Hydrogeochemistry and fractionation of boron isotopes in the inter-dune aquifer system of Badain Jaran Desert, China

Abstract

Groundwater flow systems can be topography-controlled in arid, mountainous, and/or permeable areas. Previous theoretical studies indicated that local groundwater flow systems were usually less developed or even did not exist in recharge-controlled flow systems, and the whole flow system was dominated by regional groundwater flow system. However, the occurrence and role of local groundwater flow systems in real recharge-controlled aquifer systems are rarely addressed. The Badain Jaran Desert is featured by hyper dry climate, mega sand dune-lake landscapes, and highly permeable loose sediments, making it an ideal natural laboratory to address these issues. In this study, the local groundwater flow system and its interaction with saline lake water in the desert inter-dune aquifer are investigated via hydrogeochemical and isotopic approaches. The stable boron isotopic compositions reveal the existence of local groundwater flow systems in the hyper arid climate condition. The fresh local flow systems regulate not only the lake water volume and the lake water-groundwater mixing process, but also the ion contents and isotopic compositions of saline groundwater and lake water. Lake water-groundwater interaction manifests as fresh groundwater discharge and saline lake water intrusion. This study demonstrates that boron fractionation is applicable in deciphering groundwater flow patterns and lake water-groundwater interaction in the arid aquifer systems.