大渡河丰水期水体氢氧同位素特征及其影响因素

Variations of hydrogen and oxygen isotopes in waterbody of Dadu River during flood period and their influencing factors

大渡河干流规划了29座梯级水电站,已建成13座。为了解环境和水电开发对大渡河河水氢氧同位素组成的影响,应用数理统计等方法对2020年9月采集的大渡河流域河水氢氧同位素和相关水文资料进行分析。结果表明:①大渡河水体δD和δ^(18) O的分布范围分别为-120.60‰~-77.98‰和-16.67‰~-11.90‰,河水的δD与δ^(18) O关系线为δD=8.01δ^(18) O+14.43(R^(2)=0.97,ρ<0.01);②氘盈余的范围为11.72‰~18.15‰,河水氘盈余值全部偏正,体现了大渡河水接受冰雪融水补给的特征;③δD和δ^(18) O沿程增加,表明从上游至下游重同位素逐渐富集,反映了该区域氢氧同位素分布具有海拔效应;④水电站的大坝拦截会对水体氢氧同位素含量产生一定影响,水库水体滞留时间较长会使得坝前水体重同位素富集。

There are 29 cascade hydropower stations planned in the main stream of Dadu River,and 13 have been constructed.In order to understand the influence of environment and hydropower development on the stable isotope composition of river water in the Dadu River,mathematical statistic was applied to analyze theδ^(18) O andδD of river water and related hydrological data collected in Dadu River in September 2020.The results indicated that:①the range ofδD andδ^(18)O were-120.60‰~-77.98‰and-16.67‰~-11.90‰respectively.The relationship betweenδD andδ^(18) O of river water wasδD=8.01δ^(18) O+14.3(R^(2)=0.97,ρ<0.01).②The d-excess values varied from 11.72‰to 18.15‰,and all of the values were positive,indicating the Dadu River was recharged by melting water of ice and snow.③δD andδ^(18) O increased along the river,suggesting that heavy isotopes were gradually enriched from upstream to downstream,which was likely to result from the“altitude effect”of hydrogen and oxygen isotopes in this area.④Dam interception had an impact on the hydrogen and oxygen isotope composition of the river water.The long residence time of water in the reservoir will lead to the enrichment of water isotopes before the dam.