Carbon chain length distribution in n-alkyl lipids: A process for evaluating source inputs to Lake Qinghai |
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| Institution: | 1. State Key Laboratory of Loess and Quaternary Geology, IEE, CAS, Xi’an 710075, China;2. School of Human Settlement and Civil Engineering, Xi’an Jiaotong University, Xi’an 710049, China;1. Univ. Bordeaux, Laboratoire d’Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), UMR CNRS 5805, Allée Geoffroy Saint-Hilaire, 33615 Pessac Cedex, France;2. CNRS, Laboratoire d’Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), UMR CNRS 5805, Allée Geoffroy Saint-Hilaire, 33615 Pessac Cedex, France;1. DFG-Leibniz Center for Surface Process and Climate Studies, Institut für Erd- und Umweltwissenschaften, Universität Potsdam, Germany;2. MARUM-Center for Marine Environmental Sciences, Universität Bremen, Germany;3. Max-Planck-Institut für Biogeochemie, Jena, Germany;4. INRA, UR546 BioSP, Avignon, France;5. CEREGE, UMR 7730 Aix-Marseille Université, CNRS, CDF, IRD, Aix-en-Provence, France;6. Faculté des Sciences, Université de Maroua, Cameroon;7. National Herbarium of Cameroon, IRAD, Yaoundé, Cameroon;1. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, USA;2. Massachusetts Institute of Technology-Woods Hole Oceanographic Institution Joint Program in Oceanography and Applied Ocean Science and Engineering, 77 Massachusetts Avenue, Cambridge, MA 02139, USA;3. MARUM – Center for Marine Environmental Sciences, Universität Bremen, 28334 Bremen, Germany;4. Groupe de Recherche en Sciences Exactes et Naturelles/Délégation Générale à la Recherche Scientifique et Technologique (GRSEN/DGRST), Ministere de la Recherche Scientifique, Brazzaville, Congo;1. State Key Laboratory of Loess and Quaternary Geology, IEE, CAS, Xi’an 710075, China;2. School of Human Settlement and Civil Engineering, Xi''an Jiaotong University, Xi’an 710049, China;3. Department of Earth Sciences, The University of Hong Kong, Hong Kong, China;1. State Key Laboratory of Loess and Quaternary Geology, IEE, CAS, Xi’an 710061, China;2. School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an 710049, China;3. University of Chinese Academy of Sciences, Beijing 100049, China;1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China;2. CAS Center for Excellence in Quaternary Science and Global Change, Xi''an 710061, China;3. Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China |
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| Abstract: | Lake sediments generally contain a mixture of terrestrial and aquatic source inputs, and determining the major inputs is important for understanding geological records in paleoenvironment and paleoclimate research. In this study we describe the distribution of n-alkanes and n-fatty acids (FAs) in representative modern plants from around Lake Qinghai. We found a significant difference in the average length of n-FA carbon chains (ACL Fa16–32) in terrestrial (23.3) and aquatic plants (18.6). The results reveal that ACL Fa16–32 may essentially serve as a proxy for evaluating the major source inputs to lake sediments. Assessment of surface sediments from the lake showed that the FAs originated from a mixture of inputs, with the aquatic source input predominant at most sites. Additionally, the δD values of sediment mid-chain n-acids (C22) showed a relationship with the ACL Fa16–32 proxy: an increased Fa ACL corresponded to more negative hydrogen isotope ratio values. We suggest that different sources should be considered and ACL Fa16–32 could be a potential calibration proxy before using δD values to extract reliable isotopic information from lake water. More attention should be paid to source inputs and their relationship to other geochemical proxies in future studies of lake sediments. |
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