准噶尔盆地东南部降水中δ^(18)O的温度与降水量效应

Effect of Temperature and Precipitation on δ^(18)O in Precipitation Water in the Southeastern Junggar Basin,China

地区大气降水线(LMWL)和降水中δ^(18)O的温度和降水量级效应是应用稳定同位素技术研究地区水文学过程与问题的基础。通过跟踪2012—2013年准噶尔盆地东南部44次降水事件,测定了降水中的δ^(18)O和δD,同时收集降水过程的气温变化和降水量数据,在降水事件尺度上研究了降水中δ^(18)O、温度和降水量三者之间的关系。降水中的稳定同位素δ^(18)O和δD存在时间尺度效应,在不同的时间尺度上温度、降水量级效应与LMWL可能不同。在降水事件尺度上,准噶尔盆地东南部LMWL是δD=(7.53±0.22)·δ^(18)O+(0.25±3.29)。一年中受到水热同期变化的影响,降水量效应被强烈的气温季节动态所掩盖,因此,表面看来,处于欧亚大陆腹地的准噶尔盆地东南部只存在显著的温度效应,而不存在降水量效应,但是扣除气温的影响后,显著的降水量级效应仍然存在,降水量效应主要与云下二次蒸发有关。二元线性模型拟合结果表明:在降水事件尺度上,温度和降水量级效应分别为(0.70±0.03)‰·℃^(-1)和(-0.14±0.07)‰·mm^(-1)。

Local meteoric water line（ LMWL） and the temperature and precipitation amount of δ（18）O in precipitation water are the foundation in studying the local hydrological processes using hydrogen and oxygen stable isotopic technique. In this study,the values of δ（18）O and δD in precipitation water of 44 precipitation events were measured,and the data of air temperature and precipitation were collected by an automatic meteorological station in the southeastern Junggar Basin,China during the period of 2012- 2013. At the precipitation event scale,the relationships among the δ（18）O in precipitation water,air temperature and precipitation were studied. Because there was a temporal scale effect between δ（18）O in precipitation water and δD,the temperature and precipitation amount effect at different time scales may different from that at the precipitation event scale. At the precipitation event scale,the LMWL wasδD =（ 7. 53 ± 0. 22） ·δ（18）O ＋（ 0. 25 ± 3. 29）. Ostensibly,because of the heat and water concurrence in any one year,there was no precipitation amount effect but a significant temperature effect on δ（18）O in precipitation water. However,after removing the influence of temperature,there was also a significant amount effect on δ（18）O in precipitation water in the hinterland of Eurasia. It was inferred that the significant amount effect was associated with the secondary evaporation process of raindrop below cloud before falling on the ground. The temperature and precipitation amount effect were（ 0. 70 ± 0. 03） ‰·℃（-1）and（- 0. 14 ± 0. 07） ‰·mm（-1）,respectively thorough the binary linear regression model at the precipitation event scale.