Objective  To study the characteristics of hydrogen and oxygen stable isotope in precipitation and the source of regional atmospheric precipitation in wetland forest area of Tangpu reservoir and to provide reference information for water resource conservation and management by clarifying quantitatively the distribution and transformation of precipitation in the process of hydrologic cycle in the forest ecosystem of the Kuaijishan-Tangpu reservoir transition zone.

Method  In this study, the data of hydrogen-oxygen isotope in 166 atmospheric precipitation samples obtained from July 2015 to July 2017 in the Tangpu reservoir wetland forest were analyzed by using isotope technology to examine the composition of hydrogen and oxygen stable isotope and to clarify the relationship between the composition and environmental factors (precipitation and temperature). The source and migration path of water vapor were determined by simulating the air mass transmission pathway based on backward trajectory method of the HYSPLIT model.

Result  The relational expression of δD and δ¹⁸O in atmospheric precipitation in the wetland forest area of Tangpu reservoir was δD = 8.36δ¹⁸O+14.92 (R² = 0.966, n = 166, P < 0.01); the value of δD in precipitation ranged from -147.52‰ to 2.71‰, with the average value was -38.13‰±27.61‰; the value of δ¹⁸O ranged from -19.05‰ to -1.17‰, with the average value was -6.34‰±3.24‰, and the values changed significantly among seasons. The value of excess deuterium (12.61‰) was higher than the global average (10‰), and a seasonal pattern of excess deuterium in atmospheric precipitation with low value in wet season and high value in dry season was found. The "temperature effect" was not obvious whereas the "precipitation effect" existed significantly.

Conclusion  The meteoric water line of the wetland forest is different from the global meteoric water line and China meteoric water line, The values of δD and δ¹⁸O in atmospheric precipitation follows obvious seasonal variation in this area. The seasonal change of the water vapor sources of atmospheric precipitation is obvious. It is concluded that the meteoric water vapor is mainly from the inland areas in dry season (from October to April of the following year), while it mainly comes from the western Pacific and the Indian Ocean in wet season (from May to September) according to hydrogen and oxygen isotopic value in precipitation, excess deuterium, and the results of trajectory simulation.