Research advances in water vapor isotopic composition and its application in the hydrological research

Stable isotope technique provides a great deal of valuable information for the research of the hydrologic cycle, which could also be extensively used in hydrology, aerology, ecology and other related fields. Recent development in absorption spectroscopy technology has made it possible to make in situ, continuous observations of the 18O and D of atmospheric water vapor. In this review, the study of water vapor isotope composition were described in detail from 5 aspects. Firstly, we summarized the calibration methods for in situ 18O and D measurements made by commercial water vapor isotope analyzers. Secondly, the pattern of water vapor isotope composition were explored. Thirdly, the pattern of deuterium-excess（d） was discussed. Fourthly, through surveying a considerable amount of the documents, we found that the plant transpiration dominated local evapotranspiration both in the forest and in the agricultural ecosystems in arid and semi-arid region. Fifthly, the 3 models of estimation of leaf water 18O enrichment were briefly introduced. As the measurement sites of water vapor isotopic composition are scarce, the establishment of the network and long-term observation will greatly benefit the research of ecological hydrologic cycle. Meanwhile, combining the measurement of water vapor isotopic composition with the observation of fluxes and remote sensing models, will further reveal the pattern and mechanism of water cycle at regional and global scale.［Ch, 1 tab. 81 ref.］