International audiencePerfluoroalkyl compounds (PFCs) and total mercury (THg) were investigated in fish liver collected from four high-mountain lakes in the French alps in which the water was fed only by atmospheric deposition. Concentrations of various PFCs, including C9-C15 perfluoroalkyl carboxylates (PFCAs) and perfluorooctane sulfonate (PFOS) were quantified. The PFOS concentration was similar in all high-mountain lakes with mean concentrations ranging from 3.61- 4.24 ng g1 wet weight (ww) indicating homogeneous atmospheric deposition. Conversely, the spatial distribution of PFCAs and THg was strongly influenced from a different emission source, which is probably the city of Grenoble, which resulted in significantly higher concentration levels of PPFCAs in three lakes (Po0.001) and of THg in two lakes (Po0.05) located easterly from Grenoble. Furthermore, the positive correlation between PFCAs and THg suggest similar transport and bioaccumulation pathways. The contribution of the longer chain PFCAs decreased with increasing distance from the local source area of Grenoble, which could be attributed to their less pronounced transport potential. Results from this study demonstrate that the contamination of PFCs and THg in the fish of the high-mountain lakes originated from atmospheric deposition and subsequent bioaccumulation

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The present study proposes a technological transfer from modern mining prospection to the field of archaeology, providing a methodology to facilitate the discovery of ancient mining sites. This method takes advantage of the thousands of geochemical analyses of streambed sediments, performed by national geological surveys to inventory mineral substances. In order to delineate geochemical anomalies, the datasets are treated following two different approaches: Exploratory Data Analysis and a fractalbased method often recognised as more powerful. Mineral prospectivity maps are then obtained by combining the results with a geographical information system. The surroundings of the Celtic oppidum of Bibracte, French Massif Central, known to have been mined at least since the Late Bronze Age until Modern Times, have been chosen to exemplify the method's potential in archaeology. First, an exhaustive record of the mining sites was undertaken over a pilot area by pedestrian prospection. If mineral prospectivity maps had been used as guidelines, w70% of these mines would have been discovered by prospecting only w15e20% of the whole area whatever the method used to treat the dataset. At least for our specific case, the multifractal approach is as powerful as EDA. Besides saving a significant amount of time and effort, the methods described here may supply clues for determining the nature of mineral substances exploited in the past, when such information cannot be straightforwardly obtained from the field or from textual archives. It should however be noticed that this approach is proposed as a first step before peer archaeological investigation following more conventional methods. Technically, there is no real obstacle to the application of the methodology proposed here, because (i) software and associated packages are freely available from the web, as well as original geochemical datasets (at least in France), and (ii) minimal mathematical skills are required.Ó

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Total mercury (THg) and methylmercury (MeHg) concentrations were measured in the muscle of Arctic charr (Salvelinus alpinus) and in the water column of 4 lakes that are located in the French Alps. Watershed characteristics were determined (6 coverage classes) for each lake in order to evaluate the influence of watershed composition on mercury and methylmercury concentrations in fish muscle and in the water column. THg and MeHg concentrations in surface water were relatively low and similar among lakes and watershed characteristics play a major role in determining water column Hg and MeHg levels. THg muscle concentrations for fish with either a standardized length of 220mm, a standardized age of 5 years or for individualuals did not exceed the 0.5mg kg(-1) fish consumption advisory limit established for Hg by the World Health Organization (WHO, 1990). These relatively low THg concentrations can be explained by watershed characteristics, which lead to short Hg residence time in the water column, and also by the short trophic chain that is characteristic of mountain lakes. Growth rate did not seem to influence THg concentrations in fish muscles of these lakes and we observed no relationship between fish Hg concentrations and altitude. This study shows that in the French Alps, high altitude lakes have relatively low THg and MeHg concentrations in both the water column and in Arctic charr populations. Therefore, Hg does not appear to present a danger for local populations and the fishermen of these lakes.

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The impact of ponds on basins has recently started to receive its well-deserved scientific attention. In this study, pond-induced impacts on soil erosion and sediment transport were investigated at the scale of the French Claise basin. In order to determine erosion and sediment transport patterns of the Claise, the Coordination of Information on the Environment (CORINE) erosion and Soil and Water Assessment Tool (SWAT) models were used. The impact of ponds on the studied processes was revealed by means of land cover change scenarios, using ponded versus pondless inputs. Results show that under current conditions (pond presence), 12.48% of the basin corresponds to no-erosion risk zones (attributed to the dense pond network), while 65.66% corresponds to low-erosion risk, 21.68% to moderate-erosion risk, and only 0.18% to high-erosion risk zones. The SWAT model revealed that ponded sub-basins correspond to low sediment yields areas, in contrast to the pondless sub-basins, which yield appreciably higher erosion rates. Under the alternative pondless scenario, erosion risks shifted to 1.12%, 0.52%, 76.8%, and 21.56% for no, low, moderate, and high-erosion risks, respectively, while the sediment transport pattern completely shifted to higher sediment yield zones. This approach solidifies ponds as powerful human-induced modifications to hydro/sedimentary processes.