湘江流域岳麓山周边地区不同水体中氢氧稳定同位素特征及相互关系

不同水体中稳定同位素的差异性组成对认识区域水文过程,如水体的补给机制、不同水体间的相互作用具有重要意义。论文基于2010—2013年湘江流域岳麓山周边地区降水、地表水、浅层土壤水和地下水中δD和δ¹⁸O的逐日数据及相关气象资料,分析了不同水体中稳定同位素的组成,揭示了不同水稳定同位素间的相互作用关系。结果表明：地表水、浅层土壤水和地下水中δD和δ¹⁸O对日降水中δD和δ¹⁸O的响应存在时滞,地表水和浅层土壤水的滞后时间较短,地下水的滞后时间较长;在天气尺度下,降水中δD和δ¹⁸O存在很好的线性关系,二者的相关系数达0.98;地表水、浅层土壤水和地下水中δD和δ¹⁸O的线性相关系数分别为0.95、0.90和0.90,均超过0.001的信度;在δD-δ¹⁸O关系中,地表水水线（SWL）、浅层土壤水水线（SSWL）和地下水水线（GWL）的斜率及截距都小于长沙大气水线（LMWL）,表明降水是区域地表水、浅层土壤水和地下水的主要补给水源,且在补给过程中,存在一定程度的蒸发,同时与其他水体存在混合交换作用;在季节尺度下,同一水体的水线斜率与截距具有正比关系,即斜率越大,截距越大;但LMWL斜率和截距的关系存在季节和年际的差异;对比同一类水线旱雨季的斜率,仅有LMWL的斜率旱季小于雨季,反映出旱季干燥的大气条件下,降落雨滴云下二次蒸发强烈的特点。

Characteristics of the Stable Isotopes in Different Water Bodies and Their Relationships in Surrounding Areas of Yuelu Mountain in the Xiangjiang River Basin

The stable isotopes in different water bodies are of great significance to the study of hydrological processes, such as recharge mechanism and the interaction among different waters. In order to characterize the isotopic composition and reveal the interrelationships among the stable isotopes in different water bodies in Changsha, the precipitation, surface water, shallow soil water and groundwater samples were collected in surrounding areas of Yuelu Mountain from 2010 to 2013. Meanwhile, auxiliary variables (time and amount of air temperature and precipitation) were also measured. These measurements indicated significant time lag effect of the responses of δD and δ¹⁸O in the surface water, shallow soil water and groundwater to those of the daily precipitation showed. The lag time of surface water and shallow soil water to the precipitation is shorter, but the groundwater is longer. There was a remarkable linear relationship between δD and δ¹⁸O of precipitation at the synoptic scale, with a correlation coefficient 0.98; and the correlation coefficients between δD and δ¹⁸O in the surface water, shallow soil water and groundwater is 0.95, 0.90 and 0.90 respectively. In the δD-δ¹⁸O relation pattern, the slopes and the intercepts of the Surface Water Line (SWL), Shallow Soil Water Line (SSWL) and Groundwater Water Line (GWL) are smaller than those of the Local Meteoric Water Line (LMWL), suggesting that the precipitation is the primarily sources of other water bodies, and it has experienced considerable degree of evaporation and mixed with other water bodies. At the seasonal scale, notable positive correlations between the slope and the intercept of the same water-line were observed, however we also found the correlations between the slope and the intercept of LMWL failed to obey the pattern. The slope of LMWL during the dry season is smaller than in the rainy season, which revealed that the raindrops had undergone strong secondary evaporation during their descending from the cloud.