Assessing the ratio of archaeol to caldarchaeol as a salinity proxy in highland lakes on the northeastern Qinghai–Tibetan Plateau |
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| Institution: | 1. State Key Laboratory of Loess and Quaternary Geology, IEE, CAS, Xi''an 710075, China;2. State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China;3. Key Laboratory of Salt Lake Resources and Chemistry, Qinghai Institute of Salt Lake, Chinese Academy of Sciences, China;4. University of Chinese Academy of Sciences, Beijing 100049, China;5. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China;6. Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056, USA;7. Department of Marine Sciences, The University of Georgia, Athens, GA 30602, USA;8. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China;9. Key Laboratory of Marine Chemistry Theory and Technology (Ocean University of China), Ministry of Education/Qingdao Collaborative Innovation Center of Marine Science and Technology, Qingdao 266100, China;10. Department of Earth Sciences, The University of Hong Kong, Hong Kong, China;1. School of Earth Sciences, Zhejiang University, Hangzhou, China;2. Department of Earth Sciences, The University of Hong Kong, Hong Kong;3. State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, CAS, Nanjing, China;4. Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, USA;5. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, CAS, Xi''an, China;6. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing, China;7. University of Chinese Academy of Sciences, Beijing, China;8. Limnological Research Center, Department of Earth Sciences, University of Minnesota, Minneapolis, USA |
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| Abstract: | The ratio of archaeol to caldarchaeol (the ACE index) has been proposed recently as an index for paleosalinity reconstruction and is based principally on archaeal core lipids (CLs) from coastal salt pans (Turich, C., Freeman, K.H., 2011. Archaeal lipids record paleosalinity in hypersaline systems. Organic Geochemistry 42, 1147–1157). We have examined possible relationships between salinity and ACE in both CLs and intact polar lipids (IPLs) from suspended particulate matter (SPM) and surface sediments of lakes and surrounding soils on the northeastern Qinghai–Tibetan Plateau. Our results showed that ACE values were positively correlated with salinity in all samples; however, CL ACE values were systematically higher than IPL ACE values, probably due to different degradation kinetics of intact polar (IP) archaeol and IP caldarchaeol. On the other hand, surface sediment ACE values from both CLs and IPLs were lower than SPM ACE values, probably due to enhanced production of caldarchaeol relative to archaeol in the sediment. Our results demonstrate that the ACE proxy reflects changes in salinity in diverse environments on the Qinghai–Tibetan Plateau, which is promising for paleosalinity reconstruction; however, caution should be used when applying the salinity proxy before we have a better understanding of degradation kinetics of archaeal IPLs and in situ production of caldarchaeol and archaeol in sediments. |
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