Moisture source identification based on the seasonal isotope variation of precipitation in the Poyang Lake Wetland, China

Abstract

Study region: The wetland ecosystem of Poyang Lake, the largest freshwater lake in China. Study focus: The focus of this study is to understand the climatic influence on precipitation isotopic composition and the mechanism underlying the seasonal isotope variation of precipitation in the Poyang Lake Wetland. New hydrological insights for the region: The Local Meteoric Water Line was established as δ2H = (8.83 ± 0.18) × δ18O + (12.77 ± 0.86) (R2 = 0.93, p < 0.01, n = 186). A total of seven moisture sub-sources contributing to precipitation were identified using the HYSPLIT model, among which distinct differences in isotopic signatures were revealed. The seasonal isotopic variation of precipitation in the study area was found not to respond to local meteorological factors. An increase in the relative occurrence frequency and relative contribution to precipitation of the continental source was found from summer to winter, which explains the seasonal variation in precipitation δ18O and d-excess. Combining the results of back trajectory analysis and isotopic statistics for the sub-source classification, the seasonal evolution of precipitation isotopes is considered to be caused by variations in the contribution from various moisture sources with distinct isotopic characteristics, which are further controlled by monsoon activities. This study highlights the importance of regional-scale moisture source dynamics and atmospheric circulation for the seasonal isotope variation of precipitation in the Poyang Lake Wetland.

Keywords

• Precipitation isotopes
• Moisture source identification
• Seasonal variation
• D-excess
• Poyang Lake Wetland