[Relationships between stable isotopes in precipitation in Wolong and monsoon activity]

Stable isotopic analyses with precipitation, air temperature, wind direction and wind speed were performed in the Wolong Nature Reserve from July, 2003 to July, 2004. Results showed that d-excess values were (8.4 +/- 7.4) per thousand, (- 7.4 +/- 12.5) per thousand and (12.5 +/- 12.1) per thousand in precipitation events from April to August, September to October and November to March, respectively. Stable isotopic characteristics and d-excess values indicated that precipitation was mainly brought by the East Asia monsoon from ocean surface moisture from April to August, by the Indian summer monsoon from ocean moisture which extremely affected by rainout (strong depletion of heavy isotope) from September to October, and by Westerly from inland evaporation and local evaporation from November to March. Significant negative correlations between isotopic values and precipitation, which was amount effect, were found from April to October (r = - 0.389 for deltaD and r = - 0.380 for delta18O, p < 0.05, respectively) . Temperature effect also might affect isotopic values in precipitation (p < or = 0.10). During the active period of the East Asia monsoon and the Indian summer monsoon, stable isotopes in precipitation events had significant negative correlations with south wind index (r = - 0.354 for deltaD and r = - 0.390 for delta18O, p < 0.05, respectively), indicating that isotopic values closely associated with the origin and transport of moisture, and especially the Indian summer monsoon could bring vapors with very low isotopic values and d-excess values.