Isotope characteristics of precipitation and identification of water vapor sources in the northern Greater Khingan Mountains, Inner Mongolia.

We investigated the water cycle and water vapor sources of precipitation in the northern Greater Khingan Mountains in Inner Mongolia, by collecting precipitation samples from June 2022 to May 2024 at the Inner Mongolia National Ecosystem Observation and Research Station. We analyzed the isotopic characteristics of precipitation and the influencing environmental factors by the backward trajectory model, potential source contribution analysis, and concentration weighted trajectory analysis, and explored water vapor sources and the potential evaporation source areas across different seasons. The results indicated that the isotopic composition of precipitation showed significant seasonal variation, with enrichment in the warm season and depletion in the cold season. The slope of the local meteoric water line (7.82) was lower than that of the global meteoric water line, and that of the shelterwood forest (6.57) was lower than the primary forest (7.39), suggesting precipitation in the shelterwood forest was more significantly influenced by secondary evaporation. During the research period and in the cold season, the temperature effect in precipitation was significant, with correlation coefficients of 0.85 and 0.94, while the effect of precipitation amount was not significant. In the warm season, water vapor sources of precipitation primarily originated from the westerly winds (48.9%) and terrestrial evaporation (31.9%), and it predominantly came from westerly winds (66.9%) and Arctic Ocean moisture (42.9%) in the cold season. The potential evaporation source regions during the warm season were mainly located in the northwest, north, and southeast of the study area, while in the cold season, they concentrated in the northwest and north.