Li Yong-Ge, Li Zong-Xing, Feng Qi, Xiao Lian-Gui, Lü Yue-Min, Gui Juan, Yuan Rui-Feng, Zhang Bai-Juan
Key Laboratory of Ecohydrology of Inland River Basin/Gansu Hydrology and Water Resources Engineering Research Center, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Huan Jing Ke Xue. 2018 Jun 8;39(6):2661-2672. doi: 10.13227/j.hjkx.201708087.
Precipitation samples and meteorological data were collected simultaneously during individual precipitation events at Tuole station (3367 m a.s.l.) and Jiayuguan station (1658 m a.s.l.) in the Tuolai River Basin. A study of temporal variation, Local Meteoric Water Lines, and altitude change on precipitation stable isotopes was conducted. The relationships between precipitation stable isotopes and temperature, precipitation, average vapor pressure, and relative humidity were determined in order to explore the environmental significance of the stable isotopes at different altitudes in the middle reaches of the Qilian Mountains. The analysis indicated that the stable isotopes of the precipitation in Tuole and Jiayuguan station were characterized by pronounced seasonal variation, with Tuole having higher δO values in summer and autumn and lower δO values in spring and winter, while Jiayuguan displays higher δO values in spring and lower in other seasons. The -excess was correlated negatively with δO, and the correlation coefficients between δO and -excess decreased with increasing altitude due to weakening sub-cloud evaporation. The slope and intercept of the Local Meteoric Water Lines from Jiayuguan to Tuole rose significantly, showing an increasing trend from low altitude to high altitude. For the precipitation events above 10℃, δO of Tuole was positively correlated with the temperature, but the Jiayuguan results indicated the opposite. Sub-cloud evaporation weakened with high precipitation events in Jiayuguan. δO an-excess were positively correlated with the average vapor pressure, which declined from Tuole to Jiayuguan. Since the water vapor pressure and saturated water vapor pressure increased, it was difficult to form precipitation with decreasing altitude. The local strong sub-cloud evaporation caused δO and δD was positive at low altitude, while the effect of moisture recycling is obvious, such that δO and δD are negative in high altitude areas. There is no significant positive correlation between the δO and the relative humidity of the precipitation in Jiayuguan, while Tuole displays an opposite pattern. The results of the study will provide a scientific basis for further study of precipitation isotopes in the Tuolai River basin.
在托来河流域的托勒站（海拔3367米）和嘉峪关站（海拔1658米），在各个降水事件期间同时采集了降水样本和气象数据。开展了降水稳定同位素的时间变化、本地大气降水线及海拔变化研究。确定了降水稳定同位素与温度、降水量、平均水汽压和相对湿度之间的关系，以探讨祁连山中游不同海拔高度稳定同位素的环境意义。分析表明，托勒站和嘉峪关站降水的稳定同位素具有明显的季节变化特征，托勒站夏季和秋季的δO值较高，春季和冬季较低，而嘉峪关站春季的δO值较高，其他季节较低。过剩值与δO呈负相关，由于云下蒸发减弱，δO与过剩值之间的相关系数随海拔升高而降低。从嘉峪关到托勒的本地大气降水线的斜率和截距显著上升，呈现出从低海拔到高海拔的增加趋势。对于温度高于10℃的降水事件，托勒站的δO与温度呈正相关，但嘉峪关站的结果则相反。嘉峪关站高降水事件时云下蒸发减弱。δO和过剩值与平均水汽压呈正相关，平均水汽压从托勒站到嘉峪关站递减。由于水汽压和饱和水汽压增加，随着海拔降低难以形成降水。局部强烈的云下蒸发导致低海拔地区的δO和δD为正值，而水汽再循环的影响明显，使得高海拔地区的δO和δD为负值。嘉峪关站降水中δO与相对湿度之间没有显著的正相关关系，而托勒站则呈现相反的模式。该研究结果将为进一步研究托来河流域的降水同位素提供科学依据。
