青海湖流域降水和河水中δ^(18)O和δD变化特征

The Variation Characteristics of δ^(18)O and δD in Precipitation and River Water, Qinghai Lake Basin

稳定同位素方法已被广泛用来研究水循环过程中的水汽来源分析、不同水体间补给关系及水量平衡。论文基于青海湖流域2012年夏季所收集的河水和逐次大气降水中δ18O和δD及实测的气象数据,分析了它们的氢氧稳定同位素时空变化特征。结果表明:降水中同位素值组成变化存在两个明显的变化阶段,在8月中旬之前降水中稳定同位素值较低,而之后明显偏高,这与受夏季风和局地再循环水汽的影响有关;该流域大气降水线(LMWL)的斜率(8.69)和截距(17.5)明显大于全球大气降水线(GMWL),表明青海湖流域夏季大气降水在一定程度上受夏季风所携带湿润海洋性气团的影响;降水中稳定同位素与降水量及温度之间存在负相关关系,表明青海湖流域夏季降水中稳定同位素存在显著的降水量效应,但却不存在温度效应;该流域内河水受到大气降水、地下水及冰川融水的混合和调节作用,这使得河水中稳定同位素的波动范围比降水小;通过瑞利分馏模型模拟了降水中稳定同位素的变化,降水中δ18O、δD和过量氘(d_excess)的值受青海湖湖面再循环水汽补充的影响。因此,这也将为今后展开青海湖流域水循环过程中大气降水-地下水-地表水的研究提供科学依据,掌握该流域不同水体间的转化关系及水资源利用、管理具有重要的意义。

The technique of stable isotope has been widely applied to study the moisture source, supplement relationships among different water bodies and water balance in water cycle. Based on the δ18O and δD of event-based precipitation and river water, the meteorological data in the summer during 2012 on Qinghai Lake Basin, we analyzed the spatial and temporal variation characteristics of stable isotopes(oxygen and deuterium) in event-based precipitation and river water. The results indicated that the compositions of stable isotopes in precipitation presented two distinct variation phases, low isotopic values were showed before the mid August, but after that the isotopic values became higher, this may be related with the recycled local moisture and summer monsoon; the slope(8.69) and intercept(17.5) of LMWL(local meteoric water line) were evidently larger than GMWL in the Qinghai Lake Basin, this showed that the summer precipitation was partly influenced by the moist maritime air masses carried by summer monsoon; there was a negative correlation between stable isotopes in precipitation and precipitation amount and temperature, which indicated that a significant precipitation amount effect existed in summer precipitation but no temperature effect; the variation of stable isotopes in river water had a lower fluctuation range than that of precipitation, this was induced by the mixture and adjustment of precipitation, groundwater and glacier melt water; the compositions of stable isotopes in precipitation became larger replenished by the recycled moisture from Qinghai Lake in summer via Rayleigh fractionation model. Therefore, these would provide the scientific basis for the study of precipitation, groundwater and surface water in hydrologic cycle in Qinghai Lake Basin, and are of great significance for understanding the transforming relationships among different water bodies, utilization and management of water resources in future.