典型温冰川区湖泊的稳定同位素空间分布特征

Spatial Distribution of Stable Isotope from the Lakes in Typical Temperate Glacier Region

2014年8月对拉市海表层及不同深度湖水进行采样,分析拉市海湖水的氢氧稳定同位素的空间变化及其影响因素,探讨典型温冰川区域湖泊的水文补给特征.结果表明,拉市海表层湖水的δ^(18)O、δD值分别在-12.98‰~8.16‰和-99.42‰^-73.78‰之间波动,平均值分别为-9.75‰和-82.23‰;表层湖水的δ^(18)O及过量氘表现出相反的空间变化特征,有河水注入的区域δ^(18)O值较低而过量氘值较高;垂直方向上过量氘随深度变化较小,表明湖水在垂直方向上混合较充分,不同深度层上过量氘表现出自东向西先增大后减小的变化趋势,这可能与入湖河流的分布、湖泊所处的地理位置及自然条件等密切相关;同位素对比研究发现,拉市海的主要补给源为大气降水及河水,冰雪融水可能间接补给拉市海;对拉市海与青藏高原地区典型湖泊和非冰川区湖泊的氧同位素组成对比发现,冰川区湖泊中稳定同位素表现出明显的高程效应(拉市海除外),δ^(18)O随海拔升高而降低.非冰川区湖泊蒸发效应较为明显,同位素值明显偏正.

We focused mainly on the spatial variation and influencing factors of hydrogen and oxygen stable isotopes between water samples collected at the surface and different depths in the Lashi Lake in August,2014. Hydrological supply characteristics of the lake in typical temperate glacier region were discussed. The results showed that the values of δ^（18）O and δD in the Lashi Lake ranged from- 12. 98‰ to- 8. 16‰ with the mean of- 9. 75‰ and from- 99. 42‰ to- 73. 78‰ with the mean of- 82. 23‰,respectively.There was a reversed spatial variation between δ^（18）O and d. Relatively low values of δ^（18）O with high values of d were found at the edge of the lake where the rivers drained into. Meanwhile,the values of d in the vertical profile varied little with depth,suggesting that the waters mixed sufficiently in the vertical direction. The d values increased at first and then decreased from east to west at different layers,but both increase and decrease exhibited different velocities,which were related to the river distribution,the locality of the lake and environmental conditions etc. River water and atmospheric precipitation were the main recharge sources of the Lashi Lake,and the melt-water of snow and ice might also be the supply resource. The δ^18O values of lake water in glacier region decreased along the elevation（ except for Lashi Lake）,generally,this phenomenon was called ＂ altitude effect＂. Moreover,high isotopic values of the lake water from non-glacier region were due to the evaporation effect.