Isotopic composition of atmospheric water vapor before and after the monsoon’s end in the Nagqu River Basin

Atmospheric water vapor samples were collected in the Nagqu River Basin in the middle of Tibetan Plateau between August and October in 2004. Results show that there exist some fluctuations of the δ18O of atmospheric water vapor, especially before and after the monsoon’s end. Moreover, the variety trend of the δ18O of atmospheric water vapor inverse correlates with that of dew point. Precipitation events make an important effect upon the variation of δ18O of atmospheric water vapor. During the whole sampling period, the δ18O values of atmospheric water vapor are low while precipitation events occurred. The moisture origins also contribute to the variation of δ18O of atmospheric water vapor. The oceanic moisture transported by the southwest monsoon results in lower δ18O of atmospheric water vapor in the Nagqu River Basin. Compared with the influence of the oceanic moisture, the δ18O values, however, appear high resulting from the effect of the continental air mass in this region.