氢、氧稳定同位素方法是研究多年冻土区水文过程的一种有效手段。基于2009年风火山流域降水和河水δD和δ18O数据,结合水文气象资料,分析多年冻土区季节性河流氢、氧同位素组成。研究表明,研究期间(6—10月)δ18O、δD和氘过剩河水与降水均呈下降的趋势,表明研究区降水是河水的重要补给来源。2#、3#流域δD分别为-66.8‰和-69.6‰,与降水δD(-66.7‰)基本相当;5#流域δD为-62.4‰,显著高于降水。5#流域较高的植被覆盖使地表具有更高的有机质含量、水分和蒸散量,其强烈的蒸发分馏作用使河水富集重同位素。6月份,随着土壤向下融化,降水(δD=-12.1‰)驱替冻结封存的重同位素贫化的土壤水(δD=-71.3‰)补给河流;10月份,地表冻结后抑制降水下渗,使降水和河水δD趋于一致,反映了土壤冻融过程在多年冻土区径流过程中起到的重要影响。该研究为多年冻土区水文过程的变化规律提供了同位素证据。 更多还原
 

Frozen soil plays a key role in hydrological processes and their observations are rare and difficult in permafrost regions. The stable hydrogen and oxygen isotope methods provide a useful tool for permafrost hydrology research. In this study, stable hydrogen and oxygen isotopes composition in seasonal river water was analyzed based on the stable isotope ratios (8D and delta~(18)O) data in precipitation and river water in a permafrost watershed in Yangtze River headwater region in 2009, combined with meteorological and hydrological data. The results showed that the delta~(18)O, 8D and the excess deuterium variation of river water and rainfall all presented descending trends during research period. This implies that the precipitation is the most important source of river water. The 8D in river water in the 2nd and 3rd sub-basin were -66.8%o and -69.6%o, respectively ,which were similar to the 8D in precipitation (-66.7%o). However, the 8D in river water in the 5th sub-basin (62.4%o) was significantly higher than that in precipitation. Higher vegetation coverage in the 5th sub-basin,higher soil organic matter content,soil moisture and actual evapotranspiration and strong evaporation fractionation effect enriched river water in the 5 th sub-basin with heavy isotopes. In June,as the soil melt down,frozen soil water of heavy isotope (8D, -71.3%。) was displaced by precipitation (deltaD, -12.1%o) and then fed the river water. In October, the frozen soil inhibited precipitation infiltration and made hydrogen isotope change quickly with precipitation. These indicate that the freeze-thaw cycle plays an important role in runoff processes in the permafrost regions. This study provides isotopic evidence in hydrological cycle research and a theoretical support of water resource protection in permafrost regions.