Preliminary research on hydrogen and oxygen stable isotope characteristics of different water bodies in the Qilian Mountains,northwestern Tibetan Plateau

Hydrogen and oxygen stable isotope in water bodies is a widely used tracer in hydrological process studies. In order to provide a basis for stable isotopic characteristics in different water bodies at the high mountainous area of northwestern Tibetan Plateau, samples for river water, groundwater, soil water, and plant water were collected from 10 sites in the Qilian Mountains during July and August 2015, and then analyzed for δ¹⁸O and δD, respectively. Results indicated that the stable isotope values of soil water were mostly plotted below the global meteoric water line (GMWL), which suggested that evaporation made heavy isotope in soil water enriched. The stable isotope values of soil water were quite different in the top soil layer, but tended to be uniform in the deep soil layer. Furthermore, the stable isotope difference of plant water is related to climatic conditions, water isotopes utilized by plant, plant species, growing season, and so on. Additionally, the variation of δ¹⁸O values for river water and groundwater relatively coincided with each other, and this showed the recharge sources of above two water bodies may be consistent. The stable isotope values of river water and groundwater were mainly plotted on the upper left of GMWL, and the lower level of isotopic fractionation due to weak evaporation may accountable for this.