Sulfur and oxygen isotopes of sulfate in precipitation and lakewater,Quebec, Canada |
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| Institution: | 1. Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. Department of Earth Sciences, University of Southern California, Los Angeles, CA, USA;2. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA;3. School of Geography and the Environment, University of Oxford, Oxford, UK;4. Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA, USA;5. CNRS – Institut de Physique du Globe de Paris – Université Sorbonne Paris-Cité, Paris, France;6. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA;1. Institute of Surface-Earth System Sciences, School of Earth System Science, Tianjin University, Tianjin 300072, China;2. Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, Munich 80333, Germany;3. German Research Centre for Geosciences (GFZ), Telegrafenberg 14473, Potsdam, Germany;4. Centre de Recherches Pétrographiques et Géochimiques (CRPG), Vandoeuvres-lès Nancy, France;5. Department of Geography, The University of Hong Kong, Pokfulam Road, Hong Kong, China;6. Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China;1. Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;2. CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China;3. University of Chinese Academy of Sciences, Beijing 100049, China;4. Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China |
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| Abstract: | Stable isotope ratios of sulfur and oxygen of sulfate ion in precipitation and lakewater were monitored in six headwater lakes in Québec, Canada. The lakes studied are oligotrophic and located over a wide area (350 km) on the Canadian Shield, which is known to be sensitive to acidification.The δ34S of the sulfate ion in precipitation ranges from 3.1 to 6.7‰ for all locations during the sampling period, which is very close to the values found for the lakes, from 3.5 to 6.7‰. Moreover, the δ34S of sulfate showed seasonal variations which are parallel in time for all stations. This strongly suggests that precipitation is a major source of sulfate in the lakes that were investigated. However, the δ18Ovalues of precipitation sulfate are close to each other between stations and are consistently higher (+ 8.3 to 13.5‰) than that of the lakes (+ 1.7 to 8.5‰). In addition, there is no spatial or temporal trend in lake δ18O sulfate, suggesting that a transformation occurs to sulfate in the watersheds. We suggest the hypothesis that sulfate ion is reduced and reoxidized in the runoff and lake waters so that it acquires an oxygen isotopic label different from precipitation. |
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