达里诺尔湖水体稳定氢、氧同位素组成变化对结冰过程的响应

利用自然界中广泛分布的环境同位素进行湖泊水体演化过程分析已经成为现代湖泊科学的重要研究方向.通过采集内蒙古达里诺尔湖(简称"达里湖") 2013年1月份的湖冰、湖水, 2012年夏季湖水与湖区大气降水等, 共分析了77个样品中稳定氢(H)、氧(O)同位素值的变化情况, 在此基础上对达里湖水体稳定H、O同位素组成变化及其对结冰过程的响应进行了详细分析, 结果显示: (1)伴随结冰过程的完成, 各站点深层冰体(厚度~65 cm)中δD、δ18O值比表层冰体(厚度~15 cm)中的值出现不同幅度的偏重.而冰下水体中δD、δ18O平均值则比冰体中的平均值分别偏轻约13.85‰、2.23‰.在冰层形成的快速与稳定阶段, δD、δ18O值的变化幅度也存在差异.同时, 冬季外源水体的输入对各站点间同位素值差异的影响比夏季更明显; (2)夏季湖水、冬季湖水与湖冰的同位素值均落在全球大气降水线与湖区大气降水线之外, 显示湖泊冰封之前, 蒸发对湖泊水体同位素偏移存在一定程度的影响; 而冬季湖水与湖冰的同位素值基本位于同一斜率区间, 且全部落在夏季湖水同位素值的右侧, 显示两者之间并不存在明显的蒸发分馏作用, 造成上述现象的因素只能归结于结冰过程. 

Changes of Stable Oxygen and Hydrogen Isotopes and Their Responses to Freezing Process in Dali-Nor Lake in Cold-Arid Areas of China

Utilizing the environmental isotopes, which exist widely as one proxy of lake water evolution process, has become one important direction in lake sciences.In this paper, a total of 77 samples of lake water, ice and precipitation water were collected in Dali-Nor Lake, which locates in cold-arid areas of Inner Mongolia; and changes of δD and δ18O and their responses to freezing process in Dali-Nor Lake are analyzed. The comparison of the changes of δD and δ18O among lake ice, lake water and precipitate water shows that: (1) Following the freezing process, the values of ΔδD, Δδ18O between bottom (65 cm) and surface (15 cm) ice layers are both above zero.But in fast stage and stable stage during lake ice forming, the change range of water stable isotopes is different.Meanwhile, the values of δD and δ18O in water under the ice are about 13.85 ‰ and 2.23 ‰ lighter than those in lake ice.In addition, the river inflows have more obvious influence on value changes of δD and δ18O among different sites in winter than in summer. (2) The δD and δ18O values of water (both summer and winter) and ice are both in right side of the global meteoric water line (GMWL) and local meteoric water line (LMWL), which shows that the evaporation process has certain influence on the fractional distillation of water stable isotopes before the lake ice formed. On the other hand, the values of δD and δ18O in lake ice and winter lake water have the same slope range and both in right side of the values of δD and δ18O in summer lake water, which shows that the freezing process has obvious influence on the fractional distillation of water stable isotopes during the lake ice forming process.