チベット高原の天然水の同位体組成とその由来について

抄録

Oxygen and hydrogen isotope compositions (δ¹⁸O and δD) of natural waters can provide useful meteorological and hydrological information. In the present study, oxygen and hydrogen isotope compositions of snow samples from Mt. NAMUNANI (7,694m) and river water samples in Tibetan Plateau were analyzed to deduce sources of the water supplied to Tibetan Plateau. The following conclusions were obtained from isotopic result and d-excess parameter (d=δD-8•δ¹⁸O) which is useful as an index of the source of water vapor mass. 1) In Tibetan Plateau, oxygen and hydrogen isotope compositions of river waters depend on the altitude and on the extent of contribution to surface waters of different water vapor masses (whose sources are different such as Indian Ocean in the monsoon season, the Western areas such as the Mediterranean Sea in the premonsoon, and so on). 2) The d-excess parameters of river waters became larger and δ¹⁸O and δD values heavier with increasing latitude. This fact indicates that the contribution to surface waters of monsoon water vapor mass (smaller d value and lighter δ¹⁸O and δD values) from Indian Ocean becomes smaller with increasing latitude.