Stable isotopic compositions of waters in the karst environments of China: Climatic implications |
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| Authors: | Hong-Chun Li Teh-Lung Ku Dao-Xian Yuan Nai-Jung Wan Zhi-Bang Ma Ping-Zhong Zhang Miryam Bar-Matthews Avner Ayalon Zai-Hua Liu Mei-Liang Zhang Zhao-Yu Zhu Ruo-Mei Wang |
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| Institution: | 1. College of Geography Sciences, Southwest University, Chongqing 400715, China;2. Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089-0740, USA;3. Department of Earth Sciences, National Cheng-Kung University, Tainan 701, Taiwan, ROC;4. Institute of Geology and Geophysics, Chinese Academy of Science, Beijing 100036, China;5. College of Earth and Environment Sciences, Lanzhou University, Lanzhou 730000, China;6. Geologic Survey of Israel, Jerusalem 95501, Israel;g Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China;h Guangzhou Institute of Geochemistry, Chinese Academy of Science, Guangzhou 510640, China |
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| Abstract: | A total of 117 water samples, including cave water, ground water, spring water and river water, collected from the monsoonal area of China have been analyzed for their H- and O-isotope composition. Overall, a δ18O–δD correlation is observed of δD = −4.45 + 6.6δ18O (R2 = 0.90) and a significant evaporation effect observed for the southern sites. Average δ18O and δD site values generally correspond to those of precipitation in nearby cities, with correlations of δD = 2.18 + 7.23δ18O (R2 = 0.95) for the sample sites and δD = 11.05 + 7.95δ18O (R2 = 0.95) for the cities. The effects of rainfall amount and temperature on precipitation δ18O were calculated using a simplified theoretical model derived from the Rayleigh distillation equation, which demonstrated that the sign of δ18Opvs. T correlation is dependent on precipitation intensity. The mean δ18O value of cave waters exhibit decreasing trends with increasing latitude and reveal a spatial pattern of positive correlation with annual mean temperature and precipitation, mainly reflecting isotopic fractionations in the moisture source traveling from the ocean side to the inland continent. This spatial pattern implies that the δ18O values recorded in the proxy climate records derived from speleothems might be influenced by shifts in monsoon boundary during the past, especially between glacial and interglacial intervals. |
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