羊卓雍错流域湖水氧稳定同位素空间分布特征

The Spacial Distribution of Oxygen Stable Isotope in the Yamzho Lake Basin,Xizang(Tibet)

2006年8月17日至9月1日对羊卓雍错和普莫雍错表层湖水以及深层湖水进行采样,共采集到55个表层水样和39个深水样,通过测量水样氧稳定同位素比率,初步揭示了该流域湖水水体中δ18O的空间变化.结果表明:羊卓雍错和普莫雍错湖水的δ18O值随深度增加逐渐增大,其主要受冰川融水补给的影响.羊卓雍错表层湖水的δ18O值变化较大,主要是和羊卓雍错湖水动力混合不充分有关,一般河水汇入区δ18O值都表现为较低值.普莫雍错表层湖水的δ18O值变化较小,由冰川融水主要补给的西岸、南岸至湖心,δ18O值逐渐增大,说明冰川融水汇入湖泊后的混合靠扩散过程和蒸发过程的作用.湖水中δ18O值高于当地冰川融水,表明湖水蒸发强烈.同时,通过均值分析,还发现羊卓雍错和普莫雍错表层湖水δ18O值存在显著差异.

Stable isotope approaches are often used for estimating water balance of lakes. In this paper, an oxygen stable isotope database is presented for estimating spatial variations of δ^18O in lakes. Lake （or river） water samples were collected in Yamzho Lake and Puma Lake between 17 August and 1 September, 2006. These samples were analyzed in the laboratory for oxygen isotope component. The analysis results show that the δ^18O values of the surface water in the two lakes are fairly constant. Because of the strong evaporation on the lake surface, the δ^18O values of lake water is much higher than δ^18O values in precipitation and river water, which is mainly derived from the glacier meltwater. The δ^18O of lake water in the Yamzho Lake increases with depth, and the water temperature did not affect the δ^18O in the lake apparently. The δ^18O of lake water increases with the depth in the Puma Lake, which is possibly due to morphologies and meltwater inflow. According to independent-samples T-test, the δ^18O values of the surface water in the two lakes can be distinguished.