北麓河多年冻土区降水及河水稳定同位素特征分析

Characteristic analysis of stable isotope variation in precipitation and rivers in Beilu River permafrost region

为了进一步全面理解和探索青藏高原水文水循环过程，采用同位素方法并结合气象资料对青臧高原北麓河区域2011年6-12月降水和河水稳定同位素时空特征进行分析。探讨了北麓河降水同位素与日平均气温、降水量之间的相互关系，同时也对比分析了北麓河降水和河水的同位素变化特征。结果表明：北麓河降水同位素在整个观测期内总体受温度控制，但存存季节变化，其中6-9月降水同位素受到温度和降水量效应的共同控制，9月以后则主要受温度和降水量效应的共同控制，9月以后则主要受温度的影响。

As an indispensable part of the Qinghai-Tibet Plateau （QTP） water cycle, precipitation and surface water in QTP plays an important role in exploring the permafrost hydrological process and in studying the history of perma- frost development. Although enormous achievements in studying QTP precipitation and surface water have been made using isotopic methods, there has been a lack of relevant research on the subject in the Beilu River region of central QTP. In order to have a comprehensive understanding of the QTP water cycle and permafrost hydrological process, a study is conducted on the spatial-temporal characteristic of stable isotope variation in precipitation and rivers in the QTP Beilu River permafrost region. The isotopic composition and meteorological data from the region for the June-De- cember period of 2011 are used to analyze the relationships among stable isotopes, daily average temperatures, precip- itation amounts and flow water. Results show that temperature has a dominant effect on the stable isotopes in precipita- tion in the QTP Beilu River permafrost region. The isotopic seasonality of precipitation exists due to influences of both westerly and monsoon on local precipitation from June through December, which suggests that the stable isotopes in precipitation are controlled by both temperature and precipitation amounts. The stable isotope variation in rivers exhib- its a similar behavior to that in precipitation, suggesting that rivers are recharged by the precipitation fallen in the QTP Beilu River permafrost region. The influence of precipitation on stable isotope variation in rivers is determined by pre- cipitation amounts, i. e. , the smaller the precipitation amounts are, the lighter the influences become. When com- pared to the local meteoric water line of the QTP Beilu River permafrost region, both slope and intercept of the δ18O- δD relationships are larger for rivers, suggesting that rivers are also recharged by other sources within the regional wa- ter cycle and influenced by evaporative fractionation.