Wanjun Zhang: Mountain Ecological Engineering and Ecohydrology

Stable Isotopic Characterization in Precipitation, Soil Water and Groundwater in Taihang Mountain, North China

Wanjun Zhang, Fadong Li, Jiansheng Cao, Xiuping Liu, Hehui Wang and Xiaohua Hao

Some previous studies showed that the transpiration by root uptake was a nonfractionation process and did not affect the isotopic composition of the soil water (Allison, et al., 1984; Dawson & Ehleringer, 1991). More detailed research with soil hydraulic properties and the isotope model should be carried out and would be helpful in assessing the evaporation accurately.

The stable isotopic compositions (18O, 2H) of water samples were used to investigate the characteristics of precipitation, soil water and groundwater in Taihang Mountain,north China. Soil water in the profiles at depths of 10, 20, 30, 50, 70, 90, and 110 cm were taken at two slopes covered by robinia and grass in an experimental catchment.

The slope and intercept of the local meteoric water line were both lower than the global meteoric water line (GMWL), with mean ？？18O of -8.11 ？？ 2.34？？. The effect of vegetation on the changes of ？？18O and ？？D is similar and weak for reducing the fractionation caused by evaporation effects. The large potential evaporation masks the vegetation cover effect. The non-evaporation plane is below 110 cm in this region. Local groundwater aquifer is recharged by several heavy rain events with light isotopic composition as explained by the piston model. The relationship between precipitation, soil water along vertical profiles, and groundwater is described conceptually associated with isotope profiles in two slopes. The results will provide valuable insights for further research on mountain hydrology using the stable isotope method.