Characteristics of atmospheric precipitation isotopes and isotopic evidence for the moisture origin in Yushugou River basin, Eastern Tianshan Mountains, China

Abstract

Based on the variations in stable hydrogen and oxygen isotope ratios (δD and δ18O) of precipitation and NCEP/NCAR (National Centers of Environmental Prediction/National Center for Atmospheric Research) re-analysis data, we investigated the characteristics of the precipitation isotopes and the moisture origin during spring and summer seasons (from May to August) in the Yushugou River basin, East Tianshan Mountains. The more negative δ18O and higher d-excess values in spring and more positive δ18O and lower d-excess values in summer indicated the different moisture sources and temperature effects on isotope variations. By studying the meteoric water line, we found that the slope and intercept of local meteoric water line (LMWL) were lower than the global meteoric water line (GMWL) and China LMWL, which indicated arid climate. The temperature effect of δD and δ18O in precipitation was obvious with correlation coefficients of 0.41 and 0.48, respectively, and there was no rainfall effect. The research of water vapor transfer showed that the moisture origin was predominantly from westerly air masses during the observation period. δ18O and d-excess values variations in precipitation and the HYSPLIT4.0 air mass trajectory model suggested that there were accidental events, and sometimes the moisture was from drier polar air masses during the spring.