Spatial variations of δD and δ18O in lake water of western China and their controlling factors

湖泊水体的氢氧同位素（δD、δ18O）是研究区域大气降水和水文循环的重要手段之一，目前对其的研究主要以单一湖泊为主.以2016年夏季在中国西部地区采集的33个湖泊水体为研究对象，分析其氢氧同位素的变化特征，并结合当地夏季大气降水、湖水盐度、海拔与纬度等资料，探讨中国西部33个湖泊水体δD、δ18O的空间分布特征及其影响因素.结果表明：33个湖泊水体的δD与δ18O组成主要受控于大气降水，但受蒸发分馏的影响，湖水线的斜率与截距低于大气水线.湖泊水体与夏季大气降水氢氧同位素存在明显的空间分异，这种分异与湖水盐度无关，主要受到区域降水水汽来源不同的影响.青藏高原南北两侧由于水汽来源及蒸发条件的不同，使得青藏高原湖泊水体的氢氧同位素呈现出“北高南低”的特点，新疆西北部受西风影响，湖泊水体的氢氧同位素明显偏负，内蒙古及邻近地区受东南季风的影响，湖水受到蒸发分馏作用使其δD与δ18O偏正.不同区域湖泊水体的氘盈余（d_excess）反映了不同的水汽源地的湿度状况而不能指示湖水的蒸发状况.受降水影响，青藏高原地区湖水氢氧同位素组成与海拔高度呈负相关，与纬度呈正相关.;The compositions of hydrogen and oxygen stable isotopes (δD and δ18O) in lake water are important proxies to study regional precipitation and hydrological cycle. At present, the research on hydrogen and oxygen stable isotopes of lake water mainly focused on a single lake. In this study, combined with hydrogen and oxygen stable isotopes in local summer precipitation, the lake salinity, the elevation and latitude of the lakes, 33 lake water samples collected in western China in the summer of 2016 were used to investigate the spatial variations of δD and δ18O in water of 33 lakes and their controlling factors. The results showed that the compositions of δD and δ18O in lake water dominated by precipitation. Due to the influence of evaporation on isotopic fractionation, the stable isotope slope and intercept of Lake Water Line in western China are below these of the Global Meteoric Water Line. Spatial distribution of the hydrogen and oxygen isotopes in 33 lake waters varies in different regions, which is mainly controlled by the hydrogen and oxygen isotope components of meteoric waters in different regions rather than lake salinity. The hydrogen and oxygen isotopes of lake waters in the Tibetan Plateau are characterized by “high north and low south”, which is caused by different water vapor sources and evaporation between the north and south of the Tibetan Plateau. In northwestern Xinjiang affected by westerlies, the hydrogen and oxygen stable isotopes are negative, while the lake water isotopes in Inner Mongolia and adjacent areas controlled by East Asia monsoon are positive subjected to evaporation fractionation. The d_excess of lake waters in different regions may reflect diverse water vapor source rather than the evaporation effects of lake water. Influenced by the precipitation, the compositions of hydrogen and oxygen isotopes in the lakes of the Tibetan Plateau are negatively correlated with altitude and positively correlated with latitude.