干旱区生态环境知识资源中心

A study of spatial and temporal variability of precipitation isotope composition on the southern and north slopes of Wushaoling Mountain was conducted in order to explore the processes influencing its evolution. The analysis indicated that the isotopic composition, the slopes and intercepts of Local Meteroic Water Lines, altitude gradients and temperature effect are higher on the north slope than those on the south slope. The d-excess showed an increase from lower to higher altitudes, and the altitude gradients changed with season. The correlation coefficients between delta O-18 and d-excess decreased with increasing altitude due to weakening sub-cloud evaporation. Westerly wind principally dominates Wushaoling Mountain, so the relatively negative stable isotope values observed are related to the long distance transportation of water vapor in spring and winter. In summer and autumn, the locally strong sub-cloud evaporation cause relatively higher delta O-18 and lower d-excess. The results suggested that the sub-cloud evaporation has enriched the delta O-18 composition by 23%, 23%, 32%, 42% and 29% in May, June, July, August and September, respectively. In some circumstances, delta O-18 and 80 were depleted at the end of multi-days rainfall events due to the rainout process. In addition, monsoonal moisture caused some negative delta O-18 in summer when an enhanced cyclonic circulation had developed on Tibetan Plateau. The study enhances the knowledge of isotopic evolution of precipitation and provides a basis for further study of isotopic hydrology in arid regions. (C) 2016 Elsevier B.V. All rights reserved.