作为水环境的重要指示剂,稳定同位素已经成为区域水文学、气候学研究的重要工具.降水作为水循环的输入项,其同位素组成是研究山地地表水过程、地下水形成转化、冰川变化等问题的必要信息.为了进一步增加对于青藏高原西北部降水过程及其控制因素的认识,本文基于青藏高原西北部五个长期观测站点降水中 δD和δ18 O数据,研究了青藏高原西北部与塔里木盆地交界地区大气降水稳定同位素时空分布特征.分析结果显示该地区降水稳定同位素季节变化较为明显,表现出夏高冬低的变化趋势,不同月份呈现出不同的空间分布特征.除狮泉河站降水δ18 O值与温度关系不显著外,其余站点δ18 O值随温度升高而增加.区域内降水量对降水δ18 O值的影响不显著,降水稳定同位素高程效应明显,降水δ18 O值随海拔上升而降低.降水过量氘(d值)的分布也呈现出显著的季节差异,总体表现出夏半年高、冬半年低的特点,受水汽再循环的影响,西合休站夏季降水的d值呈现较高的水平.研究表明,气温是控制该地区降水同位素分馏的重要因素,通过对于该区域降水蒸发比的计算发现,该地区临近沙漠的和田站的降水同位素受蒸发作用最为显著,而高海拔地区的狮泉河站降水受蒸发影响最小.%As an important indicator of water environment,stable isotope has become an important tool for regional hydrology and climatology research. Precipitation as an input of water cycle,its isotopic composition is necessary information for the study of mountain surface water process,groundwater formation and transformation,glacial change and other issues. In order to further increase understanding of the precipitation process and its controlling factors in the northwestern Tibetan Plateau,this paper has studied spatial and temporal distribution characteristics of stable isotope of atmospheric precipitation in the area between the northwestern Qinghai-Xizang Plateau and the Tarim Basin,based on the data of precipitation δD and δ18 O obtained at five long-term observation stations in the northwest of the Tibetan Plateau. The analysis results showed that the seasonal variations of precipitation stable isotopes in this area were obvious,showing a trend of high in summer and low in winter,and in different months it presented different spatial distribution characteristics. Except that the precipitation δ18 O value at the Shiquanhe station had no significant relationship with temperature,theδ18 O values at other stations increased with the increase of temperature. The influence of precipitation in the area on the value of precipitationδ18 O was not significant,but the elevation effect of precipitation stable isotope was obvious. The value of precipitation δ18 O decreased with elevation. The distribution of precipitation excess deuterium ( d value ) also showed a significant seasonal difference. The overall pattern was high in summer and low in winter. Affected by water vapor recirculation,the value of d in summer precipitation at Xihehei station was higher. Studies suggested that temperature was an important factor in controlling the isotope fractionation of precipitation in the area. Through the calculation of the precipitation-evaporation ratio in this area,it was found that the precipitation isotopes at the Hetian station near the desert were most significantly affected by evaporation,and at the Shiquan station with high altitudes,precipitation was minimally affected by evaporation.
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