Characteristics and Moisture Sources of the Stable Isotopes in Precipitation at the Monsoon Marginal Region of North-Central China

摘要

The stable isotopes in precipitation (delta D and delta 18O) are important source signatures for understanding the hydrological cycle and paleoclimatic reconstruction, but little is known about these characteristics in monsoon marginal region of China. Here, 160 precipitation samples were collected in 2014 (AprilOctober) at alpine ecosystem, a representative site in the monsoon to non-monsoon transitional area of north-central China. The Local Meteoric Water Line was delta D = (7.95 +/- 0.16) delta 18O + (15.79 +/- 1.77) (R2 = 0.988), which had a similar slope but higher intercept than that of the Global Meteoric Water Line, indicating the precipitation in this area is mainly sourced from the ocean surface transported via monsoons. Additionally, the secondary evaporated water by continental recycled moisture was identified by the significantly higher d-excess value (16.09 parts per thousand). Backward trajectories by HYSPLIT model indicated seasonal moisture transport changes, which mainly from the Westerly winds in April, the Pacific Ocean in July, and the Indian Ocean in September. Positive temperature-isotopic signature effect was observed in the snow season (before mid-May); however, precipitation amount effect was observed in the monsoon season (June-August), and neither effect was significant in the whole year. These findings suggest the precipitation stable isotopes can be potentially utilized to reconstruct the precipitation signals in this region.