哈尼梯田麻栗寨河流域泉水氢氧同位素的海拔效应

Altitude effect of hydrogen and oxygen isotopes in spring water of the Malizhai River basin,Hani terrace

氢氧同位素是示踪流域水循环过程的有效方法，水是维系哈尼梯田景观稳定性的关键．以哈尼梯田文化景观遗产核心区的麻栗寨河流域泉水为研究对象，通过采集不同海拔的33个样品分析泉水氢氧同位素的海拔效应．结果表明：总体上看，泉水氢氧同位素随海拔的上升而下降，其递减率随海拔增加而变大，并具有高、中、低三段海拔分异的特征；低海拔段（1060m以下）和高海拔段（1510m以上）均具有明显的海拔效应，但中海拔段（1060～1510m）相关关系不显著；泉水氢氧同位素关系方程与全国大气降水线相比斜率略小，说明在泉水形成之前曾受雨量效应、蒸发作用和补给等因素影响；在氘盈余方面，低海拔段的d值与全国大气降水线相当，中海拔段明显低于全国大气降水线，高海拔段明显高于全国大气降水线，说明研究区泉水存在强烈的混合作用，且其海拔效应是在补给水源多次循环和利用过程中形成．

Hydrogen and oxygen isotope can be used to trace hydrological cycle effectively. Water is the key element to maintain the stability of Hani Terrace landscape. In this paper, the spring water from the Malizhai River basin was taken as the research object. The basin is located at the core area of Hani Terrace, a World Cultural Heritage. From the basin, spring water samples were collected at different altitudes to analyze altitude effect of the hydrogen and oxygen isotopes. The results indicate： （ 1 ） Overall, spring water oxygen and hydrogen iso- tope decrease with altitude, with a lapse rate increasing with altitude, and characterized by three section elevation differentiation. （2） The low elevation section （less than 1 060 m a. s. 1. ）, and high elevation section （more than 1 510 m a. s. 1. ） have a significant altitude effect, but the middle-altitude section （ 1 060 - 1 510 m a. s. 1. ） has no significant altitude effect. （3） The relation equation of spring water＇s hydrogen and oxygen isotope has somewhat lower slope as compared with the national average, which indicates some impacts from rainfall, evaporation and replenishment to the spring water. （4） As regard to the deuterium excess, the deuterium excess value in low-altitude section is almost the same as the meteoric water line of China, while in the middle-altitude section, it is lower than the meteoric water line and in the high-altitude section, it is higher than the meteoric water line. To sum up, there is a strong mixing process within the spring water of the study area; the altitude effect of spring water＇s hydrogen and oxygen isotopes is due to the multiple water cycle as well as water use.