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

Abstract

The stable isotopes in precipitation (δD and δ 18 O) 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 (April-October) at alpine ecosystem, a representative site in the monsoon to non-monsoon transitional area of north-central China. The Local Meteoric Water Line was δD = (7.95 ± 0.16) δ 18 O + (15.79±1.77) (R 2 = 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‰). 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.

Hydrochemical and Isotopic Characteristics and the Spatiotemporal Differences of Surface Water and Groundwater in the Qaidam Basin, China

“…The differences in internal and external factors within the basin were analyzed spatially, examining the geological lithology and genesis relative to an understanding of the reasons for differences in water chemistry among the watersheds. Based on the ERA-5 reanalysis dataset and utilizing the Water Accounting Model (WAM)-2Layer water vapor flux statistical model [29], the analysis of deuterium excess (d-excess) [30] was combined to examine the water vapor sources for precipitation in the southern and northern basin watersheds, revealing spatial differences. The Gibbs model [31] was used to analyze the influence mechanisms of water chemistry in summer and winter seasons.…”