Characteristics and moisture sources of the stable isotopes in
precipitation in the monsoon marginal region of north-central China
Abstract
The stable hydrogen and oxygen isotopes in precipitation (δD and δ18O,
respectively) are important source signatures for understanding the
hydrological cycle and paleoclimatic reconstruction. In this study, 32
precipitation samples were collected from April to October 2014 at the
Luya Mountain summit, a representative site in the monsoon marginal area
of north-central China. The isotopic signatures of precipitation
exhibited strong seasonal variations ranging from -185.61‰ to -18.50‰
and -25.51‰ to -4.59‰ for δD and δ18O, respectively, which were
relatively higher in August and lower in September. The local meteoric
water line was δD=(7.95±0.16) δ18O+(15.79±1.77) (R2 = 0.988, N = 32, p
< 0.001), which had a similar slope but higher intercept than
that of the global meteoric water line, indicating that 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 deuterium excess value (16.09‰). Backward trajectories generated
via the Hybrid Single-Particle Lagrangian Integrated Trajectory model
indicated seasonal moisture transport changes in the studied monsoonal
marginal region, in which the main moisture sources were the Westerly
winds in April, the Pacific Ocean in July, and the Indian Ocean in
September. Secondary evaporated water from the alpine ecosystem may also
influence the local atmospheric water cycle throughout the year.
Positive temperature-isotopic signature effect (δD and δ18O) was
observed in the cold season (before mid-May); however, the precipitation
amount effect was observed in the monsoon season from June to August,
and both effects became vague across the entire period. These findings
suggest that the stable isotope compositions of precipitation can be
utilized to determine the moisture sources in the monsoon marginal
region of north-central China and potentially be utilized to reconstruct
the precipitation signals in this region.