Origin of water in the Badain Jaran Desert, China: new insight from isotopes
To better understand the origin of water in the Badain Jaran Desert, China, water samples were collected from lakes, a spring and local unconfined aquifer for analyses of radiocarbon (<sup>14</sup>C), tritium (<sup>3</sup>H), stable hydrogen and oxygen isotope ratios (<...
Main Authors: | , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2017-09-01
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Series: | Hydrology and Earth System Sciences |
Online Access: | https://www.hydrol-earth-syst-sci.net/21/4419/2017/hess-21-4419-2017.pdf |
Summary: | To better understand the origin of water in the Badain
Jaran Desert, China, water samples were collected from lakes, a spring and
local unconfined aquifer for analyses of radiocarbon (<sup>14</sup>C), tritium
(<sup>3</sup>H), stable hydrogen and oxygen isotope ratios (<i>δ</i><sup>2</sup>H –
<i>δ</i><sup>18</sup>O), and <i>d</i>-excess values ( = <i>δ</i><sup>2</sup>H – 8<i>δ</i><sup>18</sup>O). A series of evaporation experiments were also conducted in the
desert to examine how the isotopic signature of water may change during
evaporation and infiltration under local environmental conditions. The
results show that the lakes in the southeastern sand dune area are fed by
groundwater discharging into the lakes and that local groundwater, on the
other hand, is derived primarily from modern meteoric precipitation in the
region. Although dissolved inorganic carbon (DIC) in groundwater yielded
very old radiocarbon ages, the presence of detectable amounts of tritium in
groundwater samples, together with their <i>δ</i><sup>2</sup>H, <i>δ</i><sup>18</sup>O
and <i>d</i>-excess characteristics, strongly suggests that the old radiocarbon ages
of DIC do not represent the residence time of water in the aquifer but are
the result of addition of old DIC derived from dissolution of ancient
carbonates in the aquifer. The data do not support the hypothesis that the
water in the Badain Jaran Desert was sourced in remote mountains on the
northern Tibetan Plateau. This study also finds no support for the
hypothesis that present-day water resources in the desert were recharged by
the precipitation that fell in the past during the early Holocene when the
climate was much wetter than today. Instead, this study shows that both
groundwater and lake water originated from meteoric precipitation in
the region including mountainous areas adjacent to the desert under the
modern climatic condition. |
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ISSN: | 1027-5606 1607-7938 |