基于同位素揭示艾比湖流域地下水特征

Characteristics of groundwater in Ebinur Lake Basin using isotopes method

地下水对于调节干旱区水循环和生态系统具有重要意义,认识和管理地下水资源是防止河流基流减少,地面沉降和水质退化的关键。通过分析艾比湖流域地下水水化学参数和氢氧稳定同位素特征,结合线性回归、双端元混合模型和GIS空间分析等方法,探讨不同区域地下水补给来源和水化学组分动态变化。结果表明:(1)博尔塔拉河(简称博河)和精河中下游区域氢氧同位素(δ2H与δ18O)值最大,艾比湖周边区域次之,博河上游区域最小,流域地下水存在不同的循环过程。(2)地下水氘盈余(d-excess)和水化学特征反映了地下水不同的补给机制和影响因素,博河上游区域地下水主要受冰川积雪融水补给;博河和精河中下游地下水主要来源为地表水和降水,同时受岩层性质、农田开发和灌溉措施影响较大;艾比湖周边地下水主要来源于冰雪融水和降水。中下游区域和河湖交汇区地下水是防控和治理的重点区域。(3)地下水流动系统Ⅰ的电导率(Electrical conductance,EC)在210.00~2500.00μS·cm^(-1)之间,d-excess在6.47‰~9.70‰之间;流动系统ⅡEC在141.60~5260.00μS·cm^(-1)之间,d-excess在9.61‰~17.45‰之间,地下含水层存在不同的水力联系。研究结果对艾比湖流域地下水氢氧同位素和水化学驱动机制的探讨,可以为流域地下水资源的合理利用及科学开发提供一定的理论参考依据。

Groundwater is important for regulating the water cycle and ecosystem in arid areas.Understanding and managing groundwater resources is the key to preventing the reduction of river baseflow,ground subsidence and water quality degradation.Therefore,this study analyzed the groundwater chemical parameters and hydrogenoxygen stable isotope characteristics of the Ebinur Lake Basin,Xinjiang,China,and explored the sources of groundwater recharge,dynamic changes of water chemical components in different regions by combining linear regression,two-terminal mixed model and GIS spatial analysis.The results showed that:(1)Different circulation processes of groundwater existed in different areas of the Ebinur Lake Basin,with the largest of hydrogen and oxygen isotopes(δ~2H andδ18O)in the middle and lower reaches of the Bortala and Jing Rivers,followed by the area around Lake Ebinur Basin,and the smallest in the upper Bortala River area.(2)Deuterium excess parameter(d-excess)parameter and hydrochemical composition of groundwater reflected different groundwater recharge mechanisms and influencing factors.Groundwater in the upper Bortala River area was mainly recharged by glacial snow melt water.The main sources of groundwater in the middle and lower reaches of the Bortala and Jing Rivers were surface water and precipitation,which were also greatly influenced by the nature of rock formations,farmland development and irrigation measures.Groundwater around Lake Ebinur Basin mainly came from snow and ice melt and precipitation.The middle and lower reaches and groundwater in the river and lake confluence areas are the key areas for pollution prevention and control and management.(3)Different hydraulic connections existed in underground aquifers.The electrical conductance(EC)of flow systemⅠranged from 210.00μS·cm^(-1)to 2500.00μS·cm^(-1),and the d-excess ranged from 6.47‰to 9.70‰.The EC of flow systemⅡranged from 141.60μS·cm^(-1)to 5260.00μS·cm^(-1),and the d-excess ranged from 9.61‰to 17.45‰.In conclusion,this study investigated the driving mechanisms of hydrogen and oxygen isotopes and water chemistry in groundwater in the Lake Ebinur Basin,which provided some theoretical reference for the rational use and scientific development of groundwater resources in the basin.