[Hydrogen and Oxygen Isotopic Compositions of Precipitation and Its Water Vapor Sources in Eastern Qaidam Basin]

Stable hydrogen and oxygen isotopes can be used as a tracer to analyze water vapor sources of atmospheric precipitation. We choose Golmud and Delingha as our study areas, Golmud locates in the south of Qaidam basin, and Delingha locates in the northeast. Based on the analysis of monthly change of hydrogen and oxygen isotopic compositions of precipitation during June to September of 2010, and the relationship between deltaD and delta18O in precipitation, we investigated the water vapor sources of precipitation in eastern Qaidam basin. The results show that: (1) meteoric water line between June to September in Golmud is: deltaD = 7.840 delta18O - 4.566 (R2 = 0.918, P < 0.001), and in Delingha is: deltaD = 7.833 delta18O + 8.606 (R2 = 0.986, P < 0.001). The slopes and intercepts of meteoric water line between June to September in both Golmud and Delingha are lower than the global average, and the intercept in Golmud is only -4.566, which indicates the extremely arid climate condition. (2) the delta18O content of precipitation is much higher in Golmud in early July, it shows the enrichment of some heavier isotopes. However, the delta18O content of precipitation becomes lower from late July to early September, especially for the late September. The 8180 content of precipitation in Delingha is higher in June to August than that in late September. (3) the water vapor sources of precipitation in Golmud and Delingha are different, Golmud area is the northern border of Qinghai-Tibet Plateau where the southwest monsoon can reach, and the southwest monsoon brings water vapors of precipitation, but the water vapors of precipitation in Delingha are mainly from local evaporation.