CHEMISTRY AND LATE QUATERNARY EVOLUTION OF GROUND AND SURFACE WATERS IN THE AREA OF YABULAI MOUNTAINS, WESTERN INNER MONGOLIA, CHINA

Abstract

In the extensive area of western Inner Mongolia, China, the water demand of local residents often depends mainly on shallow aquifers, although scientific investigations of the quality and formation of the groundwater are still lacking. In this study the chemistry and isotopic composition of groundwater and lake water samples collected at 22 sites in the area of Yabulai Mountains (Fig. 1) in western Inner Mongolia were analysed. Chemical water analysis included the determination of Na+, K+, Ca2+, Mg2+, Li+, NH4+, Al3+, Co2+, CO32-, HCO3-, Cl-, SO42-, NO3-, F-, PO43-, HBO2 and SiO2, and 18O and tritium isotopes. Solute concentrations in groundwater show significant differences within the study area, while the water of the three lakes is dominated by sodium and chloride. This study reveals the importance of spatial variation of groundwater chemistry in an arid environment that has a relatively homogeneous lithological basement. The heterogeneity of groundwater chemistry suggests that the shallow groundwater in western Inner Mongolia is mainly recharged by infiltration of local rainfall. The relatively high tritium content indicates that the water in the shallow aquifer of the study area is generally not older than 100 years. Former shorelines in the lake basin of Shugui (Fig. 1) suggest the presence of a much larger lake in the past under a wetter climate than present hyper-arid conditions, presumably because of increased East Asian monsoon intensity during the middle Holocene. In the vicinity of commune administrations that have higher population density, the TDS of ground water is also higher, probably owing to water pollution. © 2005 Elsevier B.V. All rights reserved.