Seasonal variation in stable isotopic composition of alas lake water near Yakutsk, Eastern Siberia
Seasonal variation in stable isotopic composition of alas lake water near Yakutsk, Eastern Siberia
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DOI：
10.2343/geochemj.37.519
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发表时间：
2003-01-01
影响因子：
0.8
通讯作者：
Ohata, T
中科院分区：
文献类型：
--
作者：
Ichiyanagi, K;Sugimoto, A;Ohata, T
在西伯利亚东部雅库茨克附近的永久冻土区，对降水和湖水的稳定同位素组成的时间变化进行了详细的测量。2000年4月至8月，降水δ (18)O值约为-30 ~ - 5ppm，湖水δ (18)O值约为-25 ~ - 5ppm。12个站点周降水δ (18)O的变化趋势一致。湖泊δ (18)O的时间变化可分为同位素稳定型湖泊和非稳定型湖泊，前者变化量小于5ppm，后者变化量大于10ppm。在非稳态湖泊中，水来源于融雪，湖水的δ (18)O在夏季由于蒸发而逐渐富集。在稳定状态的湖泊中，水主要来自前一个夏天蒸发的富含o -18的湖水。同位素质量平衡模型利用瑞利分馏在每日时间步长上准确地描述了阿拉斯湖的时间体积和同位素变化。根据观测到的湖泊水量与模拟湖泊水量的差异，估计5月至8月土壤水（地下流量）的流入是恒定的（200 m(3)/天）。考虑同位素质量平衡，推断活动层下部的土壤水是流入的主要组成部分，其δ (18)O约为- 23ppm。
Detailed measurements of temporal variations in the stable isotopic composition of precipitation and lake water were conducted in the permafrost region near Yakutsk, eastern Siberia. The delta(18)O ranged from approximately -30 to -5parts per thousand in precipitation and from -25 to -5parts per thousand in lake water were observed from April to August, 2000. Temporal changes in delta(18)O of precipitation observed weekly at 12 sites all showed the same trend. The temporal variation of delta(18)O in lakes classified into two groups: isotopically steady-state lakes with less than 5parts per thousand variation, and non-steady-state lakes with variation exceeding 10parts per thousand. In non-steady-state lakes, the water originated from snowmelt, and the delta(18)O of lake water gradually enriched as a result of evaporation during the summer. In steady-state lakes, the water originated predominantly from O-18-enriched lake water that had evaporated in the previous summer. The temporal volumetric and isotopic variations in alas lakes are accurately depicted by an isotope mass-balance model using Rayleigh fractionation over daily time steps. The inflow of soil water (subsurface flow) was estimated to be constant (200 m(3)/day) from May to August, based on the difference between observed and simulated lake volumes. Taking the isotopic mass-balance into consideration, the soil water in lower part of the active layer is inferred as a major component of inflow which has a delta(18)O of about -23parts per thousand.