Hydrochemical and isotopic characteristics of groundwater in the northeastern Tennger Desert, northern China

Wang, Liheng; Dong, Yanhui; Xu, Zhifang; Qiao, Xiaojuan

Hydrochemical and isotopic characteristics of groundwater in the northeastern Tennger Desert, northern China | Les caractéristiques hydrochimiques et isotopiques des eaux souterraines du nord-est. du désert de Tennger, Chine du nord Características hidroquímicas e isotópicas del agua subterránea en el noreste del desierto de Tennger, en el norte de China 腾格里沙漠东北缘地区地下水化学与同位素特征研究 Características isotópicas e hidroquímicas das águas subterrâneas no nordeste do deserto de Tennger, Norte da China

2017

Wang, Liheng | Dong, Yanhui | Xu, Zhifang | Qiao, Xiaojuan

Groundwater is typically the only water source in arid regions, and its circulation processes should be better understood for rational resource exploitation. Stable isotopes and major ions were investigated in the northeastern Tengger Desert, northern China, to gain insights into groundwater recharge and evolution. In the northern mountains, Quaternary unconsolidated sediments, exposed only in valleys between hills, form the main aquifer, which is mainly made of aeolian sand and gravel. Most of the mountain groundwater samples plot along the local meteoric water line (LMWL), with a more depleted signature compared to summer precipitation, suggesting that mountain groundwater was recharged by local precipitation during winter. Most of the groundwater was fresh, with total dissolved solids less than 1 g/L; dominant ions are Na⁺, SO₄ ²⁻ and Cl⁻, and all mineral saturation indices are less than zero. Evaporation, dissolution and cation exchange are the major hydrogeochemical processes. In the southern plains, however, the main aquifers are sandstone. The linear regression line of δD and δ ¹⁸O of groundwater parallels the LMWL but the intercept is lower, indicating that groundwater in the plains has been recharged by ancient precipitation rather than modern. Both calcite and dolomite phases in the plains groundwater are close to saturation, while gypsum and halite can still be dissolved into the groundwater. Different recharge mechanisms occur in the northern mountains and the southern plains, and the hydraulic connection between them is weak. Because of the limited recharge, groundwater exploitation should be limited as much as possible.

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