) The calibration of the data measured from different climatic archives (sediment and ice cores), 2) The cross-fertilization of new environmental markers providing precise tools for dating those archives, and 3) The physical and chemical characterization of the airborne minerals that were transported to Europe, in regards to past atmospheric circulation changes and anthropogenic human disturbances.This research project aims to analyze an Alpine ice core (Glacier Colle Gnifetti) and two lacustrine sediment cores (Lake Lucerne and Lake Schwaerze) with the same analytical methods. The reconstruction of the natural (aeolian dust) and anthropogenic (fossil fuel combustion) mineral aerosols emissions will provide valuable data for reconstructing the atmospheric (climatic) changes that occurred in Central Europe over the last two millennia on seasonal to decadal time scale. In fact, the transport of mineral aerosols toward the Alps is primarily influenced by the southwesterly dust laden winds from the Sahara, i.e., by the large-scale atmospheric circulation through the North Atlantic Oscillation (NAO)-like variability. The characterization of the airborne minerals entrapped in European climatic archives therefore offers a unique possibility for 1) reconstructing past atmospheric circulation changes, but also for 2) understanding the recent increase in the continental dust flux recorded at high altitude in the Alps, and the possible relationships with the unusual positive phases of NAO observed during the last decades; and for 3) estimating the proportion of the fossil fuel combustion material in the total mineral aerosol emissions supplied to the atmosphere.In order to identify the origin of the mineral dust, sophisticated mineral analyses will be performed using the state-of-the-art material available at the Section of Earth Sciences of the University of Geneva: Raman spectroscopy, ICP-MS, X-ray diffraction (XRD), X-ray micro-fluorescence (uXRF), mass spectrometer (Sr and Nd isotopes), electronic microscope, and automated transmitted light microscope. The characterization of the dust horizons in the high-altitude (Glacier Colle Gnifetti, 4450 m asl) ice-core will allow to decipher the same aeolian events in the low (Lake Lucerne, 434 m asl) and middle (Lake Schwaerze, 2780 m asl) altitudes sediment cores, and to further extend the dust record to the last millennia and to the last decades, respectively. The mineral study of Lake Lucerne sediments will be also used for reconstructing the paleohydrological regional changes (periods of drought and overflow of Lake Lucerne) that occurred in Central Switzerland during the Medieval Warm Period, the Little Ice Age, and the Modern Period on decadal resolution; and for identifying some differences in the crystalline phases produced by the successive high temperature combustion of wood, coal and oil during the steamboat navigation. Finally, this study will provide a new automated image analysis technique, calibrated with geochemical and mineral data, for analyzing/characterizing natural and anthropogenic aerosol emissions/sources in the modern environment and in climatic archives.