天山乌鲁木齐河流域山区降水δ18O和δD 特征及水汽来源分析

依据乌鲁木齐河流域山区3个站点实测次降水δ18O和δD数据以及气象观测资料,结合临近GNIP(Global Network of Isotopes in Precipitation)站点数据,对其降水δ18O和δD特征及水汽来源进行了分析。结果表明,大气降水中δ18O值波动范围大,但呈现明显的季节性变化:冬季降水δ18O较低,夏季降水δ18O较高。受流域山区气候和地理条件影响,从上游到下游各站点大气降水线截距和斜率均呈现逐渐减小趋势。大气降水中δ18O和δD与日均气温存在密切正相关关系,且温度与δ18O之间的相关性优于δD。降水中d-excess值也表现出季节性变化,冬季降水d-excess值高于夏季降水。利用HYSPLIT 4.0气团轨迹模型,得出夏季水汽主要来源西风环流输送,冬季受西风环流和极地气团共同影响。

Characteristics of δ18O and δD in precipitation and its water vapor sources in the upper Urumqi River basin,Eastern Tianshan

The stable isotopes characteritics of hydrogen and oxygen in precipitation is an important aspect of the regional isotope hydrologic cycle. The variations of δD and δ¹⁸O values in event-based precipitation samples are analyzed. The samples were collected from three stations (No.1, Zongkong, Houxia) in the upper Urumqi River basin from May 2006 to August 2007. The δ¹⁸O in event-based precipitation exhibits an extremely wide range and a distinct seasonal variation with enriched values in summer and depleted values in winter. The slopes and intercepts of the local meteoric water lines (LMWLs) along the Urumqi River Basin are No.1>Zongkong>Houxia>Urumqi the nearest Global Network of Isotopes in Precipitation (GNIP) station. The δ¹⁸O and δD values in event-based precipitation and the mean air temperature show a significant positive correlation, and a better linear relation exists between δ¹⁸O and air temperature than that of δD. Seasonal variations can be observed in d-excess of precipitation. The results of air-mass back trajectories of each precipitation event with the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model indicate a dominant effect of westerly air masses in summer and the integrated influence of westerly and polar air masses in winter for the study area.