Issue 2, 2021

Hydrogeochemical characterization of a possible carbon sink from shallow saline–alkaline groundwater in the eastern Hetao Basin of Inner Mongolia in China

Abstract

The question of how saline–alkaline groundwater can be used as a CO2 sink in arid saline–alkaline areas remains controversial. This study investigates the role of saline–alkaline groundwater as a CO2 sink using a mass balance method, Gibbs diagrams of the hydrochemistry, and carbon isotope (δ13CDIC) measurements. Twenty-eight groundwater samples of varying electrical conductivity (EC; 1.52–52.34 mS cm−1) were collected at different depths (1–2 and 5–25 m) in the Hetao Basin of Inner Mongolia, China. The results showed that groundwater ions could be primarily concentrated from water–rock interactions and evaporation, and that there are two main groundwater types: a mixed Na·Ca·Mg–Cl·SO4·HCO3 type and a Na–Cl type. The dissolved inorganic carbon (DIC) concentration in samples obtained from a depth of 1–2 m was less than that in samples from 5–25 m, and a downward migration trend of DIC in the groundwater was observed. The DIC concentration exhibited a significant positive correlation with pH (R2 = 0.61, p < 0.05) and the saturation index of carbonates (R2 = 0.93, p < 0.01). Groundwater with a higher pH contained a higher DIC concentration and could provide strong carbon sink potential. The δ13CDIC values of the groundwater samples varied from −21.22‰ to −11.02‰, indicating that DIC was derived from the dissolution equilibrium of pedogenic carbonates and atmospheric/soil CO2. The carbon sequestration of the shallow saline–alkaline groundwater in the Hetao Basin could reach 4.66 × 108 g C a−1, which represents important potential of carbon sink in the biogeochemical cycle.

Graphical abstract: Hydrogeochemical characterization of a possible carbon sink from shallow saline–alkaline groundwater in the eastern Hetao Basin of Inner Mongolia in China

Article information

Article type
Paper
Submitted
27 Sep 2020
Accepted
05 Jan 2021
First published
07 Jan 2021

Environ. Sci.: Processes Impacts, 2021,23, 344-356

Hydrogeochemical characterization of a possible carbon sink from shallow saline–alkaline groundwater in the eastern Hetao Basin of Inner Mongolia in China

J. Yu, Y. Jiao, W. Yang, J. Yang and L. Liu, Environ. Sci.: Processes Impacts, 2021, 23, 344 DOI: 10.1039/D0EM00415D

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