Investigation of the sand sea with the tallest dunes on Earth: China's Badain Jaran Sand Sea

Comment on “Origin of water in the Badain Jaran Desert, China: new insight from isotopes” by Wu et al. (2017)

“…Recent work (Wang and Chen, 2018) found considerable overestimation of the groundwater age by the 14 C dating method due to neglect of dead carbon brought on by deep CO 2 emission. In contrast to the fossil groundwater hypothesis, the detectable tritium activities as shown by Wu et al (2017) and many others (Chen et al, 2006;Gates et al, 2008;Yang and Williams, 2003) indicate a modern precipitation source of the BJD groundwater. This suggests that the Qilian Mountains-sourced groundwater flows through hundreds of kilometers over only tens of years.…”

“…We have conducted work related to the 14 C dating and found the same problem with overestimation of the groundwater age (Chen et al, 2014;Wang and Chen, 2018). Wu et al (2017) reasoned that the average age of groundwater in the BJD should be much younger, since it includes modern meteoric water as indicated by tritium levels (Gates et al, 2008;Wu et al, 2017). They presented much evidence and discussion for their conclusion of groundwater recharged by modern precipitation from local areas.…”

“…However, the origin of the groundwater remains uncertain (Dong et al, 2013). Using stable and radioactive environmental isotopes, Wu et al (2017) investigated the connection between lakes and groundwater, and the origin of groundwater in the southeastern desert area.…”

“…They suggested that the BJD groundwater is derived primarily from modern meteoric water from local areas, including the southeastern adjacent small mountains. Based on isotopic evidence, the authors ruled out other hypotheses on the groundwater source, including fossil groundwater (Gates et al, 2008;Ma and Edmunds, 2006;Wang et al, 2015; and snowmelt from the Qilian Mountains, 500 km (center-to-center distance) southwest of the desert (Chen et al, 2004(Chen et al, , 2006.…”

Origin of water in the Badain Jaran Desert, China: new insight from isotopes

“…Because of the harsh environment and the lack of basic meteorological, climatic and geologic data in the desert, previous studies relied primarily on the isotope analyses of water samples collected from limited localities and times to draw inferences about the source and/or flow path of water in the area. It is generally agreed that groundwater is the main water source to the lakes and the groundwater inputs into the lakes balance the water loss due to intense evaporation as continuous groundwater discharge has been spotted around and under the lakes (Chen et al, 2012;Dong et al, 2013). However, the origin of groundwater in the desert remains a hotly debated issue (see review by Dong et al, 2013).…”