[Effects of Water Vapor Source and Local Evaporation on the Stable Hydrogen and Oxygen Isotopic Compositions of Precipitation].

ABSTRACT

Stable hydrogen and oxygen isotopic compositions in precipitation are good tracers and can provide unique information about the water cycle. Precipitation samples were collected at the Nanjing, Liyang, Yixing, and Dongshan sites in 2016, and the HDO and H218O compositions of precipitation were measured. The temporal variability of HDO and H218O compositions and deuterium-excess of precipitation were analyzed, and the influence of the water vapor source and local evaporation on stable isotopic composition of precipitation were discussed. The results indicated that① Seasonal variations in the HDO composition, H218O composition, and deuterium-excess of precipitation occurred due to different water vapor sources during the summer and winter monsoon seasons. The HDO and H218O compositions were depleted during the summer monsoon season and enriched during the winter monsoon season. The deuterium-excess during the summer monsoon season was lower compared to the winter monsoon season. ② During the summer monsoon, the evaporation of Lake Taihu made the deuterium-excess of downwind precipitation and the downwind intercept of the local meteoric water line higher. During the winter monsoon season, local evaporation had little influence on HDO and H218O components in precipitation. ③ Both of the intercepts and slopes of the local meteoric water line were higher than those of the global meteoric water line, due to moisture recycling during the winter monsoon season and different water vapor sources between the summer and winter monsoon seasons.