[Stable Isotopes of Precipitation in the Eastern Tarim River Basin and Water Vapor Sources]

The in-situ monitoring of stable hydrogen and oxygen isotopes (δ¹⁸O and δ²H) in precipitation is helpful to understand the processes of water phase change, mixing, and transportation. Due to the arid climate in the eastern Tarim River basin, water resources are the key factor affecting the regional sustainable development. However, the understanding of stable hydrogen and oxygen isotopes in precipitation is still limited for this region. Based on the isotope data of 103 precipitation samples collected at four stations in the eastern Tarim River basin from June 2019 to September 2020, the spatial and temporal characteristics of stable hydrogen and oxygen isotopes in precipitation were analyzed, and the connections between stable isotopes and moisture sources were discussed. The findings provide a reference for the application of environmental isotope tracers in arid areas. The results show that, ① the four sampling stations generally presented an increasing trend in precipitation stable isotopic values from north to south, and the isotopic values were higher in summer and lower in winter. The d-excess value in the study region was smaller than the national average, and the slope of the local meteoric water line exhibited a significant arid characteristic. ② There was a positive correlation between precipitation stable isotopes and air temperature in the study region, whereas a weak negative relationship was seen between d-excess and air temperature. The negative correlation occurred between δ¹⁸O and relative humidity, and the d-excess value exhibited a positive correlation with relative humidity. ③ The backward trajectory showed that the eastern Tarim River basin is mainly controlled by the westerlies paths. The proportion of air mass that comes from the middle and short distance is relatively large. The concentration weighted trajectory method showed that the farther from the precipitation sampling site, the more stable the d-excess value was. The closer to the sampling site, the more frequently the concentration changed, indicating that the d-excess value was greatly affected by the local water vapor recycling.