Natural water input deposits little atmospheric carbon into groundwater in a desert

Fa, Keyu; Xie, En; Zhao, Xiao; Wang, Chaozi

Natural water input deposits little atmospheric carbon into groundwater in a desert

2021

Fa, Keyu | Xie, En | Zhao, Xiao | Wang, Chaozi

Anomalous CO₂ absorption by soils in drylands has been reported worldwide. It has been reported that atmospheric carbon can first be converted into soil dissolved inorganic carbon, and then be carried and rapidly sequestered in groundwater through irrigation (artificial water input). Nevertheless, the deposition rate may be inapplicable in drylands without artificial water input, and the fate of the atmospheric carbon may also be different. Here, we assessed the amount of the local rainfall, evaluated the elapsed time of the natural water infiltration and the feldspar weathering-induced carbon consumption rate, and analysed the characteristics of soil inorganic carbon in the Mu Us Desert, northwest China, where we have previously studied abiotic atmospheric carbon absorption and the soil water input mainly derives from precipitation. The results showed that, even with extreme precipitation, the inputted water could not rapidly transport carbon to the first aquiclude, indicating that natural water input cannot deposit the majority of the atmospheric carbon absorbed by soil into groundwater. Further analysis indicated that feldspar weathering might be able to rapidly consume most of the atmospheric carbon. The consumed carbon would be converted into pedogenic carbonate and conserved in subsoil due to the transportation of inputted water. These results can provide a basis for determining the fate of atmospheric carbon absorbed by soils in drylands.

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